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To address the challenge of performance portability and facilitate the implementation of electronic structure solvers, we developed the basic matrix library (BML) and Parallel, Rapid O(N), and Graph-based Recursive Electronic Structure Solver (PROGRESS) library. The BML implements linear algebra operations necessary for electronic structure kernels using a unified user interface for various matrix formats (dense and sparse) and architectures (CPUs and GPUs). Focusing on density functional theory and tight-binding models, PROGRESS implements several solvers for computing the single-particle density matrix and relies on BML. In this paper, we describe the general strategies used for these implementations on various computer architectures, using OpenMP target functionalities on GPUs, in conjunction with third-party libraries to handle performance critical numerical kernels. We demonstrate the portability of this approach and its performance in benchmark problems. [ABSTRACT FROM AUTHOR]

The synergistic effect between metals is of great significance for improving the performance of materials, but the mechanism of synergistic catalytic of bimetallic has rarely been reported in the hydrolysis of sodium borohydride (NaBH 4 , SB). In this paper, a flower shaped Co 2 FeO 4 catalyst with high catalytic performance was selected from a series of Co x M 3-x O 4 (M = Fe, Ni, Cu) catalysts by controlling the composition. Based on the results of XPS characterization and density functional theory (DFT) calculation, the influence of component control on catalytic performance was discussed and explained from the perspective of electronic structure, and the "valence band center" and "D-band center" descriptors were introduced into the SB hydrolysis reaction. The simulation analysis results showed that the synergistic effect between Co–Fe elements resulted in the smallest center shift of the D band, the smallest binding energy of the hydrolysis reaction, and the best promoting effect on the electronic structure, manifested as the best catalytic performance. The calculation results were consistent with the XPS characterization results and the experimental results of hydrolysis performance testing, revealing the principle of bimetallic synergistic effect on catalytic performance. The synergistic effect between metals is of great significance for improving the performance of materials, but the mechanism of synergistic catalytic of bimetallic has rarely been reported in the hydrolysis of sodium borohydride (NaBH 4 , SB). In this paper, a flower shaped Co 2 FeO 4 catalyst with high catalytic performance was selected from a series of Co x M 3-x O 4 (M = Fe, Ni, Cu) catalysts by controlling the composition. Based on the results of XPS characterization and density functional theory (DFT) calculation, the influence of component control on catalytic performance was discussed and explained from the perspective of electronic structure, and the "valence band center" and "D-band center" descriptors were introduced into the SB hydrolysis reaction. The simulation analysis results showed that the synergistic effect between Co–Fe elements resulted in the smallest center shift of the D band, the smallest binding energy of the hydrolysis reaction, and the best promoting effect on the electronic structure, manifested as the best catalytic performance. The calculation results were consistent with the XPS characterization results and the experimental results of hydrolysis performance testing, revealing the principle of bimetallic synergistic effect on catalytic performance. [Display omitted] • Flower-like Co 2 FeO 4 showed the best catalytic performance. • The "D-band center" and "valence -band center" of Co 2 MO 4 were studied. • Composition and electronic control improve the catalytic performance of Co 2 MO 4. • The adsorption configuration of H 2 O on the Co 2 MO 4 (311) surface was studied. [ABSTRACT FROM AUTHOR]

The Pauli kinetic energy functional and its functional derivative, termed Pauli potential, play a crucial role in the successful implementation of orbital-free density functional theory for electronic structure calculations. However, the exact forms of these two quantities are not known. Therefore, perforce, one employs the approximate forms for the Pauli functional or Pauli potential for performing orbital-free density functional calculations. In the present study, we developed a feed-forward neural network-based representation for the Pauli potential using a 1-dimensional (1-D) model system. We expanded density in terms of basis functions, and the coefficients of the expansion were used as input to a feed-forward neural network. Using the neural network-based representation of the Pauli potential, we calculated the ground-state densities of the 1-D model system by solving the Euler equation. We calculated the Pauli kinetic energy using the neural network-based Pauli potential employing the exact relation between the Pauli kinetic energy functional and the potential. The sum of the neural network-based Pauli kinetic energy and the von Weizsäcker kinetic energy resulted in an accurate estimation of the total kinetic energy. The approach presented in this paper can be employed for the calculation of Pauli potential and Pauli kinetic energy, obviating the need for a functional derivative. The present study is an important step in the advancement of application of machine learning-based techniques toward the orbital-free density functional theory-based methods. [ABSTRACT FROM AUTHOR]

Using the WIEN2k code, first-principles simulations of ZrXH 3 (X = Zn, Cd) hydride perovskites are performed to determine their hydrogen storage properties. The purpose of this study is to investigate their structural, optoelectronic, hydrogen storage, mechanical and thermoelectric properties. The structural analysis demonstrates their stability through the heat of formation along with desorption temperature and shows that these compositions belong to the orthorhombic space group Cmcm (no.63). The band structure and density of states are estimated for electronic characteristics, indicating the metallic nature of both compositions. Analysis of elastic properties such as elastic constants, Pugh's ratio, bulk modulus, Poisson's ratio, and anisotropy factor are explored to determine the mechanical stability of these compositions and demonstrate their suitability as a transport medium in hydrogen storage systems even at higher pressure. To study the optical behavior of the perovskites under consideration for hydrogen storage applications, the dielectric parameters, dielectric constants, refractive index, optical conductivity, absorptivity, and energy loss function are studied. The present paper represents the initial theoretical effort toward future exploration of these materials for hydrogen storage applications. [Display omitted] Using the WIEN2k code, first-principles simulations of ZrXH 3 (X = Zn, Cd) hydride perovskites are performed to determine their hydrogen storage properties. The purpose of this study is to investigate their structural, optoelectronic, hydrogen storage, mechanical and thermoelectric properties. The structural analysis demonstrates their stability through the heat of formation along with desorption temperature and shows that these compositions belong to the orthorhombic space group Cmcm (no.63). The band structure and density of states are estimated for electronic characteristics, indicating the metallic nature of both compositions. Analysis of elastic properties such as elastic constants, Pugh's ratio, bulk modulus, Poisson's ratio, and anisotropy factor are explored to determine the mechanical stability of these compositions and demonstrate their suitability as a transport medium in hydrogen storage systems even at higher pressure. To study the optical behavior of the perovskites under consideration for hydrogen storage applications, the dielectric parameters, dielectric constants, refractive index, optical conductivity, absorptivity, and energy loss function are studied. The present paper represents the initial theoretical effort toward future exploration of these materials for hydrogen storage applications. • Stability of ZrXH 3 (X = Zn, Cd) hydride perovskites is confirmed by Enthalpy of formation. • ZrXH 3 (X = Zn, Cd) hydride perovskites have high value of decomposition temperature. • The gravimetric hydrogen storage capacities comes out to be 1.89 % and 1.46 % respectively. • Metallic behavior is reveled by electronic structure of these hydrides. [ABSTRACT FROM AUTHOR]

Context: 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is a typical insensitive energetic material. It can be used in explosive formulations, such as PBX-9502 and LX-17-0. TATB is an intriguing and unusual explosive for another reason: it crystallizes into a wide array of planar hydrogen bonds, forming a graphite-like layered structure. Therefore, TATB is one of the important research objects, and its surface structure needs to be deeply understood. In this research work, the electronic and energetic properties of TATB (001) surface are explored. Methods: In this paper, the structural, electronic, energetic properties and impact sensitivity of TATB (001) surface structure at 0 and −3 GPa along with x-axis were calculated in this study using the first-principles calculations. The calculations in this paper are performed in the CASTEP code, which is based on the density functional theory with the first-principles calculation method using the plan-wave pseudopotential approach. The exchange-correlation interaction was adopted by the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional. The DFT-D method with the Grimme correction accurately models van der Waals interactions. To model the surface structures of TATB, the planar slab method was employed. We constructed TATB (001) periodic slabs including three layers with a 15-Å vacuum layer. [ABSTRACT FROM AUTHOR]

Context: The electronic properties and optical properties of Cr-doped monolayer WS2 under uniaxial compressive deformation have been investigated based on density functional theory. In terms of electronic structure properties, both intrinsic and doped system bandgaps decrease with the increase of compression deformation, and the values of the bandgap under the same compression deformation after Cr doping are reduced compared with the corresponding intrinsic states. When the compressive deformation reaches 10%, both the intrinsic and doped system band gaps are close to zero. New electronic states and impurity energy levels appear in the WS2 system when doped with Cr atoms. For the optical properties, the calculation and analysis of the dielectric function under each deformation regime of monolayer WS2 show that the compression deformation affects the dielectric function, and when the compression deformation is 10%, the un-doped and Cr-doped regimes show a decrease in ε1(ω) compared to the compression deformation of 8%. For each deformation system, the peak reflections occur in the ultraviolet region. Near the position where the second peak of the absorption spectrum appears, it can be seen that the ability of each system to absorb light gradually decreases with the increase of the amount of deformation and appears to be red-shifted to varying degrees. Methods: This study follows the initial principles of the density functional theory framework and is based on the CASTEP module of Materials-Studio software GGA and PBE generalizations are used to perform computations such as geometry optimization of the model. We have calculated the energy band structure of monolayer WS2 with intrinsic and compressive deformations of 2% and 4% using PBE and HSE06, respectively. The band gap values calculated using PBE are 1.802 eV, 1.663 eV, and 1.353 eV, respectively, and the band gap values calculated with HSE06 are 2.267 eV, 2.034 eV, 1.751 eV. The results show that the bandgap values calculated by HSE06 are significantly higher than those calculated by PBE, but the bandgap variations calculated by the two methods have the same trend, and the shape characteristics of the energy band structure are also the same. However, it is worth noting that the computation time required for the HSE06 calculation is much longer than that of the PBE, which is far beyond the capability of our computer hardware, and the purpose of this paper is to investigate the change rule of the effect of deformation on the bandgap value, so to save the computational resources, the next calculations are all calculated using the PBE. The Monkhorst–Pack special K-point sampling method is used in the calculations. The cutoff energy for the plane wave expansion is 400 eV, and the K-point grid is assumed to be 5 × 5 × 1. Following geometric optimization, the iterative precision converges to a value of less than 0.03 eV/Å for all atomic forces and at least 1 × 10−5 eV/atom for the total energy of each atom. The vacuum layer's thickness was selected at 20 Å to mitigate the impact of the interlayer contact force. [ABSTRACT FROM AUTHOR]

Context: In this paper, the structural stability, electronic structure, and optical properties of monolayer MoSe2 doped with C, O, Si, S, and Te atoms, respectively, under defective conditions are investigated based on first principles. It is found that the system is more structurally stable when defecting a single Se atom as compared to defecting a single Mo or two Se atoms. The electronic structure analysis of the system reveals that intrinsic MoSe2 is a direct bandgap semiconductor. The bandgap value of the system decreases with a single Se atom defect and introduces two new impurity energy levels in the conduction band. The defective systems doped with C and Si atoms all exhibit P-type doping. The total density of states of intrinsic MoSe2 is mainly contributed by the Mo-d and Se-p orbitals, and new density of state peaks appears near the conduction band after the defects of Se atoms. The total density of states of the defective system doped by each atom is mainly contributed by Mo-d, Se-p, and the result of the p orbital contribution of each dopant atom. By analyzing the dielectric function of each system, it is found that the intrinsic MoSe2 has the lowest static permittivity and the C-doped defect system has the highest static permittivity, which reaches 21.42. The C- and Si-doped defect systems are the first to start absorbing the light, and the intrinsic MoSe2 absorbs the light later, with its absorption edge starting at 1.25 eV. In the visible range, the reflection peaks of the systems move toward the high-energy region and the blue-shift phenomenon occurs. It is hoped that applying modification means to modulate the physical properties of the two-dimensional materials will provide some theoretical basis for broadening the application of monolayer MoSe2 in the field of optoelectronic devices. Methods: This study utilizes the first principle computational software package MS8.0 (Materials studio8.0) under density functional theory (DFT). The exchange–correlation potential (GGA-PBE) is described by the Perdew-Burke-Ernzerhof correlation function in CASTEP, and the potential function adopts the ultrasoft pseudopotential in the inverse space formulation. The plane wave truncation energy Ecut is set to 400 eV, the K-point is taken as 5 × 5 × 1, and the force convergence criterion is 0.05 eV/Å. The convergence accuracy of the total energy of the system is less than 1.0 × 10−5 eV/atom, the tolerance shift is less than 0.002 Å, and the stress deviation is less than 0.1 GPa. The vacuum layer is taken as 15 Å, which is intended to minimize the interlayer force. The vacuum layer was set to 15 Å to avoid the effect of layer-to-layer interaction forces in the crystal cell. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical properties, electronic structures, and thermodynamic properties of Ag2Ga and CuGa2 under pressure are studied using the first‐principles method based on Density functional theory (DFT). With the increase in pressure, the equilibrium lattice constants (a/a0 and c/c0) and volume ratio (V/V0) of Ag2Ga and CuGa2 continuously decrease. The elastic constants show that Ag2Ga and CuGa2 are mechanically stable under pressures of 0–20 GPa, and the increase in pressure improves their deformation resistance. The results of Young's modulus (E) show that the hardness of CuGa2 is higher than that of Ag2Ga. The results of Cauchy pressure (C12 ‐ C44) and B/G ratio show that the plasticity of Ag2Ga and CuGa2 can be maintained with the increase in pressure. By analyzing the density of states (DOS), charge density difference (CDD), and population, the influence of pressure on electronic structure is studied. The calculated Debye temperature (θD) shows that the covalent bond of CuGa2 is stronger. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the structural and magneto-electronic properties, and exchange coupling in new vanadium (V)-doped PbTiO3 perovskite oxide such as PbTi1−xVxO3 compounds with compositions of x = 0, 0.25, 0.5, 0.75, and 1. The calculations of these properties are based on density functional theory using the generalized gradient approximation of Wu-Cohen (GGA-WC) and the Tran-Blaha-modified Becke–Johnson potential (TB-mBJ). Our calculations with GGA-WC revealed that the lattice constant for PbTiO3 is in good concordance with other theoretical and experimental results, while for PbTi1−xVxO3 at x = 0.25, 0.5, 0.75, and 1, the lattice constant decreases with increasing vanadium concentration owing to the difference in sizes of Ti and V ionic radii. The improved electronic structures obtained by employing the TB-mBJ potential, demonstrated that the half-metallic ferromagnetic and half-metallic gaps are present in PbTi1−xVxO3 materials at x = 0.25, 0.5, 0.75, and 1, which makes them promising candidate materials for spintronics applications. [ABSTRACT FROM AUTHOR]

Vacancy engineering has repeatedly proven to be a powerful strategy for manipulating material properties. The important influence of selenium vacancies (V Se) on the physicochemical properties of rhenium diselenide (ReSe 2), exciting applications can be opened in areas such as catalysis and photoelectric devices. However, the effects of V Se on electronic structure, carrier lifetime, and electrochemical activity of ReSe 2 have remained inadequately explored and poorly elucidated. Herein, hydrothermal controlled growth of ReSe 2 with vacancy (V Se -ReSe 2) is used by different synthesis strategies, revealing its growth mechanism. An ethanol-assisted hydrothermal method based on carbon paper was used to adjust the V Se concentration by changing the time parameters. Mediated excitonic effects in the transient absorption (TA) spectroscopy and photoluminescence response of ReSe 2 regulated by V Se were characterized. The defect level (DL) leads V Se -ReSe 2 to produce a unique defect emission peak, and the V Se -mediated exciton dynamics problem was discussed. Moreover, the TA result of V Se -ReSe 2 shows that high V Se concentration prolongs carrier lifetime and causes high carrier separation efficiency and electron utilization. The electrocatalytic hydrogen evolution reaction of ReSe 2 catalyst revealed the ability of V Se concentration to regulate the electrochemical activity, which provides ideas for vacancy management catalyst performance. The presence of DL and the reduction of band gap are indicated by density functional theory, which confirms the regulatory effect of V Se concentration on the electronic structure of ReSe 2. This work proffers an optimal solution strategy for hydrothermal preparation of ReSe 2 , which demonstrates the feasibility of regulating electrochemical activity by vacancy engineering, and the excellent performance of V Se -ReSe 2 makes it show great potential in many fields such as water cracking and physical devices. [Display omitted] • A regulation strategy for the successful construction of V Se rich ReSe 2 nanoflowers was developed. • DFT investigated the reduction of the band gap and orbital contribution of ReSe 2 regulated by V Se. • Mediated excitonic effects in the TA and PL response of ReSe 2 regulated by V Se were analyzed. • The effectively regulate the HER activity of V Se -ReSe 2 were analyzed. Vacancy engineering is powerful for manipulating material properties. Selenium vacancies (V Se) exert significantly impact on the physicochemical properties of rhenium diselenide (ReSe 2), triggering applications in catalysis and photoelectric devices. However, the effects on electronic structure, carrier lifetime, and electrochemical activity are inadequately explored and poorly elucidated. Herein, hydrothermal-controlled growth of ReSe 2 with V Se is synthesized by different strategies. The ethanol-assisted hydrothermal method can adjust V Se concentration of ReSe 2 on carbon paper by time parameters. Mediated excitonic effects were characterized in the transient absorption spectroscopy and photoluminescence of V Se -regulated ReSe 2. The defect level produces unique defect emission peak, and the V Se -mediated exciton dynamics problem was discussed. The transient absorption result shows that high V Se concentration can optimize carrier lifetime, carrier separation efficiency, and electron utilization. The electrocatalytic hydrogen evolution reaction of ReSe 2 catalyst revealed the electrochemical activity regulation by V Se concentration, which provides ideas for enhancing catalyst performance. Density functional theory result confirms the role of selenium vacancies in the regulation of the electronic structure of ReSe 2. This work proffers an optimal solution strategy for hydrothermal preparation of ReSe 2 , and demonstrates the feasibility of regulating electrochemical activity by vacancy engineering. The excellent performance is beneficial for water cracking and physical devices. [ABSTRACT FROM AUTHOR]

The monoclinic semiconductor GeP is a new class of Group IV–V layered material, and it shows attractive anisotropic optical and electronic properties. In this paper, we investigate the structural and electronic evolution of layered GeP under pressure, using in situ x-ray diffraction, Raman and infrared spectra, and the density functional theory. All characterization methods reveal that the pressure causes two obvious phase changes. One isostructural transition is observed around 6 GPa. Above 21 GPa, another crystalline-to-amorphous transformation is obtained. It is worth noting that the high-pressure amorphous state can be retained at ambient conditions after the pressure is released. In addition, the pressure-induced red-shift of absorbance edge suggests its bandgap decreases with pressure. This result indicates that pressure has a significant effect on GeP. Meanwhile, it also provides a method for obtaining amorphous GeP, which is of interest to the energy storage community as it is a potential anode material for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

The sensing behaviors of monolayer antimonide phosphorus (SbP) for air pollutants (CO, CO2, H2S, SO2 NO, NO2 and NH3) are studied by using the density functional theory. In this paper, we computed the adsorption energy, charge transfer, adsorption distance, band gap, electronic structure and recovery time of gas molecules on monolayer SbP. The calculated results indicate that monolayer SbP is sensitive to SO2, NO and NO2 molecules via strong physical interaction. Through the analysis of charge transfer, it could be seen that there were more charges transfer of NO (0.549e), NO2 (− 0.366e) and SO2 (− 0.263e) gas molecules than other gases. When SO2, NO and NO2 gas molecules are adsorbed on the monolayer SbP, the band structure was reduced apparently. In particular, for NO2 adsorption, impurity bands pass through the Fermi surface, making the system appear semimetallic properties. Furthermore, the adsorption of NO and NO2 can cause obvious deviation in the DOS. On further analysis, we knew that these changes were mainly due to the orbital hybridization between the p orbitals of N, O and S atoms and the p orbitals of Sb and P atoms. Theoretical studies show that monolayer SbP may be a potential gas sensing material for SO2, NO and NO2 gas molecules. [ABSTRACT FROM AUTHOR]

In this paper, the atomic configuration, electronic structure, and work of adhesion for TiN(111)//B2‐NiTi(110) and TiN(111)//B19′‐NiTi(010) interfaces were investigated by first‐principles calculations based on density functional theory (DFT), which aim to provide a theoretical guidance for analyzing the service reliability of TiN films modified NiTi alloy devices. The results of this paper indicated that a hollow‐site stacking structure was formed on the interface when Ti and N were the terminal atoms on two sides. Such interfaces demonstrated a stronger bonding performance and a more stable structure than that with Ni and Ti as the terminal atoms. The work of adhesion of the TiN(111)//B19′‐NiTi(010) interface was 17.47 J/m2, which is greater than the work of fracture of TiN(111) (6.73 J/m2), whereas the work of adhesion of the TiN(111)//B2‐NiTi(110) interface was found to reach 5.49 J/m2, which is lower than the work of fracture of TiN(111). The models of the work of adhesion between the two interfaces indicate that there are significant bond strength changes in the TiN/NiTi interface, when the NiTi substrate undergoes martensitic transformation. The results of this paper contribute significantly to the service reliability analysis of TiN films coated on NiTi alloy devices. [ABSTRACT FROM AUTHOR]

The metal carbonyl clusters have been recognized as one of the most successful organometallic complexes with extensive catalytic applications. In this paper, we carried out a DFT study of the stability, electronic structure and thermodynamic properties of the intermediates [M3(CO)11] and [M3(CO)10] in the synthesis of [M3(2,3-bpp)(CO)10] (M=Ru and Os). CO binding energy analysis revealed that [M3(CO)10(μ-CO)], [Ru3(CO)8(μ-CO)2] and [Os3(CO)6(μ3-CO)2(μ-CO)2] are the most stables compounds due to the presence of bridge carbonyls which favor a covalent interaction. Sigma donation from the carbonyl to metal d orbital is the most significant contribution. Moreover, spectroscopic and computational studies indicated that [Ru3(2,3-bpp)(CO)10] is in good agreement with the analogues osmium complex. Regarding the pathway associated to the formation of [M3(2,3-bpp)(CO)10] we have found that the determinant step is the dissociation of a second CO axial into [M3(CO)10(μ-CO)]. Thus, unsaturated metal carbonyl intermediates exert a thermodynamic and kinetically control as consequence of the orbital reorganization. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HAP) is the main mineral component of bones and teeth. It is widely used in medicine as a bone filler and coating for implants to promote new bone growth. Ion substitutions into the HAP structure highly affect its properties. One of the most important substituents is magnesium. This paper presents new results obtained using high-precision hybrid density functional theory calculations for Mg/Ca substitutions in HAP in a wide magnesium concentration range within a 2 × 2 × 2 supercell model. Experimental data on the mechanochemical synthesis of HAP-Mg samples with different Mg concentrations are also presented. A comparison between the experiment and the theory showed good agreement: the HAP-Mg unit cell parameters and volume decreased with increasing degree of Mg/Ca substitution. The changes in the distances between the Ca and O, Ca and H, and Mg and O ions upon Mg/Ca substitution in different calcium positions was analyzed. The resulting asymmetry and distortion of the cell parameters were evaluated. It was shown that bulk modulus, energy levels, and band gap depend on the degree of Mg substitutions in the Ca1 and Ca2 positions. The formation energies of Mg/Ca substitutions showed non-monotonic behavior that was different for Ca1 and Ca2 positions. The Ca2 position had a slightly higher probability (~5 meV/f.u.) of substitution than Ca1 position at a Mg concentration x = 0.5. At x = 1, substitution in both positions can coexist. The simulated IR spectra for different Mg/Ca substitutions showed that Mg in the Ca2 position changes the IR spectrum more significantly than Mg in the Ca1 position. Similar changes were recorded in the IR spectra of the synthesized samples. The electronic structure is shown to be sensitive to the number and position of substitutions, which may be used to tweak the optical properties of the HAP-Mg material. [ABSTRACT FROM AUTHOR]

In this paper, the crystal structure and electronic structure of Ti 4 O 7 were calculated based on density functional theory, and Magnéli phase Ti 4 O 7 bulks were successfully prepared by spark plasma sintering (SPS). Results indicated that the contribution of Ti 3 d to Fermi level increased due to the lack of oxygen atom in lattice, and the energy band gap of Ti 4 O 7 was reduced compared with that of TiO 2. By calculating the relationship between the densification rate and effective stress in the process of SPS, it can be known that the densification mechanism of Ti 4 O 7 powders was controlled by diffusion. Based on this, under the conditions of sintering temperature of 1000 °C, holding time of 10 min and sintering pressure of 30 MPa, Ti 4 O 7 bulks with the optimal electrical conductivity (961.5 S cm−1) could be obtained, which was more than 30% higher than the graphite material reported in literature. The results reveals that Ti 4 O 7 will be one of the most promising electrode materials in the electrochemical field. [ABSTRACT FROM AUTHOR]

CsSe is reported as a half‐metallic ferromagnet compound which is optimized using the first principle calculation, but it is yet to prepared experimentally. CsCl‐type and NaCl‐type structures are preferred in literature to form from their electronic structures. Whether these two structures physically withstand or not is still unclear. Their mechanical properties can give a clear picture. The present study works in this direction and uncovers the mechanical perspective using DFT (Density Functional Theory) framework. The elastic stiffness tensor is obtained first, evaluated the mechanical parameters and then revealed how the mechanical formation is possible. Overall study elucidates to the evidence of why the CsSe compound occurs in CsCl‐type and how it has withstood at a room temperature using the elastic and mechanical properties through DFT. The stability of CsCl‐type has been confirmed from the phonon dispersion by DFPT (Density Functional Perturbation Theory) in this paper. The study also conducted the examination of the CsCl‐type's spintronic nature. [ABSTRACT FROM AUTHOR]

4 - Fluorophenol is a widely used aromatic compound and one of toxic organic pollutants, which has great harm to the environment and human body. It is of great significance to study its degradation mechanism under external electric field. In this paper, the density functional method ( DFT) and the time - dependent density universal method (TD - DFT) are used to study the geometric structure, spectral characteristics and dissociation characteristics of 4 - fluorophenol molecules under different applied electric fields ( 0 - 0. 03 a. u. ) at the B3LYP/ 6 -311 G + (2d,2p) basis set level. The results show that the applied electric field has a great influence on the structure and properties of 4 - fluorophenol molecules. With the increase of the external electric field in the direction of X ( C - F bond), the bond length of C - F bond of 4 - fluorophenol molecules increases, the total energy of molecular system gradually decreases, the dipole moment gradually increases and the energy gap gradually decreases. The strongest peak of the infrared spectrum of 4 - fluorophenol molecule is red - shifted, the peak value of the absorption peak of ultraviolet absorption spectrum first increases and then decreases, and the dissociation potential energy of 4 - fluorophenol molecule gradually decreases, which indicates that 4 - fluorophenol molecule tends to dissociate under the action of external electric field. This study provides a reference for the degradation of 4 - fluorophenol pollutant molecules by external electric field. [ABSTRACT FROM AUTHOR]

Computational study plays an important role to discover the potential of the bio-inspired nano scale molecular devices. Density Functional Theory (DFT) is one of the popular methods to calculate the properties of the molecules which can not be possible with ab initio process, preferably for transition metals. This method is important for electronic structure calculation along with structure of molecules, atoms and solids can also be calculated using this DFT method. It is the quantitative method to understand the material properties using the laws of fundamental quantum mechanics. The key benefit of Non Equilibrium Greens’ Function (NEGF) is that it preserves the wave character of the electrons, which leads to a extremely precise description of nanoscale. Combining theses DFT and NEGF calculation first principle approach reveal the quantumballistic properties of atomic scale electronic structures which is therefore attracts the researchers for their innovative calculations for nano scale device modelling. In this paper, we briefly discuss the review on various bio-molecular devices and their significances. Now-a-days bio inspired devices show more attractions due to their versatility compared to the conventional electronic devices. These nano scale devices are popular due to their performance, speed and high charge transmission properties compared to other conventional semiconductor devices. This review work presents some experimental works at the molecular level along with a variety of research works that are performed based on first principle approach. Several case studies prevails the importance of DFT and NEGF based first principle approach for nano scale device modelling. [ABSTRACT FROM AUTHOR]

Summary: In this paper, we present the first principle investigations for structural and optoelectronic properties of pure, n‐type, p‐type, and co‐doped MgSiP2 chalcopyrite compounds. To examine the structural and optoelectronic response, density functional theory (DFT) as embodied in Wien2k method is utilized. Within DFT, we have considered the exchange correlation functional prescribed by Perdew‐Burke‐Ernerhof generalized gradient approximation and Tran‐Blaha modified Becke Johnson for all computation presented in this paper. The results obtained from present calculations are in well reconciliation with previously reported experimental and theoretical data for pure compound, which affirms the accuracy of present computations. The electronic responses of all compounds are investigated through the crystal structure, energy band structure, and density of states. Optical responses of studied compounds are explained in terms of dielectric tensor, absorption, reflectivity, and refractivity spectra. Drastic change in energy band gap from pure (2.04 eV) to co‐doped compound (0.30 eV) is observed. The obtained band gaps and absorption range confirm the utility of these compounds in photovoltaic application. [ABSTRACT FROM AUTHOR]

Context: This paper presents the results of the study of the electronic structure and cationic and excited states of three spiroborate complexes (2-acetylacetonato-1,3,2-benzodioxaborol, its NH- and NMe-derivatives) and three corresponding ligands (acetylacetone, 4-aminopent-3-en-2-one, and 4-methylaminopent-3-en-2-one). Materials based on spiroborates are used in medicine, for example, as a drug carrier. In industry, spiroborate anions are used in ionic liquids and as alternative high performance lubricants. Analysis of experimental and calculated data allowed determining the influence of functional groups on the parameters of the electronic structure and energy of electronic transitions. Compared to acetylacetone and its NH- and NMe-derivatives, the upper filled molecular orbitals of the corresponding spiroborates are stabilized at 0.4–1.7 eV, which is due to the positive charge of the ligand due to the acceptor properties of the dioxyphenylene fragment. Among the studied compounds, when replacing the oxygen atom in the α-position with the NH- or NMe-group, a bathochromic shift of intense bands in the absorption spectra is observed, since the energy intervals between the orbitals of the π3 and π4 ligand are reduced. In addition, in a number of spiroborates, the violation of C2v symmetry when replacing an oxygen atom leads to the appearance of a low-intensity maximum in the long-wave part of the absorption spectrum, due to the π2X → π4 transition. Method: Complexes were studied by photoelectron spectroscopy, absorption spectroscopy, and high-level ab initio quantum chemical computations, including the algebraic diagrammatic construction method for the polarization propagator of the second order (ADC(2)), the outer-valence Green's function (OVGF), the density functional theory (DFT), the time-dependent density functional theory (TDDFT) and the domain-based local pair natural orbital (EOM-DLPNO) methods. X-ray photoelectronic spectra of two spiroborates in the condensed state were measured using a two-chamber high-vacuum system MXPS XP (Omicron, Germany). UV–visible absorption spectra were recorded using a spectrophotometer 2550 (Shimadzu-UV, Japan). The geometry of all studied compounds was optimized by the DFT/B3LYP/Def2-SVP method. The energy of electron levels in the S0 state and the distribution of electron density at each MO were obtained by the DFT/CAMB3LYP/cc-pVDZ method. The energies of excited states were obtained by the TDDFT/CAMB3LYP/cc-pVDZ, ADC(2)/cc-pVDZ and EOM-DLPNO/cc-pVDZ methods. All DFT and TDDFT calculations were carried out in the GAMESS (US) software computing package. ADC(2) calculations of excited states were performed using the Orca 4.0.1 software package. EOM-DLPNO and OVGF calculations were carried out in the Gaussian 16 software package. [ABSTRACT FROM AUTHOR]

The substitution position of indium (In) atoms is significant for developing novel orthorhombic GaN hydrogen storage materials. Currently, research on the influence of In atom substitution position on the orthorhombic GaN is still relatively limited. In this paper, based on the first-principles, formation energy, electronic structure, elastic properties, and mechanical stability of InGaN materials with different In atom substitution positions were studied. The results show that the formation energy of In atom substitution position separated by three atoms is the smallest, and the structure is most easily formed. Under the same doping conditions, the InGaN materials with this structure also have larger band gap and smaller elastic modulus, bulk modulus, shear modulus, and elasticity modulus, which means that its compressive strength and shear stress are slightly weaker, and its toughness and hardness are lower. In addition, the calculation results of phonon spectrum show that the InGaN material with three atoms interval also has good mechanical stability under ambient pressure. This study provides a theoretical basis for studying new hydrogen storage metamaterials with orthorhombic GaN. [ABSTRACT FROM AUTHOR]

With the development of industrialization, the use of mercury in industry has become more and more widespread, causing serious impacts on the environment. It is therefore urgent to find new effective ways to combat mercury pollution. In this paper, The effect of C, O, P, Ni and Au doping on the adsorption of Hg atoms by WS 2 has been investigated based on the first nature principle of density functional theory. The electronic structures and optical properties of the adsorbed systems were calculated after atomic doping. The results show that the absolute value of the adsorption energy of the intrinsic adsorption system is small and does not favour the adsorption of Hg on WS 2. However, after C, P, Ni and Au doping, the adsorption energy of the system is significantly increased and a strong charge transfer between WS 2 and Hg atoms occurs, as well as a significant change in the band gap of the structure. This suggests that atomic doping favors the adsorption of Hg by WS 2. The effect of O doping on the adsorption system is not significant. In addition, a study of the optical properties revealed that the static dielectric constants of the system appeared to increase to varying degrees after the doping of the atoms. The doping of P, Ni and Au atoms increases the light absorption coefficient and contributes to the photocatalytic efficiency of the structures. The doped atoms cause a red shift in the reflectivity peak of the adsorbed system. In summary, the doping of C, P, Ni and Au enhances the adsorption of Hg atoms on WS 2. O doping has less effect on the adsorption of Hg on WS 2. • In this paper, the effect of C, O, P, Ni and Au doping on the adsorption of Hg atoms by WS2 was investigated. • The results show that atomic doping favors the adsorption of Hg by WS2. • Atomic doping alters the electronic properties of the structure. • Atomic doping alters the optical properties of the structure. [ABSTRACT FROM AUTHOR]

We propose an unconditionally energy-stable, orthonormality-preserving, component-wise splitting iterative scheme for the Kohn-Sham gradient flow based model in the electronic structure calculation. We first study the scheme discretized in time but still continuous in space. The component-wise splitting iterative scheme changes one wave function at a time, similar to the Gauss-Seidel iteration for solving a linear equation system. At the time step n , the orthogonality of the wave function being updated to other wave functions is preserved by projecting the gradient of the Kohn-Sham energy onto the subspace orthogonal to all other wave functions known at the current time, while the normalization of this wave function is preserved by projecting the gradient of the Kohn-Sham energy onto the subspace orthogonal to this wave function at t n + 1 / 2. The unconditional energy stability is nontrivial, and it comes from a subtle treatment of the two-electron integral as well as a consistent treatment of the two projections. Rigorous mathematical derivations are presented to show our proposed scheme indeed satisfies the desired properties. We then study the fully-discretized scheme, where the space is further approximated by a conforming finite element subspace. For the fully-discretized scheme, not only the preservation of orthogonality and normalization (together we called orthonormalization) can be quickly shown using the same idea as for the semi-discretized scheme, but also the highlight property of the scheme, i.e., the unconditional energy stability can be rigorously proven. The scheme allows us to use large time step sizes and deal with small systems involving only a single wave function during each iteration step. Several numerical experiments are performed to verify the theoretical analysis, where the number of iterations is indeed greatly reduced as compared to similar examples solved by the Kohn-Sham gradient flow based model in the literature. • This paper proposes a novel and efficient numerical scheme for the Kohn-Sham gradient flow based model. • The scheme is an unconditionally energy-stable, orthonormality-preserving, component-wise splitting iterative scheme. • The scheme does not modify the original energy, allows large time step sizes, and solves small systems at each time step. • The rigorous proof is presented in the paper. • Several numerical examples are illustrated to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

Scale formation causes major losses in oil wells, related to production and equipment damages. Thus, it is important to develop effective materials to prevent scale formation and inhibit any additional formation. One known environmentally friendly material with promising performance for scale inhibition is polyepoxysuccinic acid (PESA). However, the performance and further development of any scale treatment chemical is highly affected by its electronic structure and behavior. Thus, this paper aims to obtain insights into the kinetics and thermodynamics of the chemical reactions during scale inhibition by investigating the geometrical and electronic structure of PESA. Density Functional Theory (B3LYP/6–31 g (d)-lanl2dz) was used to study the structure of PESA, considering different forms of PESA and their corresponding binding affinities and chemical behaviors. The scale is represented as FeII ions, and PESA is modeled as (n = 1, and 2). Three conditions of PESA were considered: the standard form, the form with a modified electron donating group (R- = CH3-), and ammonium salt of PESA (M+ = NH4+). The results showed that PESA has a high binding affinity to FeII, comparable to known chelating agents, with the highest binding affinity for ammonium salt of PESA with the CH3- donating group (−1530 kJ/mol). The molecular orbitals (MO), electron affinity (EA), and charge analysis further explained the findings. The HOMO-LUMO gap and EA results revealed the high reactivity and thermodynamic stability of all forms of PESA. In addition, the ammonium salt form of PESA with the electron donating group performs better, as it has a greater overall negative charge in the compounds. Furthermore, the NH4+ cationic group tends to lower the value of the HOMO orbital, which increases the inhibition performance of PESA. [ABSTRACT FROM AUTHOR]

Graphene has been widely studied in many fields due to its excellent physical and chemical properties. In this paper, we focus on the electronic structure and adsorption behavior of Al atoms and X (X = B , N, Si, S) atoms co-adsorption on the surface of pure graphene and Al atom adsorption on the surface of X (X = B , N, Si, S) atoms-doped graphene systematically. The adsorption energy, adsorption distance, bond length, bond angle, and electronic structure were studied using density functional theory (DFT) theoretical calculation. The results show that the adsorption capacity of (Al, X) atoms co-adsorbed on the graphene surface is significantly improved compared to the Al atoms on the pure graphene surface. The adsorption energy of Al and B atoms co-adsorbed on the graphene surface is basically the same as that of Al atoms on the B-doped graphene surface. The calculation results also show that the adsorption capacity of Al atoms and X (X = N , Si, S) atoms co-adsorbed on the surface of graphene is better than that of Al atoms on the surface of graphene doped with X (X = N, Si, S) atoms. Compared with N atom and S atom-doped systems, the Si-doped graphene surface has a stronger adsorption capacity for Al atoms than pure graphene. However, due to the doping of N and S atoms, the adsorption capacity of Al atoms on the graphene surface is somewhat reduced. Our calculation results provide a theoretical basis for further selection of Al-based graphene composite materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • The porous few-layer bimetallic co-doped g-C 3 N 4 is prepared via a facile bottom-up method. • The bimetallic synergetic regulating effect on the electronic structure can be produced in Co/Ni-g-C 3 N 4. • The superior performance results from the improved charge separation efficiency and visible light harvestability. • This work provides meritorious guidance for new bimetallic co-doped g-C 3 N 4 photocatalysts. The low specific surface area and low charge transfer efficiency of conventional graphite carbon nitride (g-C 3 N 4) are the main obstacles to its application in photocatalytic CO 2 reduction. In this paper, graphite carbon nitride was protonated by phosphoric acid (H 3 PO 4), and a new few-layer porous carbon nitride was prepared by intercalation polymerization with doping bimetal in the cavity of g-C 3 N 4. Under visible light irradiation, the CO formation rate of Co/Ni co-doped g-C 3 N 4 can reach 13.55 μmol g−1 h−1, which was 3.9 times higher than that of g-C 3 N 4 (3.49 μmol g−1 h−1). The density functional theory (DFT) calculations showed that the addition of Co and Ni in the cavity of g-C 3 N 4 can induce bimetallic synergistic regulation of the electronic structure, thus improving the separation efficiency of charges and visible light capture ability of g-C 3 N 4. Our work has great reference value for designing and synthesizing novel bimetallic co-doped g-C 3 N 4 photocatalytic materials. [ABSTRACT FROM AUTHOR]

Since the discovery of graphene, various two-dimensional materials with novel properties have attracted more and more attention. Janus two-dimensional materials have asymmetric surface properties. These special structures often have peculiar electrical, magnetic and optical properties, which have become a research hotspot in the field of material science in recent years. In this paper, the structures of Janus two-dimensional materials CrXX'(X/X'= S,Se,Te)(CrSSe, CrSTe, CrSeTe) were built, their electronic, magnetic, optical properties were studied, and the effect of biaxial strain on above properties was studied. In terms of electronic structure, the results show that CrSSe, CrSTe and CrSeTe are metallic and excellent conductors of electrons. Biaxial strain does not change their metallicity, which means their electronic structure has good robustness. In terms of magnetic properties, due to the contribution of unpaired electrons in the 3d orbital of Cr atom, CrXX'(X/X' = S,Se,Te) have long range magnetic ordering. By applying tensile strain, their magnetic moments increase, and by applying compressive strain, their magnetic moments decrease. In addition, CrXX'(X/X' = S,Se,Te) have higher Curie temperature. The Curie temperature of CrSSe is 165 K, that of CrSeTe is 195 K, and that of CrSTe is 310 K, which is above the room temperature. For optical properties, the results show that CrXX'(X/X' = S,Se,Te) have excellent absorption capacity of visible and ultraviolet light, which is about 50% higher than that of typical light absorption material graphene. Their light absorption coefficients can be adjusted by applying strain, compressive strain and tensile strain can move the absorption spectrum to short wave and long wave respectively. In conclusion, this work provides theoretical guidance for the further study of the application of two-dimensional monolayer CrXX' (X/X' = S,Se,Te) in the field of new room temperature spintronic devices. [ABSTRACT FROM AUTHOR]

This paper employs the Heyd-Scuseria-Ernzerhof (HSE) function to research electronic structures of monolayer InxAl1-xN with different compositions (x = 0, 0.25, 0.5, 0.75, 1) based on the first-principles, and the optical properties of singlelayer InxAl1-xN are calculated by Generalized Gradient Approximation-Perdew Burke Ernzerhof (GGA-PBE) function. The influence of the electronic structure on the properties has been analyzed. Then the influence of doping quantity on the characteristics has been summarized, which also indicates the trend of the complex dielectric function and absorption spectrum. The calculation results show that with the increase of x, the static dielectric constant increases, the electron transition ability increases, and the absorption peak intensity in the light absorption spectrum increases. It can conclude that the InxAl1-xN compound can theoretically achieve the adjustable Eg and photoelectric performance with x, which will apply in making various optoelectronic devices, including solar cells and sensors. [ABSTRACT FROM AUTHOR]

The bulk properties such as lattice constants, bulk moduli, and cohesive energies of alkali, alkaline-earth, and transition metals are studied within the framework of the recently developed meta-GGA (meta-Generalized Gradient Approximation) level semilocal exchange-correlation functionals. To establish the applicability, broadness, and accuracy of meta-GGA functionals, we also put the results obtained using PBE (Perdew-Burke-Ernzerhof) [J. P. Perdew et al., Phys. Rev. Lett. 77, 3865 (1996)] and PBE reparameterized for solid [J. P. Perdew et al., Phys. Rev. Lett. 100, 136406 (2008)] GGA functionals. The interesting feature of the present paper is that it measures the accuracy of the recently developed TM (Tao-Mo), TMTPSS [TM exchange with Tao-Perdew-Staroverov-Scuseria (TPSS)] [J. Tao and Y. Mo, Phys. Rev. Lett. 117, 073001 (2016)] correlation, and strongly constrained and appropriately normed [J. Sun et al., Phys. Rev. Lett. 115, 036402 (2015)] functionals to calculate the aforementioned properties. Not only that, we also include other (popular) meta-GGA functionals in order to have a closer look at the performance of the meta-GGA functionals too. The present systematic investigation shows that the TM functional is accurate in describing the lattice constants while for cohesive energies and bulk moduli, the PBE and modified TPSS perform better compared to others. [ABSTRACT FROM AUTHOR]

This paper presents a computational method for the estimation of the highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) of metallic nano-clusters using efficient density functional computations with the high accuracy of the GW method. Electronic structures of magnesium nano-clusters Mgn (n = 1–22, 25, 30, 35, and 40) are computed using the density functional theory (DFT) and the quasiparticle GW method. It is found that the energy difference between the DFT and GW results, defined as the scissors operator or correction, is only dependent on the cluster size and independent of the electronic shell filling effect. The scissors operators of HOMOs and LUMOs of metallic clusters can thus be fitted by using simple power functions of the cluster size n. Therefore, the HOMOs and LUMOs of metallic clusters can be efficiently calculated using DFT with a modification of scissors operators. The scissors operators are also demonstrated to be applicable to occupied and unoccupied states near the Fermi level. [ABSTRACT FROM AUTHOR]

[Display omitted] • Doping B, N, P can enhance the electrical conductivity and adsorption properties of GeC monolayers. • The stability of the three adsorption structures was in the order of C2H2 > CH4, and the increase of Qt and the decrease of bandgap indicated that the conductivity of the adsorbed system was improved. • it was shown that the monolayer of P-GeC has the most optimal adsorption behaviour and reusability for C2H2. In this paper, the stability, electronic structure and optical properties of monolayer GeC, B, N and P doped GeC systems are systematically investigated based on the first principles of density functional theory. The results show that the results show that the intrinsic GeC monolayer has a weak adsorption capacity for CH 4 and C 2 H 2 , which is unfavourable for the sensing and trapping of CH 4 and C 2 H 2 gases. Based on calculated adsorption distance, adsorption energy and charge transfer, we find that P-GeC monolayer is the most sensitive to CH 4 and C 2 H 2 molecules, and the most of gas molecules act as acceptors to gain electrons from GeC monolayer. The adsorption energy of CH 4 is smaller than that of C 2 H 2 gas molecule, which implies that C 2 H 2 is more easily desorbed from P-GeC. Moreover, the work function changes significantly when gas molecules adsorbed on B, N, P-GeC, and Recovery times indicate that B, N and P doped GeC monolayers are more selective and sensitive to C 2 H 2 molecules compared to CH4 molecules. The research work aims to provide a theoretical basis for the application of GeC-based gas sensors, and P-doped GeC monolayers can be used as candidate materials for C 2 H 2 gas sensing and trapping. [ABSTRACT FROM AUTHOR]

[Display omitted] • Molar diamagnetic susceptibility values for some amino acids are reported for the first time. • The results obtained are evaluated in terms of electronic structure principles. • Molar diamagnetic susceptibility can be used in the introducing new chemical hardness, polarizability and entropy scales. One of the main aims of the theoretical chemists is to introduce new and useful approaches for the estimation of chemical reactivity descriptors of Conceptual Density Functional Theory (CDFT) like absolute hardness, polarizability and magnetizability. In addition to providing results close to experimental results, the methods developed for this purpose must also be easily applicable to many molecular systems and easy to learn. "Property Prediction from Structural Differences" method proposed by one of the authors of this article is based on the idea that various properties of molecules can be easily calculated by taking the sum of the functional group contributions in the structure of the molecule. The most important thing in the applying of the method is the reliable determination of functional group contributions. In the present paper, using "Property Prediction from Structural Differences" method, we predicted the molar diamagnetic susceptibilities of amino acids with reasonably good accuracy. The computed values are in good agreement with experimental data and the results of previously introduced theoretical models. The reason why amino acids were especially preferred in the study is the lack of the molar diamagnetic susceptibility data of some amino acids in the literature. Additionally, to test whether a molar diamagnetic susceptibility based scale can be proposed for the calculation of any CDFT based reactivity descriptor, DFT computations were also performed for amino acid molecules. The relationships between parameters were evaluated in terms of the electronic structure rules like Maximum Hardness, Minimum Polarizability, Minimum Magnetizability and Minimum Electrophilicity Principles. [ABSTRACT FROM AUTHOR]

In this paper, based on the first-principles calculation of density functional theory, the adhesion work, interface energy and electronic structure of Ag/Ti 3 AlC2 interface are systematically studied. In the calculation process, 18 interface models with different terminals and different stacking sequences are considered. After comparing the calculation results, it is found that the interface model of Al terminal is the most stable among the six interface models of Ti1(C), Al, C(Ti2), Ti2(Al), C(Ti1) and Ti2(C). After changing the stacking order of Al terminal interface atoms, it can be found that the order of interface stability of Al terminal is HCP > FCC > OT according to the interface energy, and the interface energy of HCP interface model is 2.209J/m2. After the comprehensive analysis of adhesion work, interface energy and electronic structure, it is found that the theoretical calculation results are consistent with the previous experimental results. Al atoms have a tendency to move to the Ag matrix and form Ag (Al) solid solution, and the formation of solid solution further increases the stability of the interface. • Compared with the previous calculation method and improve the calculation details. • The stability of the interface structure is determined by calculation. • The calculation results are in good agreement with the experimental results, which proves the accuracy of the calculation. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenides (TMDs) such as MoS 2 and WS 2 have traditionally been used, but Group-10 TMDs have recently attracted attention due to their small and tunable band gap and high mobility. This paper investigates the impact of vacancy and strain on the structure of hexagonal single-layer PdSe 2 using density functional theory (DFT) calculations. The sublayers can introduce strain into the structure when building these 2D surfaces. Structures with chalcogen vacancies are more stable than those with metallic vacancies. When Se atoms are removed, the band gap disappears, and the semiconductor phase changes from semiconductor to conductor. The band gap can be recreated by applying a suitable percentage of strain using the vacancy mode. The work function (WF) was also calculated. WF decreases with compressive strain but increases with Se removal and tensile strain. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) is the most successful and widely used approach for computing the electronic structure of matter. However, for tasks involving large sets of candidate molecules, running DFT separately for every possible compound of interest is forbiddingly expensive. In this paper, we propose a neural network based machine learning algorithm which, assuming a sufficiently large training sample of actual DFT results, can instead learn to predict certain properties of molecules purely from their molecular graphs. Our algorithm is based on the recently proposed covariant compositional networks framework and involves tensor reduction operations that are covariant with respect to permutations of the atoms. This new approach avoids some of the representational limitations of other neural networks that are popular in learning from molecular graphs and yields promising results in numerical experiments on the Harvard Clean Energy Project and QM9 molecular datasets. [ABSTRACT FROM AUTHOR]

In this paper, eight complexes M-1, M-2, M-3 and M-4 (M = Ir or Rh) in the general formula [M(C^N)2(N^N)] (C^N = cyclometalated ligands and N^N = ancillary ligands) are systematically investigated by density functional theory (DFT) and time-dependent DFT methods. With the aim to study the influence of metal centers for nonlinear optical (NLO) responses, the geometrical and electronic structures, first hyperpolarizabilities (βtot) and UV-Vis absorption spectra are investigated in detail. It is found that the βtot values increase 1.8–3.7 times as the metal atom changes from Rh to Ir. Among all the studied complexes, Ir-3 (C^N = 4-chloro-2-phenylquinoline with N^N = 2,9-dimethyl-1,10-phenanthroline) shows the highest βtot value with an amplitude of 2415.4 a.u. computed at the ωB97XD/6-31G+(d)/SDD level, which can be seen as a promising candidate for second-order NLO materials. In addition, the HOMO energy levels increase upon increasing the size of the metal atom, which contributes to a significant reduction in HOMO–LUMO gaps. The βtot values and HOMO–LUMO gaps are in an inverse relationship. Furthermore, tuning the center metals Ir/Rh can be seen as an effective method to modulate the charge transfer degree. We anticipate that this study may serve as a new strategy for the rational design and synthesis of second-order NLO materials. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis and structural characterisation of two hetero-metallic clusters, [(CO)3CrSn5Cr(CO)3]4− and [(CO)3MoSn5Mo(CO)3]4−, both of which have a pentagonal bipyramidal core. The structures are similar to that of previously reported [(CO)3MoPb5Mo(CO)3]4− and our analysis of the bonding suggests that they are best formulated as containing Sn54− rings bridging two zerovalent M(CO)3 fragments. The electronic structure is compared to two isolobal M2E5 clusters, [CpCrP5CrCp]− and Tl77−, both of which show clear evidence for trans-annular bonds between the apical atoms that is not immediately obvious in the title clusters. Our analysis shows that the balance between E-E and M-M bonding is a delicate one, and shifts in the relative energies of the orbitals on the E5 and M2 fragments generate a continuum of bonding situations linked by the degree of localisation of the cluster LUMO. [ABSTRACT FROM AUTHOR]

In this paper, the first principle method based on density functional theory is used to calculate the electronic structure, magnetic moment, and charge density and differential charge density of the thin film growth system whose epitaxial relation is CoSi (001)//MgO (001). The results show that when the lattice constants a and b of CoSi crystal are set as 0 .84224 nm and C =0.28135 nm, the energy of the system is the lowest and the most stable equilibrium state is reached. It can be seen from the spin polarization band diagram, total electron state density and fractal density that the guide band bottom and valence band top of the CoSi epitaxial film overlap significantly, thus showing the gold property and producing obvious spin cracking phenomenon near the Fermi level. The valence band top is mainly composed of THE 3d7 state electrons of Co, while the conduction band bottom is mainly composed of the 3p state electrons of Si. At the same time, it can be seen from the state density that the phenomenon of pseudo energy gap is generated. The Co-3d state electrons not only mainly contribute to the state density, but also are speculated to be the main factor for the magnetic generation of the film. According to the calculated Mulliken charge and charge density, electrons are transferred from Si to Co, and Co ACTS as the electron acceptor, forming an anti-bonding state between Co and Si, and forming a covalent bond structure between Co and Si. The CoSi under this epitaxial relationship is ferromagnetic and the total magnetic moment is 0.52 μB. [ABSTRACT FROM AUTHOR]

In this paper, the first-principles method based on density functional theory was used to study the electronic structure and optical properties of germanene at different warpage, and the influence of warpage on electronic structure and optical properties was analyzed. Six different approximation methods were used to optimize the geometric structure of germanene, and the most stable structure system was obtained. On this basis, different warping structures were selected, and the stability of warping degree was demonstrated, and three stable warping structures were obtained. The band gap of germanene is opened by adjusting the warping degree, and the conversion between indirect band gap and direct band gap is realized by adjusting the warpage. The regulation mechanism of band structure and the effect of warpage on the optical properties of germanene are explained by analyzing the density of states. The results show that the warpage can effectively regulate the electronic structure and optical properties of germanene, and improve the photoelectron utilization efficiency. [ABSTRACT FROM AUTHOR]

In this paper, we propose and analyze a gradient flow based model for electronic structure calculations. First, based on an extended gradient flow proposed in this paper, we propose a Kohn--Sham gradient flow based model. We prove that our gradient flow based model is orthogonality preserving, the extended gradient has an exponential decay over time t, and the equilibrium point is a local minimizer of the Kohn--Sham energy functional. Then we propose a midpoint scheme to carry out the temporal discretization, which is proven to be orthogonality preserving, too. Based on the midpoint scheme, we design a practical orthogonality preserving iteration scheme which can deal with the propagation of the gradient flow based model and prove that the scheme produces approximations that converge to a local minimizer with some convergence rate under some reasonable assumptions. Finally, we report a number of numerical experiments that validate our theoretical results. [ABSTRACT FROM AUTHOR]

Two-dimensional layered materials represented by MoS2 and GeS exhibit excellent physical properties in optical and electrical aspects. How to combine the excellent properties of the two materials and obtain composite materials with new synergistic functions are of great significance to the development and application of electronic devices. This work uses the first principles calculation method of density functional theory to systematically study the electronic structures and optical properties of GeS / MoS2 heterojunctions, at the same time, the influence of interface distance, strain and electric field on the electronic structures and the optical properties of the heterojunctions was also explored. The research results show that the GeS / MoS2 heterojunctions is a type Ⅱ band arrangement, which is conducive to the separation of photogenerated electron-hole pairs. Further research found that the band arrangement and light absorption coefficient of GeS / MoS2 heterojunctions can be effectively controlled by means of strain and electric field. The research results show that GeS / MoS2 heterojunctions has potential applications in photocatalysis, optoelectronic devices and other fields, and the research in this paper provides theoretical guidance for the design and preparation of GeS / MoS2 related optoelectronic devices. [ABSTRACT FROM AUTHOR]

The stability, electronic structures, work function, and optical properties of single-layer g-C3N4 and X/ g-C3N4 (X = g-C3 N4 , AlN and GaN) heterostructures were investigated using plane-wave density functional theory with ultra-soft pseudopotentials. The results show that the lattice mismatch ratio and lattice mismatch energy of X/ g-C3N4 heterojunction are very low, indicating that X/ g-C3N4 heterojunction has excellent stability. Compared with the single-layer g-C3N4, the bandgap of the X/ g-C3N4 all reduces, and the peaks and troughs of the density of states greatly improves. At the same time, X/ g-C3N4 has a redshift, which leds to an increase in the number of electrons in the excited state, making electronic transitions easier. It shows that the heterojunction is beneficial to improves the response-ability of the system to visible light, and effectively improves the photocatalytic activity of the system. Further calculations show that the work function of X/ g-C3N4 reduces and a built-in electric field is formed at the interface, which inhibits the recombination of photo-generated electron-hole pairs. This is of great benefit to the migration of carriers and the improvement of photocatalytic ability. Among them, the GaN/ g-C3 N4 heterojunction has the smallest work function, the potential difference at the interface formed a built-in electric field and the redshift is the most obvious. It can be inferred that the GaN/ g-C3 N4 heterojunction has the best photocatalytic activity. Therefore, the heterojunction proposed in this paper is an effective means to improve the photocatalytic activity of the system. [ABSTRACT FROM AUTHOR]

In this paper, Cr oxygenated species dispersed on Pt nanowire assemblies (PtCrOX NWs) were successfully prepared for the methanol oxidation reaction by a metal precursor dilution strategy. Notably, the PtCrOX NWs catalyst exhibits excellent performance for electrocatalytic methanol oxidation. Density functional theory results revealed that the doped Cr oxygenated species, which moderated the electronic structure of the Pt atoms, can significantly decrease the free energy of COOH* formation, thus leading to superior methanol oxidation performance. [ABSTRACT FROM AUTHOR]

In this paper, we employ an evolutionary algorithm along with the full-potential density functional theory (DFT) computations to perform a comprehensive search for the stable structures of stoichiometric (WS2)n nano-clusters (n = 1 - 9), within three different exchange-correlation functionals. Our results suggest that n = 5 and 8 are possible candidates for the low temperature magic sizes of WS2 nano-clusters while at temperatures above 500 Kelvin, n = 7 exhibits a comparable relative stability with n = 8. The electronic properties and energy gap of the lowest energy isomers were computed within several schemes, including semilocal Perdew-Burke-Ernzerhof and Becke- Lee-Yang-Parr functionals, hybrid B3LYP functional, many body based DFT+GW approach, ΔSCF method, and time dependent DFT calculations. Vibrational spectra of the lowest lying isomers, computed by the force constant method, are used to address IR spectra and thermal free energy of the clusters. Time dependent density functional calculation in a real time domain is applied to determine the full absorption spectra and optical gap of the lowest energy isomers of the WS2 nano-clusters. [ABSTRACT FROM AUTHOR]

Accurate and computationally efficient exchange-correlation functionals are critical to the successful application of linear-scaling density functional theory (DFT). Local and semi-local functionals of the density are naturally compatible with linear-scaling approaches, having a general form which assumes the locality of electronic interactions and which can be efficiently evaluated by numerical quadrature. Presently, the most sophisticated and flexible semi-local functionals are members of the meta-generalized-gradient approximation (meta-GGA) family, and depend upon the kinetic energy density, τ, in addition to the charge density and its gradient. In order to extend the theoretical and computational advantages of τ-dependent meta-GGA functionals to large-scale DFT calculations on thousands of atoms, we have implemented support for τ-dependent meta-GGA functionals in the ONETEP program. In this paper we lay out the theoretical innovations necessary to implement τ-dependent meta-GGA functionals within ONETEP's linear-scaling formalism. We present expressions for the gradient of the τ-dependent exchange-correlation energy, necessary for direct energy minimization. We also derive the forms of the τ-dependent exchange-correlation potential and kinetic energy density in terms of the strictly localized, self-consistently optimized orbitals used by ONETEP. To validate the numerical accuracy of our self-consistent meta-GGA implementation, we performed calculations using the B97M-V and PKZB meta-GGAs on a variety of small molecules. Using only a minimal basis set of self-consistently optimized local orbitals, we obtain energies in excellent agreement with large basis set calculations performed using other codes. Finally, to establish the linear-scaling computational cost and applicability of our approach to large-scale calculations, we present the outcome of self-consistent meta-GGA calculations on amyloid fibrils of increasing size, up to tens of thousands of atoms. [ABSTRACT FROM AUTHOR]

Double-hybrid density functional approximations (DH-DFAs) provide an accurate description of the electronic structure of molecules by semiempirically mixing density functional and wavefunction theory. In this paper, we investigate the properties of the potential used in such approximations. By using the optimized effective potential approach, the consistent Kohn-Sham (KS) potential for a double-hybrid functional (including the second-order perturbational contribution) can be generated. This potential is shown to provide an improved description of orbital energies as vertical ionization potentials (IPs), relative to the perturbation-free KS potential typically used. Based on this observation, we suggest that DH-DFAs should be constructed in such a way that the potential provides accurate orbital energies. As a proof of principle, the B2-PLYP functional is reparameterized to obtain the IP-optimized B2IP-PLYP functional, using a small set of vertical IPs and atomization energies as reference data. This functional is shown to outperform B2-PLYP in a wide range of benchmarks and is en par with the related B2GP-PLYP. In particular, it is shown to be the most reliable choice in electronically difficult and multireference cases. [ABSTRACT FROM AUTHOR]

As a consequence of its high atomic number density, diamond can incorporate a relatively limited range of impurities as distributed point-defects, chiefly N, B and H. A few other species can be grown-in, and other impurity species incorporated via implantation and annealing. For applications including electronic, electrical and quantum devices, the presence of states deep within the wide band-gap is of importance, and the list of potential colour centres available for exploitation continues to grow. Although B can be grown into diamond at high concentration, study of other group-13 elements is rather limited. In this paper we present the results of modelling of Al, Ga and In. We find all species readily form complexes with vacancies, and exhibit electronic structures that parallel those of the Si V complex. We report electronic structures, electrical levels, optical transitions and hyperfine interactions of the colour centres, as well as reflect upon the thermodynamics of the complexes. We suggest that co-implanting group-13 elements with nitrogen would give rise to the defect charge states with potential for quantum applications. [Display omitted] • Group-13 impurities, Al, Ga and In, form viable colour centres in diamond for quantum-based technology when co-doped with N • Colour centres may either involve a vacancy or a complex with both a vacancy and nitrogen • Predictions of observables of substitutional Al, Ga and In, their complexes with vacancies and nitrogen are reported • Implanted impurities are not expected to be observed as interstitials after annealing [ABSTRACT FROM AUTHOR]

• BN nanocages were constructed for synergistically curvature-polarity regulation. • Curved BN nanocages provide chemical anchoring sites for the HCHO molecules. • A multi-channel electron balance transfer mechanism formed in curved BN surface. • Curved BN nanocages present dual-catalytic sites to accelerate HCHO oxidation. Development of efficient catalysts for formaldehyde (HCHO) oxidation is of importance in indoor air pollution treatment. However, the robust design criteria remain greatly challenging because of the poor recognization of structure-function relationships. Herein, by means of density functional theory (DFT) calculations, we proposed a surface modulation strategy to optimize the surface polar bonding state of BN, proving a curvature tuned B–N–B active sites and its relationship with catalytic activity. The results indicated that HCHO can be efficiently adsorbed by the curved BN nanocage with exceptional chemisorption efficiency (up to 97 %) and even under high coverage (two molecules, 86 %). Moreover, the distortion of BN nanocage facilitates the electron transfer from electron-rich O atom of HCHO to B 2p orbital, and then transfer to O 2 via the B–N polar bond, leading to the implementation of HCHO chemisorption and O 2 activation. Thus, a multi-channel for interactive electron transfer was spatially built for the HCHO oxidation on BN nanocage. Finally, a novel BN nanocage initiated advanced HCHO oxidation mechanism, combining the curvature and polarity catalytic effects, is systematically investigated based on reaction-kinetic studies. These findings shed new light on the rational design of HCHO oxidation catalysts and broadened the applications of BN-based materials. In this paper, a strategy of "synergistically curvature and polarity bond regulation" is reported to effectively modulate the electronic structure of BN surface sites to form a multi-channel electron balance transfer mechanism between HCHO/O 2 and catalyst. Benefiting from the curvature-enhanced polarization effect, the curved BN catalyst displays excellent adsorption and catalytic oxidation performance for HCHO. [Display omitted] [ABSTRACT FROM AUTHOR]