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Context and results : In this paper, the crystal structure, electronic, optical, and mechanical properties of SrVO3 have been systematically studied by first-principles calculation. The results show that the calculated lattice parameters are in good agreement with the experimental values of X-ray diffraction. The density of states is described in detail in this paper. By analyzing the crystal structure and electronic properties of SrVO3, the magnetic properties of SrVO3 are obtained from the one unpaired electrons of V and the exchange interaction between two V ions. At the same time, a detailed analysis of the optical properties of SrVO3 was conducted, and it was found that it is transparent in the visible light range. Finally, the mechanical properties of SrVO3 are calculated, which can provide some references for future research. Computational method: In this paper, a first-principles method based on density functional theory (DFT) is reported for PBE-GGA analysis using the plane wave-pseudo potential method in a quantum concentrate packet, U value of 7 eV to V-d and a U value of 2 eV to O-p, Grimme correction by DFT-D method. The k points in the Brillouin region are set to 4 × 4 × 4. The energy convergence criterion for self-consistent field calculation is set at 5.0 × 10−6 eV/atom, and the cutoff energy is 1170 eV. In this paper, the force acting on each atom is not more than 0.01 eV/Å, the maximum stress is not more than 0.02GPa, and the maximum atomic displacement is 5 × 10−4 Å. [ABSTRACT FROM AUTHOR]

Context and results : In this paper, the crystal structure, electronic, optical, and mechanical properties of SrVO3 have been systematically studied by first-principles calculation. The results show that the calculated lattice parameters are in good agreement with the experimental values of X-ray diffraction. The density of states is described in detail in this paper. By analyzing the crystal structure and electronic properties of SrVO3, the magnetic properties of SrVO3 are obtained from the one unpaired electrons of V and the exchange interaction between two V ions. At the same time, a detailed analysis of the optical properties of SrVO3 was conducted, and it was found that it is transparent in the visible light range. Finally, the mechanical properties of SrVO3 are calculated, which can provide some references for future research. Computational method: In this paper, a first-principles method based on density functional theory (DFT) is reported for PBE-GGA analysis using the plane wave-pseudo potential method in a quantum concentrate packet, U value of 7 eV to V-d and a U value of 2 eV to O-p, Grimme correction by DFT-D method. The k points in the Brillouin region are set to 4 × 4 × 4. The energy convergence criterion for self-consistent field calculation is set at 5.0 × 10−6 eV/atom, and the cutoff energy is 1170 eV. In this paper, the force acting on each atom is not more than 0.01 eV/Å, the maximum stress is not more than 0.02GPa, and the maximum atomic displacement is 5 × 10−4 Å. [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]

In this paper, the electronic structures of rare earth (Nd, Er)-doped MgO were investigated using density functional theory (DFT), with Hubbard on-site corrections (Ueff) applied to rare earth elements. Li was considered a co-dopant. Defect complexes were involved, instead of a single dopant atom, in the supercell. The splitting and distribution of the 4f ground states of Nd and Er dopants in the band gap changed by co-doping Li. The calculation results provide insights into the influences of Li on the optical properties of rare-earth-doped MgO. [ABSTRACT FROM AUTHOR]

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]

In this paper, we studied the magnetic stability, structural, elastic and electronic properties of Ir2FeAl full Heusler compound in the regular phase (Cu2MnAl, prototype L2 1) , by using the first principle of density functional theory, with the generalized approximation of the GGA gradient. We found that the ferromagnetic state of Ir2FeAl is more stable than the nonmagnetic configuration at their lattice parameters equilibrium. This result was confirmed by the calculation of the cohesive energy. The stability is asserted by the elastic constants and the conditions of the mechanical stability criterion. The band structure and the calculated densities of states (DOS) of this alloy show a semi-metallic behavior. The ferromagnetic performance of Ir2FeAl is confirmed by the total magnetic moment of 4.28 μ B , where its major contribution comes from Fe atoms. We estimated the Debye temperature of Ir2FeAl from the average speed of sound. This is the first quantitative theoretical prediction of the elastic properties of the Ir2FeAl compound, and it still awaits experimental confirmation. [ABSTRACT FROM AUTHOR]

The complex theoretical analysis of the density of states, band structures, and Fermi surfaces, based on predictions of the density functional theory methods, unveils the unique electronic properties of the LaZn1−xBi2 system. In this paper, the Zn vacancies (for x = 0.5 ) were modeled using a modified unit cell of lower symmetry than that for a fully stoichiometric one (for x = 0 ). The existence of several Dirac-like features in the electronic band structures was found. Some of them were found to be intimately associated with the nonsymmorphic symmetry of the system, and these were investigated in detail. The calculated Fermi surface shapes, as well as the Fermi velocity values (up to ∼1.2 × 10 6 m/s), are in good agreement with other analogous square-net Dirac semimetals. The combination of charge-carrier uncompensation, relatively small band splitting, and the tolerance factor for square-net semimetals t ≤ 0.95 for LaZn0.5Bi2, constitutes a very promising indicator of the topological features of this system, warranting further experimental studies. [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]

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]

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]

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 electronic and spin structures of the [8Fe–7S] inorganic model complex (1) have been investigated using the density functional theory (DFT) UB3LYP and UBLYP methods. The experimental geometry of 1 was used to calculate the sets of exchange interactions (J values) between Fe-spin centers within spin Hamiltonian models. The experimental temperature-dependent paramagnetism is well reproduced on the basis of the calculated J values. The calculated low-lying energy levels are also consistent with those of the experiments. This indicates that the ground spin state of 1 is singlet (S = 0) for the weak antiferromagnetic coupling between two [4Fe–3S] cubane units, which take the Fe(III)Fe(II)3 formal charge and S = 7/2 spin states. The first-order density matrix of the most stable broken-symmetry (BS) solution has been diagonalized to elucidate the natural molecular orbitals (MOs) and their occupation number of 1, which are hardly obtained by the symmetry-adapted (SA) CASSCF approach. Several chemical indices such as the effective bond orders before and after spin projection are also calculated by using the occupation numbers to provide the SA MO picture of labile chemical bonds of 1. It is found that the BS MO calculation followed by spin-projected SA analysis is an effective and practical alternative to the CASSCF MO approach for the multinuclear transition metal clusters. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [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]

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]

The catalytic efficiency of CeO2 in soot oxidation was significantly affected by its grain morphology and calcination temperature. Nanocube-shaped and nanorod-shaped CeO2 catalysts were synthesized via a hydrothermal method with different calcination temperatures. Activity tests revealed that the nanorod-shaped CeO2 exhibited superior catalytic activity compared to the nanocube-shaped catalysts at equivalent calcination temperatures. Furthermore, an inverse relationship between the catalytic activity and the calcination temperature was observed in the nanorod-shaped CeO2 catalysts, with those calcined at 300 °C exhibiting the most effective low-temperature catalytic performance. Combined characterization techniques and density functional theory calculations showed that the improved catalytic performance can be attributed to the increased abundance of oxygen vacancies, enhanced lattice oxygen mobility and higher surface energy due to their unique surface defect structure and electronic structural feature, in addition to the reduction in grain size. [ABSTRACT FROM AUTHOR]

van der Waals (vdWs) interchain coupling is a unique feature of 1D vdWs materials, where strong vdWs coupling in 1D vdWs materials leads to the thickness‐dependent physical properties, while weak vdWs coupling can preserve the single‐chain property even in their thick counterparts. Different from 2D vdWs materials, due to their nanoscale widths, identifying and producing ultrathin 1D molecular chains are challenging, severely limit their device applications. Thus, looking for novel 1D vdWs materials with weak interchain coupling is crucial. In this paper, the authors report that the 1D ternary vdWs material, Mo6Se2I8 with non‐centrosymmetric characteristic and strong optical anisotropy, exhibits weak interchain coupling. On one hand, the density functional theory (DFT) calculations theoretically demonstrate its thickness‐independent electronic structure, negligible interchain differential charge density, and weak cleavage energy as low as 0.256 J m−2. On the other hand, the thickness‐independent work function and low first‐order temperature coefficient of −0.0030 cm−1 K−1 further experimentally confirm its weak interchain coupling. Moreover, taking advantage of this weak vdWs coupling characteristic, the in situ exfoliation of the Mo6Se2I8 nanowires is achieved by using a nanoprobe in a scanning electron microscope (SEM), obtaining ultrathin molecular chains with a thickness of ≈1.2 nm. [ABSTRACT FROM AUTHOR]

Density functional theory calculations have been performed to compare the HCHO decomposition on Co3O4(110)-A and (110)-B terminations. The results showed that the energy barriers of the two C–H bond cleavages of HCHO on the (110)-A termination were lower than those on the (110)-B termination, suggesting that the (110)-A termination had stronger HCHO decomposition ability than the (110)-B termination. Electronic structures revealed that the stronger HCHO decomposition ability of the (110)-A termination might be ascribed to the strong covalent bond between HCHO and the (110)-A termination, as well as the higher d-band center of Co3+ ions on the (110)-A termination. Furthermore, we proposed that the preparation of Co3O4 under oxygen-rich growth conditions was beneficial to HCHO decomposition because the (110)-A termination was more stable under oxygen-rich conditions. [ABSTRACT FROM AUTHOR]

The energy difference between different spin states of systems with transition metals is an outstanding challenge for electronic structure calculation methods. The small energy difference between high- and low-spin states in spin-crossover systems makes most post-Hartree–Fock or density functional theory-based methods provide inaccurate values. A test case of twenty systems showing spin transitions has been used to evaluate the accuracy of a new family of training meta-GGA (Generalized Gradient Approximation) functionals. One of the functionals of this new family provides comparable or even better values than the best functional reported so far for this type of system, the TPSSh hybrid meta-GGA functional, but without having to use the exact exchange term. It also improves the results obtained with the r2SCAN meta-GGA functional, which was the best alternative to the TPSSh hybrid functional. This makes it possible to calculate the spin energetics of any kind of compound, especially large systems or periodic structures where the exact exchange requires large computational resources. [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]

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]

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]

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]

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]

In this study, metal-doped niobates and perovskites were obtained by a solid-state reaction. The solids were evaluated in the esterification of glycerol in the presence of acetic acid to produce valuable esters of glycerol. The structural features of the solids indicated the ZnNb2O6, Pb2.8Nb2O7.8 and CuNb2O6 columbite main phases and La2MnFeO6 double-perovskite. Density functional theory (DFT) studies of Pb2.8Nb2O7.8 clearly confirmed the existence of a robust orthorhombic structure and its electronic properties were correlated with the Nb and Pb interactions. The morphological and elemental analyses also indicated that not all surface elements, as well as morphology, were crucial for catalytic properties. All solids were active and selective toward triacetin formation upon glycerol esterification with acetic acid. The catalytic performance depends mainly on the availability of the surface and its structural stability, as well as defects formation. Recyclability studies indicated that the La2MnFeO6 double-perovskite was an efficient catalyst, achieving glycerol conversion of 68% and triacetin selectivity of 25% up to 4 cycles of use in the reaction. The structural defects near the Mn4+/Mn3+ surface sites resulted in the diffusion of anions and an increased concentration of oxygen vacancies contributed to the stable performance of the solid in glycerol ester production. [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: 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]

In this work, density-functional theory (DFT) was used to investigate the geometry and electronic structure of Run(n = 1–6,10) supported on CeO2(110) (Run(n = 1–6,10)/CeO2(110)) and their electrocatalytic properties for the N2 reduction reaction (NRR). The results indicated that there is a strong metal–support interaction between Run and CeO2(110), which leads to large surface distortion and stabilized Run. On Run(n = 1–6,10)/CeO2(110), N2 captured in the end-on mode is thermodynamically more favorable than that captured in the side-on mode; however, the side-on mode can lead to stronger activation of N2 which promotes the following protonation step of N2. For Run(n = 3,5,6)/CeO2(110), the electrochemical NRR prefers to occur via an enzymatic mechanism with limiting potentials of −0.31, −0.53 and −0.66 V. The electrocatalytic activity of Run(n = 1–6,10)/CeO2(110) for the NRR shows a strong size dependence. For Ru3/CeO2(110), it has the lowest absolute value of limiting potential, and with the increase in n (n > 3), the limiting potential becomes more negative. Moreover, Ru3/CeO2(110) shows high selectivity and stability. This study gives valuable insights for designing effective catalysts for the NRR. [ABSTRACT FROM AUTHOR]

Douglas Hartree and Hilleth Thomas were graduate students together at Cambridge University in the mid-1920s. Each developed an important approximation method to calculate the electronic structure of atoms. Each went on to make significant contributions to numerical analysis and to the development of scientific computing. Their early efforts were fused in the mid-1960s with the development of an approach to the many-particle problem in quantum mechanics called density functional theory. This paper discusses the experiences which led Hartree and Thomas to their approximations, outlines the similarities in their subsequent careers, and highlights the essential role their work played in the foundational papers of modern density functional theory. [ABSTRACT FROM AUTHOR]

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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]