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Context: The effect of X (X = O, Se, N, P, F, Cl) doping on the adsorption of Zn atoms by WS2 was investigated based on first principles. The electronic structure and optical properties of the adsorbed system after atomic doping were calculated. It is found that the Zn atom adsorbed on the W top (Tw) site has the most stable structure. When an S atom is replaced with an X atom based on the adsorption system, where the adsorption energy decreases after doping of O, P, F, and Cl atoms compared to the undoped system, it means that each system is more stable after doping of these atoms; charge transfer shows that the adsorption system after P-atom doping the system around the Zn atom loses electrons while S-atom gains electrons, which indicates that P-atom doping is favorable for the adsorption of Zn by WS2, N, P-atom is introduced as p-type doping and F, Cl-atom is introduced undoped by n-type doping, and the band gap of the doped system is less than that of the undoped one. With the introduction of different dopant atoms, certain impurity energy levels are introduced into the adsorption system. The prohibited bandwidth around the Fermi energy level reduces the density of states, causing the doped system's density of states to shift to lower energies, among which the shifts of N, P, F, and Cl are more pronounced. The P-doped adsorption system shows a new peak near the energy of − 11 eV. In addition, the study of optical properties showed that the peak reflections of both doped and non-doped systems adsorbing Zn atoms appeared in the ultraviolet region; the absorbance coefficient of the doped system is moved in the lower energy direction and red-shifted after atom doping; in addition, the absorption coefficients and reflectance of the P, Se doped systems are enhanced in the wavelength range of 200–300 nm compared with that before doping, the dielectric function and CBM and VBM positions were also calculated further indicating the potential of Se-doped systems in improving photocatalytic efficiency. Methods: In this paper, the structure optimization of X (X = O, Se, N, P, F, Cl) doping on WS2 adsorbed Zn atom model is performed based on the CASTEP module in Materials-Studio software under the first principles using GGA and PBE generalized function. The corresponding binding energies, bond lengths, bond angles, charge densities, energy band structures, densities of states, and optical properties were also analyzed. The Monkhorst–Pack particular K-point sampling method is used in the calculations; the K-point grid is 6 × 6 × 1, and the cutoff energy for the plane wave expansion is 500 eV. After geometric optimization, the iterative accuracy converges to a value of less than 1 × 10−5 eV/atom for the total energy of each atom and less than 0.03 eV/Å for all atomic forces. The thickness of the vacuum layer was set to 20 Å to avoid the effect of interlayer interaction forces. In this paper, 27 atoms were used to form a 3 × 3 × 1 supercellular tungsten disulfide system consisting of 18 S atoms and 9 W atoms. [ABSTRACT FROM AUTHOR]

In the field of research on renewable energy conversion and storage methods, the development of catalysts with excellent properties and outstanding stability for oxygen evolution reaction (OER) acting at various pH values has become a much-anticipated research focus. RuO 2 as a benchmark OER catalyst, its wide application has always been limited by slow reaction kinetics and limited persistence. In this paper, Mn-doped RuO 2 material was developed and the optimum doping ratio was identified for using as an OER electrocatalyst under general purpose pH media. Mn 0.1 Ru 0.9 O 2 exhibited a lower overpotential value of 224 mV in acidic environment with a Tafel slope value of 51.62 mV dec−1. Moreover, in alkaline and neutral environments, overpotentials of 231 mV and 376 mV were required to obtain a current density of 10 mA cm−2, respectively. In addition, through continuous stability testing over 24 h in alkaline, acidic and neutral solutions, it has been further demonstrated that the Mn-doped RuO 2 material exhibits extremely high stability. The advancements in this research offer crucial insight into the rational development of efficient and durable RuO 2 -based catalysts. [Display omitted] • Mn 0.1 Ru 0.9 O 2 is successfully synthesized by a facile sol-gel method. • Mn doping modulates the electronic structure of RuO 2. • The catalyst exhibits enhanced OER activity and stability in pH-Universal media. [ABSTRACT FROM AUTHOR]

Dilute magnetic semiconductors (DMSs) with both charge and spin degrees of freedom have emerged as promising candidates in the spintronic industry. However, the Curie temperature below room temperature and uncertainty about the origin of ferromagnetism hinder the application of DMSs. To address these issues, we explored a better SnO2-based co-doped method (Fe, V + VSn) using ab initio calculations. The calculation results show that the Sn13FeVO32 (Fe, V + VSn) has a high Curie temperature (716 K), good ferromagnetic properties, stronger covalency of bonds, and better optical transparency in the visible light range. In addition, the holes or electrons generated by the complexes in the (Fe, V + VO/VSn) co-doped system cause a spin-polarized double exchange effect in the Fe-3d, V-3d, and O-2p orbitals, which leads to magnetism of the co-doped systems. The static dielectric constant ɛ1(0) of the system increases after doping. Among them, Sn14FeVO31 (Fe, V + VO) has the largest ɛ1(0), indicating that Sn14FeVO31 has the strongest polarization ability and better photocatalytic properties. In Sn14FeVO31, the imaginary part of the dielectric function and the absorption spectrum all have new peaks in the low-energy region, which are caused by the jump of electrons from the guide band of the spin-polarized impurity energy level. This paper proposes a new method for preparing dilute magnetic semiconductors in spin electronic devices with high room temperature ferromagnetic properties and excellent optical properties through the (Fe, V + VO/VSn) co-doped SnO2. [ABSTRACT FROM AUTHOR]

Facile synthesis of FeNi alloy-supported N -doped Mo 2 C hollow nanospheres for enhanced oxygen evolution reaction. [Display omitted] • Facile synthesis of FeNi alloy-supported N -doped Mo 2 C hollow nanospheres. • FeNi/Mo 2 C/NC supports strongly accelerated electron transfer, thereby improving the OER kinetics. • FeNi/Mo 2 C/NC hybrids will hold promise in development of electrode materials. The rapid depletion of fossil fuels results in significant environmental pollution. Consequently, researching environmentally friendly and cost-effective electrocatalysts with exceptional oxygen evolution reaction (OER) capabilities holds immense importance in enhancing the efficient utilization of resources. In this paper, a straightforward and cost-effective method was employed to produce Fe-Ni alloy-supported N -doped carbon hollow nanospheres (FeNi/Mo 2 C/NC) using self-assembled molybdenum dopamine spheres (Mo-PDA-HS) as a substrate. The inclusion of iron and nickel addressed the issue of aggregation and collapse in Mo-PDA-HS nanostructures at high temperatures, while adjusting the electronic structure of the composites to achieve efficient OER activity. The composite displayed a low overpotential (η10 mA = 304 mV) and a minimal Tafel slope (41.8 mV/dec-1). This study introduces a simple strategy for constructing structurally robust and non-aggregating Mo 2 C nanostructures, along with a direct method for designing cost-effective and high-performance catalysts for OER. [ABSTRACT FROM AUTHOR]

This paper reports the energies and charge and spin distributions of the mono-substituted N defects, N0s, N+s, N−s and Ns-H in diamonds from direct Δ-SCF calculations based on Gaussian orbitals within the B3LYP function. These predict that (i) Ns0, Ns+ and Ns− all absorb in the region of the strong optical absorption at 270 nm (4.59 eV) reported by Khan et al., with the individual contributions dependent on the experimental conditions; (ii) Ns-H, or some other impurity, is responsible for the weak optical peak at 360 nm (3.44 eV); and that Ns+ is the source of the 520 nm (2.38 eV) absorption. All excitations below the absorption edge of the diamond host are predicted to be excitonic, with substantial re-distributions of charge and spin. The present calculations support the suggestion by Jones et al. that Ns+ contributes to, and in the absence of Ns0 is responsible for, the 4.59 eV optical absorption in N-doped diamonds. The semi-conductivity of the N-doped diamond is predicted to rise from a spin-flip thermal excitation of a CN hybrid orbital of the donor band resulting from multiple in-elastic phonon scattering. Calculations of the self-trapped exciton in the vicinity of Ns0 indicate that it is essentially a local defect consisting of an N and four nn C atoms, and that beyond these the host lattice is essential a pristine diamond as predicted by Ferrari et al. from the calculated EPR hyperfine constants. [ABSTRACT FROM AUTHOR]

• A high-performance Pd-Ni/NPCs catalyst for directly synthesizing hydrogen peroxide was easily prepared using a simple chemical displacement method. • Ni modification regulates the electronic structure of Pd through electron transfer and compressive stress, leading to electron enrichment in Pd and lowering the d -band center of Pd. • Ni modulates the electronic structure of Pd, reducing the hydrogenation activation energies of O 2 * and OOH* and increasing the dissociation activation energies of O 2 *, OOH*, and HOOH*, which improves the selectivity and productivity of H 2 O 2. • Crystal Orbital Hamilton Population (COHP) analysis shows a correlation between energy-integrated COHP (ICOHP) of O O bonds in reaction intermediates and activation energies, providing insights into the catalyst's surface reaction mechanism. • Synthesized Pd-Ni/NPCs catalysts based on theoretical predictions demonstrate excellent H 2 O 2 selectivity and productivity, validating the effectiveness of the proposed catalyst design strategy. Developing high-performance catalysts for direct synthesis of hydrogen peroxide (H 2 O 2 ; DSHP) remains challenging. The paper proposes a strategy to optimize Pd catalysts by enriching Ni-modified N-doped porous carbon. The theoretical studies indicate that Ni modulates the electronic structure of Pd through charge transfer and strain effects, effectively reducing the adsorption energy of reaction intermediates. Furthermore, the Crystal Orbital Hamilton Population (COHP) analysis demonstrated that the energy-integrated COHP (ICOHP) of the O O bonds in O 2 * (* denotes the adsorbed state), OOH*, and HOOH* were positively correlated with dissociation activation energies and negatively correlated with hydrogenation activation energies. The modulation of the electronic structure of Pd by Ni reduces the hydrogenation activation energies of O 2 * and OOH* and increases the dissociation activation energies of O 2 *, OOH*, and HOOH*, thereby enhancing the selectivity and productivity of H 2 O 2. The experimental results aligned with the theoretical predictions, showcasing that the optimized Pd-Ni 7.5 /NPCs catalyst exhibited remarkable H 2 O 2 selectivity and productivity of 70.5 % and 230.31 mol kg cat -1·h-1, respectively, surpassing the performance of Pd/NPCs (47.1 % and 52.3 mol kg cat -1·h-1). This study offers profound insights into the crucial role of electron effects in DSHP using nickel-modified palladium catalysts, providing strong evidence into the design and optimization of Pd catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

Reduction in the dimensions of silicon based devices has produced extraordinary developments in the performance of electronic systems. Recently, the advantages and challenges that caused by silicon devices shrinking have been investigated in many studies. Most of them have concluded that silicon technology is coming to an end and new innovations are required in the near future. Graphene is the promising candidate material as building blocks for nanoelectronic industry in order to silicon technology replacement. Graphene is first two dimensional materials that has significant potential in future nanoelectronic devices and other nanotechnology applications; therefore, it is an attractive subject for the researchers and scientists. Graphene is a carbon allotrope and is the basic element of other carbon allotropes. In this paper, main graphene production approaches are mentioned. The mechanical, thermal, optical, electrical, electronic and other fundamental properties of graphene are introduced. Moreover, it is considered as a novel material with numerous applications, which, we mention a few of important utilizations of graphene and its derivatives. Then, the different types of defects in graphene and their specifications, the methods of defect generation, defect healing, and properties of defective graphene are studied. Graphene nanoribbons and their geometric structures, fabrication approaches and electronic specifications are investigated. The effects of width, vacancy defect and doping concentration on the band structure of the graphene nanoribbons are extracted with ATK software in this paper. Simulation results showed that by increasing in the width, vacancy defect and doping concentration of nanoribbons, their band gap were decreased. These properties are suitable for controlling the channel of graphene nanoribbon field effect transistors. [ABSTRACT FROM AUTHOR]

Abstract In this paper, four types of compounds are considered: ideal wurtzite (B N), N vacancies in B N (B N − V N), A l doped ideal B N (A l : B N) and A l doped B N with N vacancies(A l : B N − V N). The structural, electronic and magnetic properties are calculated by using the density functional theory (DFT) based on the generalized gradient approximation implemented in Quantum-Espresso code. Our results show that the nitrogen vacancies and the aliminium impurities are responsible of the magnetic properties in these compounds. We have also found that aluminium impurities have a remarkable effect on the optical band gap. Our results are in good agreement with experimental and other theoretical studies. We can conclude from this study, that this material can be used as diluted magnetic semiconductors. Highlights • The DFT method has been used to study the Al doped (w−BN). • The lattice parameters increase with the incorporation of Al in the BN supercell. • The Al impurities decrease the value of the band gap. • Al and N vacancy induce magnetic properties. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Structural, magnetic and optical properties of Mg-doped CeO 2 (1 1 1) surface were investigated. • The doped CeO 2 (1 1 1) surface systems exhibit different bonding character. • The doped surface and subsurface systems result in local and scattered spin atmosphere. • The incorporation of Mg can lead to the red shift of absorption edge. Abstract The electronic structure, magnetic and optical properties of Mg-doped CeO 2 (1 1 1) surface have been investigated by first-principles calculations. In this paper, the doping case is actively favorable to process under O-rich conditions than under Ce-rich conditions. The distortion of doping systems of Mg replacing Ce of surface is larger than that of subsurface. The covalent character is getting weaker and the ionic character is gradually obvious for Mg O bond from surface to subsurface doping. The results show that the existence of defect states with O 2 p orbital character makes spin splitting, causing the local and scattered magnetic moments for surface and subsurface doping of Ce, respectively. And the 9 and 12 atomic layers doping systems exhibit magnetic ground states with different magnetic moments. In particular, the calculated Curie temperature (about 434, 483, 1200 K) is higher than room temperature (RT), therefore, the theoretical results showed that Mg-doped CeO 2 (1 1 1) thin films would can be obtained stable room temperature ferromagnetism (RTFM), which is beneficial to practical application. In addition, the optical properties show that all doped systems are capable of enhancing effective absorption of visible and near-infrared light. [ABSTRACT FROM AUTHOR]

The study of the optical properties of pristine BNNT, Si-doped BNNTs and SO 2 molecule adsorption on Si-doped BNNTs is that, to our knowledge, few relevant research have ever been found. In this paper, the adsorption behaviors of Sulfur dioxide (SO 2 ) molecule on Si-doped Boron nitride nanotubes (BNNTs) are investigated applying the first-principles calculations. The main contribution of this paper is that the foremost investigation for the optical properties of the pristine BNNT, Si-doped BNNTs and SO 2 adsorption on Si-doped BNNTs. Additionally, the electronic properties and the structural properties are also presented. In our calculations of optical properties, the dielectric constant, the refractive index and the absorption coefficient are obtained. Comparing the pristine BNNT, our results indicate that, the blue-shifts (in the main peaks of the dielectric constant of Si B - BNNT and SO 2 - Si B - BNNT ), and the red-shifts (in the main peaks of the refractive index of Si N - BNNT and SO 2 - Si N - BNNT ) are appeared. Under these conditions, Si-doped BNNT and Si-doped BNNT with SO 2 adsorption, the gaps are reduced both for the speculated optical band gaps and the electronic structure band gaps. [ABSTRACT FROM AUTHOR]

In this paper, the structural, electronic and magnetic properties of small Fe m V n (m+n ≤ 6) clusters have been investigated systematically within the framework of the generalized gradient approximation density-functional theory. The results indicate that the low lying isomers of Fe m V n alloy clusters all present the classical closely packed geometries with different chemical order when m + n > 4; the ground state structures prefer to form the Fe–V as much as possible in small proportion V doping. The binding energy of Fe m V n clusters always increases with the successive V substitution. The V atom mono-doped and bi-doped make the magnetism of Fe n clusters decrease 7  μ B , respectively. With V atom doping increasing, the magnetism presents an overall decreased tendency. The magnetic order bewteen Fe and V atoms undergoes a transition from antiferromagnetic coupling in Fe-rich clusters to the coexistence of antiferromagnetic and ferromagnetic couplings in V-rich clusters, and the atom net charge usually transfer from V to Fe atom in Fe m V n alloy clusters. [ABSTRACT FROM AUTHOR]

The structural, elastic properties, hardness and electronic structure of Mo 2 FeB 2 alloyed with Cr and Ni have been investigated by using first-principles calculations. The doping concentrations of 2.5 at. %, 5.0 at. %, 10.0 at. % and 20.0 at. % are analyzed systematically in this paper. From the calculated impurity formation energy, it is found that all the structures can retain good structural stability with the doping concentrations of Cr, Ni up to 20.0 at. %. According to the calculated elastic constants, it is observed that Cr can increase the Young’s modulus and hardness and reduce the ductility of Mo 2 FeB 2 markedly with the increasing of alloying concentration. In contrast, Ni can decrease the hardness but improve the ductility of Mo 2 FeB 2 obviously. The calculated electronic structure indicates that the increase of elastic modulus is attributed to the formation of B Cr bond for Cr-doped and B Ni bond for Ni-doped. The Mo Cr and Mo Ni metallic bonds weaken the shear modulus of Mo 2 FeB 2 . When the doping concentration is 20.0 at. %, it is obvious that the alloying elements Cr and Ni can significantly affect the moduli of Mo 2 FeB 2 . [ABSTRACT FROM AUTHOR]

Narrow bandgap and its tuning are important aspects of materials for their technological applications. In this context group IV{VI semiconductors are one of the interesting candidates. In this paper, we explore the possibility of bandgap tuning in one of the family member of this family GeSe by using isoelectronic Pb doping. Our study is first-principles based electronic structure calculations of Ge1-xPbxSe. This study reveals that the Ge-p and Se-p states are strongly hybridized in GeSe and shows a gap in the DOS at Ef in GeSe. This gap reduces systematically with simultaneous enhancement of the states in the near Ef region as a function of Pb doping. This leads tuning of the indirect bandgap in GeSe via Pb doping. The results of the indirect bandgap decrement are consistent with the experimental findings. We propose a mechanism where the electrostatic effect of dopant Pb cation could be responsible for these changes in the electronic structure of GeSe. [ABSTRACT FROM AUTHOR]

This paper described a comprehensive DFT + U investigation on the general trends in structural stability, electronic and optical absorption properties, photocatalytic activity of BiOCl doped with 3 d transition metals (TMs = Sc, V, Cr, Ti, Fe, Co, Ni, Cu, Zn). We find that it is rather difficult for Sc, V, Ti, Ni atoms to substitute Bi into BiOCl crystal lattice in experiments due to their positive formation energies, but the negative formation energies for Cr-, Mn-, Fe-, Co-, Ni-, Cu-, Zn-doped BiOCl systems exhibit the thermodynamic structure stability. Most of TMs doping could narrow the band gap of BiOCl and lead to the changes in conduction band minimum and valance band maximum as well as the formation of several impurity energy levels within the forbidden band of BiOCl, achieving the photoactivity improvement and simultaneously maintaining the stronger redox potential. With 3 d TMs doping, the optical absorption intensity of BiOCl around 350 nm increased and exhibited a redshift to the different extents, in good agreement with reported experimental data. Our theoretical calculations should provide meaningful guidance for the experimentalists to design and develop more thermodynamically stable and highly effective visible light response photocatalysts. [ABSTRACT FROM AUTHOR]

In the paper, the electronic properties and magnetic orderings in the Mn/Gd doped zinc-blende (ZB) and wurtzite (WZ) structural CdSe are investigated extensively using first-principles calculations. We find that the infiltration of Mn ions in the ZB/WZ structural CdSe will lead to the antiferromagnetic ordering; while the infiltration of Gd ions will lead to the ferromagnetic ordering. Moreover, the antiferromagnetic/ferromagnetic coupling interactions between the magnetic Mn/Gd ions will become more and more strong with decreasing Mn-Mn/Gd-Gd distance. Particularly, the electronic properties in the Mn mono-doping case (spin-polarized) and in the Mn double-doping case (ferromagnetic) are almost same, and they tend to be the magnetic/ferromagnetic semiconductor via the comparison from the different calculations; as a whole, the Mn doped ZB/WZ structural CdSe system tends to present the antiferromagnetic semiconductor character. In addition, the band gap in the Mn doped ZB/WZ structural CdSe decreases with increasing Mn concentration using GGA+U calculations. In contrast to the case of the Mn doped ZB/WZ CdSe: (i) the Gd doped ZB/WZ CdSe in the mono-doping case displays the magnetic semiconductor character; but the Gd doped ZB/WZ structural CdSe in the double-doping case presents the n-type ferromagnetic semiconductor, and the robust ferromagnetism is obtained in the system irregardless of the crystal structure and the distance between the magnetic ions; (ii) the band gap in the Gd doped ZB/WZ structural CdSe increases with increasing Gd concentration, Burstein-Mott-effect might be major reason. [ABSTRACT FROM AUTHOR]

The stable local minima due to the addition of the Li atom to the double-ring and the quasiplanar configurations of the B 24 molecule have been searched on the doublet potential energy surface to reveal the structural and electronic features of the Li@B 24 system. We report two and seven stable local minima without imaginary vibrational frequency for the Li@B 24 (double-ring) and the Li@B 24 (quasiplanar) systems, respectively. The criteria of the adsorption energy, the vertical ionization (VI) energy, the deformation energy, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy gap, the atomic charges, the spin density distribution, the electron transfer (ET), atoms in molecules (AIM) analysis and the nonlinear optical (NLO) properties have been investigated for all the reported molecules of the Li@B 24 system in the present paper. Our results present that both thermodynamic and chemical stability of the Li atom doping to the quasiplanar configuration of the B 24 molecule are more than those of the double-ring configuration. Additionally, both the double-ring and the quasiplanar configurations can produce the Li@B 24 system with values of high first hyperpolarizability (β total ) due to the Li atom doping. In all the reported molecules of the Li@B 24 system, electron density of the Li atom decreases due to the existence of the double-ring and the quasiplanar configurations confirming the role of the electron donor for the Li atom. In contrast, both decreasing and increasing electron density have been observed in the B atoms of the Li@B 24 system. However, the role of electron acceptor (increasing electron density) for the B atoms is more dominant than the role of electron donor (decreasing electron density). This result highlights chemical flexibility of the B atoms. [ABSTRACT FROM AUTHOR]

This paper illustrates the structural, electronic and optical properties of individual silicon (Si) atom-doped single layer graphene using density functional theory method. Si atom forms tight bonding with graphene layer. The effect of doping has been investigated by varying the concentration of Si atoms from 3.125% to 9.37% (i.e. From one to three Si atoms in 4 × 4 pure graphene supercell containing 32 carbon atoms), respectively. Electronic structure, partial density of states (PDOS) and optical properties of pure and Si atom-doped graphene sheet were calculated using VASP (Vienna ab-initio Simulation Package). The calculated results for pure graphene sheet were then compared with Si atom doped graphene. It is revealed that upon Si doping in graphene, a finite band gap appears at the high symmetric K -point, thereby making graphene a direct band gap semiconductor. Moreover, the band gap value is directly proportional to the concentration of impurity Si atoms present in graphene lattice. Upon analyzing the optical properties of Si atom-doped graphene structures, it is found that, there is significant change in the refractive index of the graphene after Si atom substitution in graphene. In addition, the overall absorption spectrum of graphene is decreased after Si atom doping. Although a significant red shift in absorption is found to occur towards visible range of radiation when Si atom is substituted in its lattice. The reflectivity of graphene improves in low energy region after Si atom substitution in graphene. These results can be useful for tuning the electronic structure and to manipulate the optical properties of graphene layer in the visible region. [ABSTRACT FROM AUTHOR]

The performance of TiO 2 nanosheets (TiO 2 -NSs) modified carbon paper anode (TiO 2 -NSs/CP) in S. loihica PV-4 inoculated MFCs is greatly improved by intentional N doping of TiO 2 -NSs to modulate its electronic properties. TiO 2 -NSs/CP is calcined in NH 3 atmosphere at different temperatures (T = 400, 500, 600 and 700 °C) to obtain N doped anodes (T-NTiO 2 -NSs/CP, T represents temperature), in which 600-NTiO 2 -NSs/CP electrode show best performance with the maximum output power density increased by 196% and 50% compared to that from the bare CP and TiO 2 -NSs/CP electrodes respectively. The surface morphology, structure and electrochemical activity are characterized by FESEM, XRD, Raman, XPS, CVs and EIS. The results show that heating in NH 3 atmosphere keep surface morphology and bio-affinity of the electrode. The midpoint potential E m (−0.29 V) of outer membrane c-type cytochromes (OMCs) at 600-NTiO 2 -NSs/CP anode is in accordance with that at TiO 2 -NSs/CP. However, 600-NTiO 2 -NSs/CP electrode had smaller charge transfer resistance, more positive flat-band potential and larger transient charge storage capacity than untreated electrode due to modulation of the electronic structure via N doping, which all are favorable to interfacial electron transfer from OMCs to underlying electrode. The method is simply and efficient, and could be extended to other nano-semiconductor modified electrodes for superior MFC anodes. [ABSTRACT FROM AUTHOR]

In this paper, the carbon-doped boron nitride nanoplate (C-BNNP) was prepared by pyrolyzing the precursor under N 2 and served as an excellent adsorbent for removal of Rhodamine B (RhB). The structure and composition of C-BNNP were characterized and its adsorption behavior for RhB was investigated. Compared with boron nitride nanoplate (BNNP) which was synthesized under NH 3 , C-BNNP displayed an enhancement of the adsorption capacity for RhB (833 mg/g). The adsorption activity was comprehensibly studied by kinetics, isotherm and thermodynamics. The adsorption kinetics followed pseudo-second-order model. The equilibrium adsorption data agreed well with the Langmuir isotherm. And the thermodynamics indicated that the adsorption process was a spontaneous, exothermic and physisorption process. In addition, the density functional theory was proposed that doping carbon in the BNNP decreased the chemical hardness of the adsorbent and enhanced the adsorption capacity of C-BNNP for RhB. [ABSTRACT FROM AUTHOR]

In this paper, structural and electronic properties and stability of (10, 0) born nitride nanotube (BNNT) are considered within density functional theory by doping group IV elements of the periodic table. The HOMO-LUMO gap has been strongly modified and treated a dual manner by choosing B or N sites for dopant atoms. Formation energy calculation shows that B site doping is more stable than N site doping. Results also show that all dopants turn the pristine BNNT into a p-type semiconductor except for carbon-doped BNNT at B site. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO 2 ) is an attractive transition metal oxide owing to its intriguing metal to insulator phase transition and has great potential for applications in smart windows. In this paper, first-principles calculations were conducted and the results revealed that Sb is as an efficient dopant in improving the thermochromic properties of VO 2 by lowering the phase transition temperature and enhancing the transmission of visible light, as well as increasing the near-IR absorption of VO 2 . These changes in the optical properties of VO 2 are closely correlated with the variations in the atomic and electronic structures, where the V V chains along the [0 0 1] direction present dimerization features in VO 2 (R) with Sb-doping; in addition, the O V bonds appear less ionic due to the O Sb ionic bonds. The calculation results are confirmed by the subsequent experiments, suggesting that our findings would be useful for further understanding the physics of atomic doping in VO 2 , which may provide useful guidance for the fabrication of high-quality VO 2 based smart windows. [ABSTRACT FROM AUTHOR]

Capable of achieving wide control over energy band gap and following optoelectronic properties; the highly mismatched alloys (HMAs) are considered to be promising materials for solar energy conversion devices. The dramatic restructuring of energy bands and density of states in HMAs caused by the replacement of anions with distinctly-mismatched isovalent constituents could further be an important course in improving their thermoelectric efficiency. In this paper, we attempt to explore and address the composition-induced modifications in the electronic band structure and the resultant effects on optical spectra and thermoelectric coefficients of GaN 1−x Sb x based HMAs in the framework of density functional theory. We observe, the substitution of N by Sb, considerably affects its band structure and split the conduction band minimum (CBM) into sub-bands. With increasing Sb composition, the lowest sub-band stemmed from N-s electrons has experienced drastic downward shift leading to energy gap narrowing. Interestingly, the energy gap narrowing along R- Γ is found to be faster than that of Γ- Γ point leading to an amazing direct to indirect band gap crossover. On the other hand, the composition-induced energy gap narrowing stimulates the red-shift in fundamental absorption edge in both ultraviolet and the infrared regime, making the GaNSb potentially useful material for photovoltaic applications. In addition, substantial effect on the thermoelectric coefficients of GaNSb is also observed via Sb substitution. We obtain larger Seebeck coefficient, improved power factors and figure of merit (ZT) for GaNSb at low Sb substitution and found diminishing effect with the further increase of Sb composition. With enhanced Seebeck coefficient, power factor and ZT values at modest doping levels, GaNSb alloy could be a promising candidate for near or above room temperature thermoelectric applications. [ABSTRACT FROM AUTHOR]

At both micro- and electronic levels, this paper investigates the effects of Ru-doping on the efficiency of TiO 2 -based dye-sensitized solar cells (DSSCs). A two-layered working electrode design, one for TiO 2 (P-25) and the other for Ru-doped TiO 2 , respectively with and without a p-n junction, is applied. Two calculations based on first principles thermodynamics using the computer software (FactSage) are performed to simulate the chemical equilibria of Ru-TiO 2 particles at 600 °C as well as to demonstrate the ability of Ti and Ru in taking oxygen atoms to form TiO 2 or RuO 2 at 600 °C. Our results reveal a 9.5% increase in open-circuit photovoltage ( V oc ) as well as a 83.4% increase in short-circuit photocurrent density ( J sc ), compared with the DSSC fabricated with a TiO 2 electrode. The observed enhancement in both V oc and J sc can be explained by Ru-modified defect levels in the TiO 2 band gap, which may be the origin of the improved performance. Due to the formation of a p-n junction (p-type Li-doped NiO and n-type Ru-doped TiO 2 ) in the working electrode, the value of V oc has been further increased while maintaining a high J sc . This study advances our fundamental understanding and methodology on metal-doping in general photo-electrodes. [ABSTRACT FROM AUTHOR]

• Systematic study of 3d transition metal-doped CNTs. • V(Cr, Mn, Co)-doped CNTs show spin-polarization effects. • The 3d transition metal doping makes a big difference to the energy band. • 3d transition metal doping increases the quantum capacitance. • Ni-CNT has the largest quantum capacitance near zero potential. Supercapacitors are valued as one of the new green energy storage devices, but the low energy density limits the wide application of supercapacitors. In this paper, the effects of 3d transition metal doped on electronic structure and quantum capacitance of carbon nanotubes are investigated using DFT. The calculations show that elemental doping has caused the break-up of two degenerate states near the Fermi level, quasi-local state changes in the energy band, and the creation of new energy bands. The doping of V(Cr, Mn, Co) causes spin polarization in the energy band. The change in energy band affects the density of states near the Fermi level, effectively increasing the quantum capacitance and surface charge density of the carbon nanotube electrode. The quantum capacitance of Ni-doped carbon nanotubes is the largest, at 59.74 µF/cm2. In the range of water stability, Ti(V, Gr, Mn, Co)-CNT are suitable for use as electrode materials in symmetrical double layer supercapacitors. Sc(Fe, Cu, Zn)-CNT is suitable for use as anode materials in asymmetric double layer supercapacitors. Ni-CNT is suitable for use as a cathode material for asymmetric double layer supercapacitors. This study verifies the feasibility of 3d transition metal doping to improve the quantum capacitance of carbon nanotube electrodes. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, the effects of Al doping and equibiaxial strain on monolayer h-BN were investigated by first-principles calculations. The results show that with tensile strain applied, the structure of the material is more stable, while the structural stability of the material decreases when compressive strain is applied. When the monolayer h-BN is doped with Al, the band gap decreases, and the higher the doped Al concentration, the lower the band gap. Equibiaxial strain is very effective for band gap tuning of monolayer h-BN. The optical calculation results show that the peaks of dielectric function and optical constant of the material decrease after Al doping, and the peaks decrease with the increase of Al concentration. When the strain is tensile, the optical properties of the material will be red-shifted as a whole, and the optical properties of the material will be blue-shifted when compressive strain is applied. After the monolayer h-BN was doped with two Al atoms and a strain of −9% was applied, the optical properties of the material were significantly affected. Our study provides some theoretical implications for the application of monolayer h-BN in the field of spintronic devices and optoelectronic devices. • The effect of equbiaxial strain and Al doping on monolayer h-BN were investigated. • Using first principles based on density functional theory. • Compared with the compression strain, the structure of the material is more stable under the tensile strain. • Band gap decreases with increasing Al doping concentration. • Optical properties of the material are red-shifted with tensile strain and blue-shifted with compressive strain. [ABSTRACT FROM AUTHOR]

Boron nitride nanotubes (BNNTs) are semiconductors with a wide band gap. In comparison with carbon nanotubes (CNTs), BNNTs have higher chemical stability, excellent mechanical properties and higher thermal conductivity. In this paper, we study the effect of diameters and substituting B and N atoms of various zigzag BNNTs with Al, on structural and electronic properties of BNNTs in solid state using the density functional theory method. The results of calculations of density of states and band structure (band) showed that the band gap between the valence and conduction level increases as a result of the enhancement of tube diameter of BNNTs. Finally, the results showed that the electronic properties of the pristine BNNTs can be improved by doping Al atom in the zigzag configuration of tubes. [ABSTRACT FROM AUTHOR]

In this paper, we present the results from first-principles study based on the electronic structure and adsorption characteristics of CH 4 , CO 2 , H 2 and NH 3 adsorbed on Ca decorated/doped phosphorene. Our study finds that phosphorene exhibits n-type behaviour on decorating calcium, and p-type on doping calcium. Gas molecules are physisorbed on both pristine and calcium-mediated phosphorene, visible through their lower binding energy and charge transfer values. Ca decorated phosphorene is suitable for hydrogen storage due to its higher binding energy for H 2 . Ca doped structures shows increased binding affinity towards CH 4 and NH 3 in zigzag1 direction and armchair directions respectively. The extracts of our study implies that Ca doped phosphorene possess increased binding affinity towards gas molecules, and the results are highly helpful for gas adsorption and to design gas sensors based on calcium doped or decorated phosphorene. [ABSTRACT FROM AUTHOR]

In this paper, spin-polarized density functional calculations on the structural, electronic, optical and magnetic properties of the zincblende structure of the and alloys at in the ferromagnetic (FM) ordering has been investigated. The study is accomplished using the full-potential (FP) linearized augmented plane wave plus local orbital (LAPWlo) self-consistent scheme of calculations. To incorporate the exchange correlation component in the total energy calculations of the crystal, Perdew-Burke and Ernzerhof (PBE) parameterization for the generalized gradient approximation (GGA) and GGA U are employed. Basically, for both alloys, to address their structural properties, we calculated their equilibrium lattice constants, bulk moduli as well as pressure derivatives. In general, from the analysis of the obtained electronic band structure of these alloys, the half-metallic nature of and nearly half-metallic nature of the alloy are demonstrated. The plotted density of states (DOS) curves project spin-exchange splitting energy and as generated by V-3 d states. It has been clearly evident that the effective potential results for the spin-down case are more striking than for the spin-up case. In order to describe the magnetic behavior of these alloys, the exchange constants (valence band) and (conduction band) as well as the magnetic moment values are estimated. The calculated results of the magnetic moment show that the main source in the reduction of the local magnetic moment of V in the alloys in comparison with its free value is a - orbital hybridization and partial transfer to nonmagnetic sites of (Zn, S) and (Cd, S) in and alloys. In addition, a study concerning optical properties, such as the refractive index, reflectivity and absorption coefficients is performed to determine their potential for optical and optoelectronic devices. [ABSTRACT FROM AUTHOR]

TiO 2 (titania) is one of the promising materials for photocatalytic applications. In this paper we report on recently obtained theoretical results for N and S doped, as well as N+S co-doped 6-layer (101) anatase nanotube (NT). First principles calculations in our study have been performed using a modified B3LYP hybrid exchange-correlation functional within density functional theory (DFT). Here we discuss the energy of defect formation mechanism and electronic band structure for nanotubes under study. We also report on influence of dopant concentration on the NT's band structure and discuss the defect–defect interactions. [ABSTRACT FROM AUTHOR]

An important feature of the iron-based pnictides is their multi-band electronic structure with both electron and hole bands at the Fermi level. The size of these pockets can be changed by different types of substitution, resulting in a variety of original magnetic and electronic properties. The contributions of both types of carriers will thus have important consequences on the evolution of the transport properties versus temperature and doping. It has been pointed out that Hund's rule interaction plays a prominent role in the physics of these compounds by allowing a strong orbital differentiation between the 3d Fe orbitals. As a result, a description in terms of more or less correlated electrons was proposed and may have important consequences on the scattering lifetimes of the different carriers. Finally, the presence of very flat bands at the Fermi level may induce a semiconductor-like behavior, with a change in carrier concentration with temperature. In this paper, we will review the evolution of transport properties with chemical doping/substitution in iron pnictides. We will more particularly focus on the 122 family (Ba(Sr,Ca)Fe 2 As 2 ) and the 111 LiFeAs compound for which sizeable single crystals required for transport measurements are available. The combined resistivity, Hall effect and magnetoresistance data will be analyzed in association with electronic structure calculations, angle-resolved photoemission measurements and quantum oscillations. In spite of the strong interplay between antiferromagnetism and superconductivity in most part of their phase diagram, direct signatures of spin fluctuations are difficult to identify in the transport properties of iron pnictides. We will show that measurements of the longitudinal magnetoresistance provide a powerful tool for studying the coupling between the charge carriers and the spin degrees of freedom. [ABSTRACT FROM AUTHOR]

To improve the photocatalytic activity of narrow-gap material Bi 2 O 3 , efforts need be made to lower the electron–hole recombination rate and widen the response range of visible light. Understanding the related mechanism is vital, which may lead to high electron-hole mobility and suitable band edge. In this paper we have studied the atomic and electronic structure of single metallic atom (Ag, Cu, Pb, Pd, Sn)-doped and nitrogen (N)-metal codoped Bi 2 O 3 with α phase by first principles calculations. The calculation results firstly show that new impurity states appeared in band gap of α -Bi 2 O 3 after single metal doping, especially for the doping of Cu, Ag and Pb, which showed shallow acceptor levels for α -Bi 2 O 3 . And the formation energy analysis indicates that Cu doped system was easier to be formed than other doped systems. All of those calculated properties are helpful to enhance the photocatalytic property of α -Bi 2 O 3 , which agrees well with experimental results. Interestingly, for anion atom N together with metallic atom (Ag, Cu, Pb, Pd, Sn) codoped α -Bi 2 O 3 systems, it is found that N-2p state had impact on the electronic structure. Holes were demonstrated to be more delocalized in (Cu + N) codoped α -Bi 2 O 3 system, which was responsible for high mobility of holes, then lowering the electron–hole recombination, and finally improving the photocatalytic performance of Bi 2 O 3 significantly. [ABSTRACT FROM AUTHOR]

In this paper, we present a systematic study of the effects of Fe doping on the electronic and magnetic structures of spinel CoCr2O4 by ab initio density functional theory and atomistic spin dynamics calculations. Our calculated magnetic structure for pristine CoCr2O4 correctly reproduces the experimental one with a q-vector of (0.67, 0.67,0.0), establishing the accuracy of the calculated interatomic exchange interactions. We show that the noncollinear spin structure with a nonzero q-vector in the spinel structure is driven towards collinearity by Fe doping by a complex interplay between interatomic exchange interactions. In the inverse spinel structure with 100% Fe doping, a collinear antiferromagnetic order develops along with a half-metallic electronic structure, which evolves due to the chemical disorder between Fe and Co in the B sites described by the coherent potential approximation. This is a comprehensive theoretical study to understand the evolution of magnetic and electronic properties of multiferroic CoCr2O4 doped with Fe. [ABSTRACT FROM AUTHOR]

The microscopic nature of intergranular fracture of NiAl was experimentally investigated by the set of electron spectroscopy techniques. The paper demonstrates that embrittlement of NiAl intermetallic compound is caused by ordering of atomic structure that leads to formation of structural aluminum segregations at grain boundaries (GB). Such segregations contain high number of brittle covalent interatomic bonds. The alloying by La increases the ductility of material avoiding Al GB enrichment and disordering GB atomic structure. The influence of La alloying on NiAl mechanical properties was investigated. GB chemical composition, atomic and electronic structure transformations after La doping were investigated by AES, XPS and EELFS techniques. To qualify the interatomic bonds metallicity the Fermi level ( E F ) position and electrons density ( n eff ) in conduction band were determined in both undoped and doped NiAl. Basing on experimental results the physical model of GB brittleness formation was proposed. [ABSTRACT FROM AUTHOR]

In this paper, the heterofullerenes made of the smallest fullerene, C20were investigated by quantum chemistry calculations based on density functional theory. The geometrical structures, energies, electronic properties, and the aromaticities of the C19X (X = B, N, O, Al, Si, P, S, Ga, Ge, As, and Se) cages were studied systemically and compared with those of the pristine C20cage. It is found that the doped cages with different heteroatoms exhibit various structural, electronic, and aromatic properties. Several doping behaviors of the C19X cages are different from those of the C59X cages. These results imply the possibility to modulate the physical properties of heterofullerenes by tuning the sizes of the carbon cages as well as the substitution elements. [ABSTRACT FROM PUBLISHER]

The adsorption energy, electronic structure, lattice vibration and magnetic properties of Cr, Mn and Fe doped graphene with and without HCN adsorption are investigated by the first principles based on density functional theory. The physisorption and chemisorption have been identified. In the paper, Cr-NG, Mn-NG and Fe-NG denote HCN adsorption on Cr, Mn and Fe doped graphene with N atom toward the adsorption site. It is found that the adsorption energy is −1.36 eV for Fe-NG, −0.60 eV for Mn-NG and −0.86 eV for Cr-NG. The Cr-NG will convert from half-metallic behavior to semiconductor after adsorbing HCN molecule, which indicates that the conductivity changes significantly. Phonon density of states (PDOS) shows that the long range order in graphene can be destroyed by doping Fe, Mn and Cr. The imaginary frequency mode in PDOS suggests that Fe and Mn doped graphene is unstable, while Cr doped graphene is stable. The electronic properties are sensitive toward adsorbing HCN, indicating that Cr doped graphene is a promising sensor for detecting HCN molecule. This study provides a useful basis for understanding of a wide variety of physical properties on graphene. [ABSTRACT FROM AUTHOR]

The absorption edge shifted to long wavelength direction and short wavelength direction of two opposite experimental conclusions have been reported, when the band-gap and absorption spectra of -doped anatase 2 were studied. In order to solve this contradiction, the electronic structure and the optical property of heavy doped anatase 2 have been studied by the first-principles plane-wave ultrasoft pseudopotential method based on the density functional theory with +U method modification. The calculated results indicate that the higher the -doping is, the higher the total energy is, the worse the stability is, the higher the formation energy is, the more difficult the doping is, the wider the optical band-gap is, the more obvious the absorption edge shifting to short wavelength direction is, the lower the absorptivity and the reflectivity is, which is in agreement with the experimental results. The reasonable interpretation of the contradiction has been reported in this paper, too. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the electronic structure and magnetic properties of K and Mn co-doped BaCd2As2 using density functional theory within the generalized gradient approximation (GGA) + U schemes. Calculations show that the ground state magnetic structure of Mn-doped BaCd2As2 is antiferromagnetic while K and Mn co-doped BaCd2As2 is ferromagnetic. Electronic structures indicate that the superexchange mechanism leads to the antiferromagnetic coupling between Mn atoms in Mn-doped BaCd2As2 while the hole-mediated Zener's p–d exchange mechanism leads to the ferromagnetic coupling between Mn atoms in K and Mn co-doped BaCd2As2. [ABSTRACT FROM AUTHOR]

Based on the first-principles plane wave ultra-soft pseudo potential (USP) method of density function theory pure and doped and - codoping anatase 2 supercell models were established, respectively, and calculated their energy in this paper. The calculated results show that the three doping systems compared to the pure anatase 2 band gap narrowed which results in red-shift of the optical absorption edges and - codoped anatase 2 have the most obvious visible effect. Meanwhile, synergy is very effective for the separation of electron-hole pairs and the electrons have a better lifespan. Research found that the trend of the donor's movements at the shallow level of - codoped anatase 2 is not obvious. This is due to its very thick shell, resulting in shielding effect of the outer layer of the -4f. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the structural, electronic and magnetic properties of Ga12N12 cluster doped with monodoped and bidoped atoms within the density functional theory (DFT). Substitutional, exohedral and endohedral doping are considered. It is observed that both monodoped and bidoped clusters tend to be in exohedral doping. Mulliken population analysis is performed to obtain the charge transfer and magnetic moment. The magnetic moment is mainly derived from 3d orbitals of atom for all isomers, while the magnetic properties would rely on the Fe-Fe distance. [ABSTRACT FROM AUTHOR]

The electronic properties of quantum dots have been studied extensively, and recent studies have explored various dopants that can alter electronic properties in quantum dots. Yet, we have found that impurities on the surface of nanometer-scale CdSe materials can also affect electronic properties. Specifically, nitrogen-based impurities on the surface of nanometer-scale CdSe materials (from ~4 to 15 nm) interact with the CdSe conduction electrons to yield an anti-ferromagnetic EPR signal at a high resonance field ( g ~ 0.56) that has an inverse Dysonian lineshape. However, bulk CdSe particles do not show the same types of EPR signals. This paper will discuss these observations, explain the underlying phenomena, and discuss implications for future research. [ABSTRACT FROM AUTHOR]

Being a true two-dimensional crystal, graphene has special properties. In particular, a pointlike defect in graphene may induce perturbations in the long range. This characteristic questions the validity of using a supercell geometry in an attempt to explore the properties of an isolated defect. Still, this approach is often used in ab initio electronic structure calculations, for instance. How does this approach converge with the size of the supercell is generally not tackled for the obvious reason of keeping the computational load to an affordable level. The present paper addresses the problem of substitutional nitrogen doping of graphene. DFT calculations have been performed for 9 x 9 and 10x10 supercells. Although these calculations correspond to N concentrations that differ by ∼10%, the local densities of states on and around the defects are found to depend significantly on the supercell size. Fitting the DFT results by a tight-binding Hamiltonian makes it possible to explore the effects of a random distribution of the substitutional N atoms, in the case of finite concentrations, and to approach the case of an isolated impurity when the concentration vanishes. The tight-binding Hamiltonian is used to calculate the STM image of graphene around an isolated N atom. STM images are also calculated for graphene doped with 0.5 at% concentration of nitrogen. The results are discussed in the light of recent experimental data and the conclusions of the calculations are extended to other point defects in graphene. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the effect of Nb doping on the formation of O vacancies in rutile TiO2 is studied by the use of ab initio density-functional calculations. The formation energies are calculated at different doping concentrations (C Nb ) and the corresponding electronic structures are analyzed. It is shown that the formation energy is mainly determined by the structural relaxation. As C Nb increases, the formation energy first increases and then decreases with the maximum in vicinity of C Nb =11.1at%. The investigation of electronic structures shows that the distribution of excess electrons, which is affected by the doping concentration and the types of oxygen vacancy, determines the relaxation and formation energy of oxygen vacancy. Our calculated results indicate that the formation of oxygen vacancy in rutile TiO2 can be most effectively suppressed by Nb doping in a large range of Nb doping concentration. This may be one of the reasons why the proper amount of Nb doping can improve the oxidation resistance of . [Copyright &y& Elsevier]

[Display omitted] • Two phosphorescent Ir(III) complexes were synthesized and doped into a supporting matrix of bio-MOF-1 via cationic exchange. • Their phosphorescent emission was confirmed by density functional theory and emission lifetime, making them applicable for oxygen sensing. • Linear working curves were observed for both composite samples, showing sensitivity as high as 23.65 with response/recovery time of 9/22 s. • Humidity effect on sensing performance was limited. In this paper, two phosphorescent Ir(III) complexes, Ir(ppy) 2 (Ln), were synthesized using 2-phenyl pyridine (ppy) as the first (major) ligand and two phosphorous compounds (L1 and L2) as the auxiliary ligand. Their single crystal structure and electronic structure were discussed. Ir(ppy) 2 (Ln) complexes were doped into a supporting matrix of bio-MOF-1 via cationic exchange to ensure their uniform distribution. Their successful doping was confirmed by SEM, fluorescence microscopy image, XRD, N 2 adsorption/desorption and ICP measurement. Their photophysical parameters, including absorption spectra, excitation spectra, emission spectra, emission lifetime and quantum yield, were discussed in detail. Their phosphorescent emission was confirmed by density functional theory and emission lifetime, making them applicable for oxygen sensing. Linear working curves were observed for both composite samples, showing sensitivity as high as 23.65 with response/recovery time of 9/22 s. Humidity effect on sensing performance was limited. These parameters were found superior to literature ones based on phosphorescent Cu(I), RE(III), Ru(II) and Re(I) complexes. The sensing mechanism was revealed as a dynamic collision between Ir(ppy) 2 (Ln) and O 2 molecules. The novelty of this work was the combination of phosphorescent Ir(III) complexes with porous bio-MOF-1, resulting in greatly improved sensitivity and linear sensing with short response time. [ABSTRACT FROM AUTHOR]

Monocrystalline silicon is highly promising for applications as semiconductor materials in electronic devices. However, the intrinsic brittleness of Si as well as the relatively low conductivity has restricted its wide application. In this paper, the optimized electronic and mechanical properties of monocrystalline silicon doped with trace content of N or P (SiM x , X = 0, 0.2%, 0.46%, 1.5%, M = N, P) were investigated by first-principles calculations. The results show that the doping of N or P elements can improve the mechanical and electronic properties of monocrystalline silicon, and with the increase of doping concentration, the improving effect becomes more obvious. In addition, the doping of N has a stronger effect on Si than that of P. The doping N, P atoms can form polar covalent bonds to enhance the covalency between atoms, improve the mechanical of Si. Electronic structure analysis shows that the doping of N or P atom makes the hybridization of s-orbital and p-orbital stronger, thus narrows the band gap and improves the conductivity of Si. Furthermore, as the concentration of doping elements increases, Si goes from indirect to direct semiconductor, which is beneficial to improve the recombination of excited electron-hole pairs due to there is no momentum difference between the two positions in k space. [Display omitted] • The effect of doped N, P on the mechanical and electrical properties of Si remains to be explored. • The doping of N has a stronger improving effect on Si than that of P. • The mechanism for the doping of N, P atoms for improving properties of Si are revealed. [ABSTRACT FROM AUTHOR]

The ferromagnetic properties and origin of P doping graphene-ZnO (g-ZnO) monolayer without or with defects including O vacancy (V O) and Zn vacancy (V Zn) are discussed in detail using the first principles method in this paper. In order to describe the electronic structure correctly, the GGA + U (PBE functional in GGA) method is adopted. The most stable structures of P doping g-ZnO monolayer without or with defects including V O and V Zn are obtained. When O atoms in g-ZnO monolayer is replaced by P, the impurity level caused by P is near Fermi level and P-3p orbital is spin polarized, and the system is ferromagnetic. V Zn produce weakly bound O-2p electrons, which spin in the same direction and leads to the ferromagnetism of g-ZnO system. Both of the mechanism can be obtained at room temperature. Meanwhile Curie temperature (T c) of Zn 16 O 15 P 1 and Zn 16 O 14 P 2 is higher than room temperature. Therefore, P doping ZnO monolayer is a potential diluted magnetic semiconductor. [Display omitted] • The stable structures of P doping graphene-ZnO monolayer without or with defects including V O and V Zn are obtained. • The analysis of formation energy (E f) shows that P doping makes g-ZnO films easy to form V Zn. • P doping and V Zn are the ferromagnetic origin of g-ZnO monolayer. • The calculated T c of the designed models is higher than room temperature. [ABSTRACT FROM AUTHOR]

This work reports an experimental and theoretical investigation of pure, Sr, and (Sr,Co) co-doped CdS systems. Pure and co-doped CdS nanostructure thin films were grown with varying Co doping concentrations by sol-gel spin coating method. X-ray diffractograms of the films reveal that the films grow along (002) plane and the crystallites sizes were about ∼3–6 nm. The band gaps of the films were obtained in order of 2.30–2.48 eV and a blue shift in the band gap with co-doping was observed in comparison with Sr:CdS system. In addition, pure and co-doped CdS system were also investigated via density functional theory. Initially, pure and co-doped CdS systems were optimized using WIEN2k software based on density functional theory. The calculated optical properties and band gap reveal a close agreement with the experimental results. The (Sr,Co) co-doped CdS shows the spin polarization effect on the valence band which makes this materials suitable for optoelectronics and spintronics applications. [ABSTRACT FROM AUTHOR]

First-principle calculations have been performed to study the intermetallic alloys MgCoxNi1−x and intermetallic hydrides MgCoxNi1−xH3 using full-potential local orbital (FPLO). The electronic structure of Mg-hydride-based alloys has been elaborated to predict further modifications which destabilize the corresponding hydrides. In this paper, we have demonstrated that the insertion of Co element plays a crucial role in the stability of doped intermetallic hydrides (MgCo0.50Ni0.50H3, MgCo0.75Ni0.25H3 and MgCo0.875Ni0.125H3), by enhancing the hydrogen storage capacities which becomes around 3.488 wt%, also the desorption temperature has improved significantly. Therefore, the mixture between Co and Ni plays an important role in the hydrogen uptake mechanism in the target intermetallic matrix. [ABSTRACT FROM AUTHOR]