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Strain distribution in (InAs) ∕(InSb) multilayer: A first principles calculations
摘要： Using first principles calculations we unveil the interfacial strain relaxation in (wurtzite-InAs)n/(zinc-blend-InSb)m multilayer specimens. We have shown that the distribution of strain along the growth direction depends on the relative thickness of the segments of the multilayer. The observed result has been explained in view of the propagation of lattice deformation due to lattice mismatch between InAs and InSb. To the end we have demonstrated that the fine tuning of the strain with the thickness of layers can be exploited to vary the band gap along the length of the multilayer. The modulation of the band gap in a multilayer system finds various applications in designing optoelectronic devices.
关键词： Strain,First principles calculations,InAs/InSb,Multilayers,Density of states
更新于2025-09-19 17:15:36
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First-principles calculations on effects of Al and Ga dopants on atomic and electronic structures of amorphous Ge <sub/>2</sub> Sb <sub/>2</sub> Te <sub/>5</sub>
摘要： Effects of post-transition metal dopants M (M = Al, Zn, and Ga) on structural and electronic properties of amorphous Ge2Sb2Te5 (a-GST) are investigated through first-principles calculations based on the density functional theory. The doped a-GST is generated through the melt-quench procedure using molecular dynamics simulations. It is found that the three dopants behave similarly in a-GST, and they are mostly coordinated by Te atoms in tetrahedral geometry, which is similar to those in crystalline MxTey. This is in contrast with crystalline GST wherein the most stable position of dopant M is the octahedral vacancy site. The number of wrong bonds such as Ge–Ge, Ge–Sb, or Sb–Sb increases as dopant atoms predominantly bond with Te atoms. The number of 4-fold ring structures, especially ABAB-type, decreases significantly, explaining the enhanced thermal stability of doped a-GST in the experiment. The bandgap estimated from density of states and the optical gap obtained from Tauc plot increase upon doping, which is also in good agreement with the experiment. By successfully relating the experimental doping effects and changes in the atomic structure, we believe that the present work can serve as a key to offer better retention and lower power consumption in phase-change memory.
关键词： amorphous Ge2Sb2Te5,electronic structures,first-principles calculations,atomic structures,Al and Ga dopants
更新于2025-09-19 17:15:36
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Efficient Visible-Light-Induced Photocatalytic Activity of SrTiO <sub/>3</sub> Co-Doped With Os and N: A GGA?+? <i>U</i> Investigation
摘要： A systematic investigation based on spin-polarized DFT + U has been carried out to study the electronic structure of charge compensated (Os, 2N)-codoped SrTiO3 as compared with that of pure SrTiO3, Os-doped SrTiO3, N-doped SrTiO3, and charge non-compensated (Os, N)-codoped SrTiO3. The calculated band gap of pure SrTiO3 is improved to 3.22 eV using GGA + U method by choosing appropriate U values, which is in good agreement with the experimental value (3.25 eV). Although charge non-compensated co-doping with (Os, N) significantly reduces the photoabsorption energy by introducing localized in-gap impurity states of Os-5d, N-2p, and O-2p, unfortunately, the presence of these states may hinder charge carrier mobility. The calculated results show that the charge compensated co-doping with one Os and two N leads to the complete passivation of the mid gap Os-5d and O-2p impurity states, thus the positions of the band edges are extended to satisfy the criteria for overall water splitting under visible-light. The present predictions demonstrate that the charge compensated (Os, 2N)-codoped SrTiO3 can be a desirable effective photocatalyst for highly active visible-light-induced hydrogen production from water splitting due to the enhanced visible-light activity as well as decreased electron–hole recombination rate.
关键词： photocatalytic activity,doping,first-principles calculations,SrTiO3
更新于2025-09-19 17:15:36
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Intercalated complexes of 1T′-MoS <sub/>2</sub> nanosheets with alkylated phenylenediamines as excellent catalysts for electrochemical hydrogen evolution
摘要： Two-dimensional layered MoS2 has recently been considered as an excellent catalyst for the water-splitting hydrogen evolution reaction (HER). Herein, we synthesize 1T0 phase MoS2 that was intercalated with a series of alkylated p-phenylenediamines (PDs). The substituted N atoms produced S vacancies, leading to a composition of MoS2-2xNx (x = 0.1). The more abundant methyl groups induce a larger charge transfer, resulting in excellent HER performance: for tetramethyl PD, the overpotential is 0.15 V at 10 mA cm-2 with a Tafel slope of 35 mV dec-1. The catalytic activity of the complexes depends on the concentration of the intercalated molecules, showing an optimum at a concentration of 8 mol%. First-principles calculations showed that the intercalated complexes (1T0 phase) having N atom–S vacancy (N–VS) pairs are stabilized by a large charge transfer from the PD molecules that is enhanced by the methyl groups (i.e., 0.40e–0.84e per molecule at 6.25 mol% intercalation). The charge transfer increases the density of states at and just above the Fermi level, thereby increasing the electron concentration at low cathodic bias. The active sites for the Volmer reaction are found to be N atoms in the proximal N–VS pairs. The activation barrier for the Heyrovsky reaction becomes higher at higher concentrations of the intercalants, suggesting that the experimental HER performance is also kinetically controlled.
关键词： catalysis,first-principles calculations,MoS2,hydrogen evolution reaction,intercalation
更新于2025-09-19 17:15:36
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Optical absorption in complexes of abasic DNA with noble-metal nanoclusters by first principles calculations
摘要： Optical absorption in complexes of abasic DNA with noble-metal nanoclusters by first principles calculations. Abasic sites (AP site) in a DNA duplex have been experimentally used to produce fluorescent Ag nanoclusters (NC) with a small number of atoms (n ≤ 6). These AP-DNA:NC complexes act as biological markers that help to locate genes associated with diseases related to single nucleotide polymorphisms (SNP), for example. Abasic sites are the most common SNP genetic variation, and their detection may help predict a host of genetically determined diseases. In this work, we report a theoretical study of the optical absorption spectra of AP-DNA:Ag4 and AP-DNA:Au4 complexes using a fully ab initio methodology. We consider several different base environments for the noble-metal nanocluster occupying the AP site, and compute the absorption spectra of sixteen AP-DNA:Ag4 and sixteen AP-DNA:Au4 complexes. We find that optical absorption in the AP-DNA:Ag4 complexes tends to concentrate in the green-to-violet range of frequencies (2.50 eV ≤ ?ω ≤ 3.2 eV) and that AP-DNA:Au4 complexes display absorption peaks in the violet-to-ultraviolet interval (?ω ≥ 3.0 eV). An analysis of the optical absorption mechanisms in these AP-DNA:NC complexes shows that they can be of local, charge-transfer, or hybrid nature, i.e., AP-DNA:NC complexes display the full variety of optical absorption processes in molecular systems. In particular, we identify both charge-transfer and hybrid processes involving several DNA bases surrounding the NC. Importantly, we find that even sequences where the Ag4 cluster is not in a guanine rich neighborhood display absorption peaks in the visible-light spectrum. Moreover, we obtain that the maximum intensities of the absorption peaks in complexes with pyrimidine vacancies are generally higher than those in complexes with purine vacancies. Regarding the selectivity of single-vacancy AP-DNA to specific noble-metal nanocluster sizes, our calculations show that the four-atom Ag4 (Au4) species fits naturally and binds into the AP-site in a single-vacancy AP-DNA.
关键词： noble-metal nanoclusters,optical absorption,first principles calculations,abasic DNA,Au4,charge-transfer,hybrid processes,Ag4
更新于2025-09-19 17:15:36
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Janus Chromium Dichalcogenides Monolayers with Low Carrier Recombination for Photocatalytic Overall Water-Splitting under Infrared Light
摘要： Photocatalytic overall water-splitting is known as one of most promising methods to alleviate energy crisis. Searching for stable and efficient photocatalysts plays a critical role in this process. Here, we propose a novel class of Janus chromium dichalcogenides (CrXY, X/Y = S, Se, Te) monolayers serving as efficient photocatalysts for overall water-splitting under infrared light irradiation. We reveal that these Janus monolayers harbor an intrinsic dipole, which promotes the spatial separation of photo-generated carriers. More significantly, these systems exhibit suitable band gaps as well as band edge positions, enabling preeminent infrared optical absorption and high carrier mobility. Furthermore, the nonradiative recombination of photoinduced charge carriers in CrXY monolayers are evaluated based on time-domain density functional theory. The obtained long-lived excited carriers (~ 2 ns) are even comparable with that in transition-metal dichalcogenides heterostructures, which benefits for the photocatalytic reaction with high efficiency. Our results provide a new guidance for designing brand new photocatalytic systems with broad optical absorption and low carrier recombination.
关键词： infrared light,first principles calculations,carrier recombination,Janus chromium dichalcogenides,photocatalytic water-splitting
更新于2025-09-19 17:15:36
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Tuning the electronic properties of van der Waals heterostructures composed of black phosphorus and graphitic SiC
摘要： This study presents a new van der Waals (vdW) heterostructure composed of monolayer black phosphorus (BP) and monolayer graphitic SiC (g-SiC). Using first-principles calculations, the structural and electronic properties of the BP/SiC heterostructure were investigated. It was found that by stacking BP with SiC, weak type-I band alignment can be achieved with a band gap of 0.705 eV, where the direct band gap as well as linear dichroism features were well preserved. The electrostatic potential drop in the heterojunction was calculated to be 4.044 eV. By applying perpendicular electric field, the band alignment can be altered to either type-I or type-II, and the band gap can be effectively controlled by field intensity, hence making the heterostructure suitable for various applications.
关键词： first-principles calculations,van der Waals heterostructure,graphitic SiC,electronic properties,black phosphorus
更新于2025-09-19 17:15:36
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A novel hydrogenated boron–carbon monolayer with high stability and promising carrier mobility
摘要： Although immense research on the extension of the two-dimensional (2D) material family has been carried out, 2D materials with a satisfactory band gap, high carrier mobility, and outstanding thermodynamic stability under ambient conditions are still limited. In this work, using first principles calculations, we proposed new 2D ternary materials consisting of C, B, and H atoms, namely hexagonal-BCH (h-BCH) and tetragonal-BCH (t-BCH). Both phonon calculations and ab initio molecular dynamics simulations show that these proposed sheets are thermodynamically stable phases. The electronic structure calculations indicate that h-BCH and t-BCH sheets are semiconductors with a band gap of 2.66 and 2.22 eV, respectively. Remarkably, the h-BCH (t-BCH) sheet exhibits electron mobility as high as 7.41 × 10^3 (1.09 × 10^3) cm^2 V^{-1} s^{-1}, which is higher than that of the MoS2 monolayer, though the hole mobility is about one (two) order of magnitude lower. Equally important is the fact that the position of both the conduction and valence band edges of the h-BCH sheet matches well with the chemical reaction potential of H2/H+ and O2/H2O, giving a 2D photocatalyst as a potential candidate for overall visible-light-driven water splitting. Therefore, the designed h-BCH and t-BCH monolayers have promising applications in future electronics and photocatalysts.
关键词： 2D materials,boron-carbon-hydrogen,photocatalysis,first principles calculations,carrier mobility
更新于2025-09-19 17:15:36
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Understanding Molecular Adsorption on CuSCN Surfaces Toward Perovskite Solar Cell Applications
摘要： CuSCN has been employed as the hole transporting material for solar cells and it is established to offer superior power conversion efficiencies and stabilities of the perovskite solar cell. In this manuscript, we carry out first principles calculations to understand the structures and properties CuSCN surfaces in the presence of small molecules that are common in the solution processable solar cells. The molecular adsorbates include additives, precursors and solvents to synthesize the halide perovskite solar cell components such as methylammonium iodide (MAI), lead iodide (PbI2), acetonitrile, chloroform, dimethylformamide (DMF), dimethylsulfoxide (DMSO), methanol and ethanol. The study suggests that the CuSCN surfaces interact with these additive molecules in various degrees and such adsorption is strongly dependent on the CuSCN surface directions. The presence of the PbI2 moiety leads to additional empty states inside the band gap of CuSCN. The presence of the molecular adsorbates impacts on the electronic and optical properties of the CuSCN surfaces, and further additive-based interfacial engineering approach of the perovskite/CuSCN system is called for. This study paves the way toward the fundamental understanding of the CuSCN surfaces toward optoelectronic applications.
关键词： perovskite solar cells,optoelectronic applications,CuSCN,molecular adsorption,first principles calculations
更新于2025-09-19 17:13:59
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Coupled structural distortions, domains, and control of phase competition in polar
摘要： Materials with coupled or competing order parameters display highly tunable ground states, where subtle perturbations reveal distinct electronic and magnetic phases. These states generally are underpinned by complex crystal structures, but the role of structural complexity in these phases often is unclear. We use group-theoretic methods and first-principles calculations to analyze a set of coupled structural distortions that underlie the polar charge and orbitally ordered antiferromagnetic ground state of A-site ordered SmBaMn2O6. We show that these distortions play a key role in establishing the ground state and stabilizing a network of domain wall vortices. Furthermore, we show that the crystal structure provides a knob to control competing electronic and magnetic phases at structural domain walls and in epitaxially strained thin films. These results provide new understanding of the complex physics realized across multiple length scales in SmBaMn2O6 and demonstrate a framework for systematic exploration of correlated and structurally complex materials.
关键词： phase competition,first-principles calculations,domains,coupled structural distortions,group-theoretic methods,polar SmBaMn2O6
更新于2025-09-16 10:30:52