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This research investigates the electronic, optical, elastic, and mechanical characteristics of cubic Cesium Lead Iodide CsPbI₃ perovskite by utilizing the Generalized Gradient Approximation method under varying stress conditions ranging from 0 to 13GPa. Using the Density Functional Theory, the research demonstrates that electronic parameters, such as the electronic band gap, the partial density of states, and the total density of states, are impacted by applied stress. The band gap becomes zero at 14GPa. Significant changes are also noted in optical parameters, such as absorption, conductivity, reflectivity, dielectric function, loss function, and refractive index. The study also identifies changes in elastic properties, including elastic constants as well as an exponential rise in mechanical properties, such as Young’s modulus, bulk modulus, and shear modulus. Furthermore, the study finds that Poisson’s ratio, Cauchy pressure, Pugh’s ratio, and Frantsevich’s ratio experience irregular changes. These discoveries provide valuable insights into the properties of CsPbI₃, which could aid in the development of semiconducting devices, transparent coatings, and lenses.

A study of the crystal structure, mechanical and acoustic properties of two $P{2}_1∕a$ and $P{2}_1∕c$ monoclinic phases of naphthalene and anthracene was performed using ab initio method of linear combination of atomic orbitals (LCAO) and basis sets: C_6-21G*, H_3-1p1G. The method was implemented in the CRYSTAL${}^{\prime }$14,${}^{\prime }$17 software package using electron density functional theory including van der Waals interactions (DFT-D2 and DFT-D3 (BJ)), in the local density approximation (LDA) with VWN exchange-correlation potential, gradient approximation PBE exchange-correlation functional and B3LYP hybrid functional. The calculated elastic constants for the first time are in moderate agreement with experimental data. Bulk modulus $B$, shear modulus $G$, Young’s modulus $E$ and the Poisson’s ratio $\mu$, as well as acoustic properties (average velocity of sound $〈v〉$, the Debye temperature ${\mathrm{\Theta }}_D$, and acoustic Grüneisen parameter ${\gamma }_a$) were obtained using the Voigt–Reuss–Hill model.

The layer-dependent optoelectronic properties of monolayer, bilayer and trilayer black phosphorus (BP) are studied by using the first-principles calculations based on density functional theory (DFT). The valence band splits and the density of states (DOS) in the conduction band obviously shift to the Fermi surface with the increased layer number. The atomic p orbital of BP plays an decisive role in determining the electronic and optical properties, which are drastically different from those of graphene and transition metal dichalogenides (TMDs). The increase of the layer number leads to the metal characteristics. The extinction coefficient and photoconductivity show strong optical responses to the ultraviolet (UV) light, which further increase with the number of layers. BP layers can reflect UV rays effectively because of their metallic properties in the UV energy range. Our study shows that the interlayer interaction can intensely change the electronic and optical properties of BP.

Using first-principles calculations based on density functional perturbation theory, we demonstrate hydrogenation-induced superconductivity in monolayer TiB₂H. Hydrogen adatoms destroy the Dirac state of monolayer TiB₂ and monolayer TiB₂H has a high vibration frequency. Monolayer TiB₂H is a phonon-mediated superconductor. Monolayer TiB₂H has a predicted $T_c$ of 8K, which further increases under external tensile strain. Thus, this study extends our understanding of superconductivity in two-dimensional (2D) materials and its potential applications.

We employed a first-principles method based on the density functional theory to investigate the effect of impurity O on the site preference and elastic properties of α₂-Ti₃Al. We found that the O atom prefers to occupy the Ti-rich octahedral interstitial site in α₂-Ti₃Al. We calculated the elastic constants of α₂-Ti₃Al with single O atom, which demonstrate that the O presence has no large effect on α₂-Ti₃Al according to the empirical criterions. Other factors such as O cluster should be taken into account to understand the deleterious effect of O on α₂-Ti₃Al. Our results provide a useful reference to further study the mechanical properties of TiAl alloys.

In this study, density-functional theory plane-wave pseudopotential method was employed to investigate several oxygen vacancies on TiO₂ anatase (101) surface. At first, a suitable defect-free slab model has been established by analyzing the surface energies and the atomic relaxations influenced by different technical parameters. The formation energies of different kinds of oxygen vacancies in the outermost layer have also been compared as well as the atomic displacement of the defective surfaces. It was found that the presence of bridging oxygen vacancy is more energetically favored and causes larger atomic displacement than other types of surface oxygen vacancies. The reactivity of oxygen vacancies has also been tested by both molecular and dissociated oxygen adsorption. Furthermore, we discussed the configurations and the electronic properties of O₂-adsorbed surface, and found that the appearance of oxygen adsorbate-induced states in the band gap can make the surface sensitive to visible light.

Effects of oxygen vacancy (Vo) on magnetic properties of Co-doped ZnO are investigated by first principle calculations. The calculated formation energies of Vo with different bonding to Co atom indicate that Vo prefers location near Co atom, implying a strong local interaction between the Co atom and O-vacancy. Induced by Vo, the Co-3d and O-2p valence bands upward shift towards the Fermi level, leading to the presence of additional carriers at the Fermi level. The delocalized carriers and the substitutional Co ion play a key role in the occurrence and stability of ferromagnetism of Co-doped ZnO.

Current-induced spin-transfer torques (STTs) have been studied in Fe, Co and Ni domain walls (DWs) by the method based on the first-principles noncollinear calculations of scattering wavefunctions expanded in the tight-binding linearized muffin-tin orbital (TB-LMTO) basis. The results show that the out-of-plane component of nonadiabatic STT in Fe DW has localized form, which is in contrast to the typical nonlocal oscillating nonadiabatic torques obtained in Co and Ni DWs. Meanwhile, the degree of nonadiabaticity in STT is also much greater for Fe DW. Further, our results demonstrate that compared to the well-known first-order nonadiabatic STT, the torque in the third-order spatial derivative of local spin can better describe the distribution of localized nonadiabatic STT in Fe DW. The dynamics of local spin driven by this third-order torques in Fe DW have been investigated by the Landau–Lifshitz–Gilbert (LLG) equation. The calculated results show that with the same amplitude of STTs the DW velocity induced by this third-order term is about half of the wall speed for the case of the first-order nonadiabatic STT.

Using first-principles calculation we investigated the structural, electronic and elastic properties of paramagnetic CaFeAs₂. Our results indicated that the density of states (DOS) was dominated predominantly by Fe-3$d$ states at Fermi levels, and stronger hybridization exists between As₁ and As₁ atoms. Three hole pockets are formed at $\mathrm{\Gamma }$ and Z points, and two electronic pockets are formed at A and E points. The Dirac cone-like bands appear near B and D points. For the first time we calculated the elastic properties and found that CaFeAs₂ is a mechanically stable and moderately hard material, it has elastic anisotropy and brittleness, which agrees well with the bonding picture and the calculation of Debye temperature (${\mathrm{\Theta }}_{\mathrm{\text{D}}}$).

The structural properties, formation heats, cohesive energies, elastic properties and electronic structures of common intermetallics in CrMnFeCoNiZr system high-entropy alloys are analyzed by using density functional theory. The calculation results show that Co₁Zr₁, Co₂Zr₁, Fe₂Zr₁ and Fe${}_{23}$Zr₆ phases may form in the casting process of the alloy, which indicates good agreement with the XRD results of the self-designed alloys. The calculated elastic constants reveal that Co₂Zr₁, Fe₂Zr₁ and Fe${}_{23}$Zr₆ are mechanically stable. In addition, the results show that Co₂Zr₁, Fe₂Zr₁ and Fe${}_{23}$Zr₆ with high shear modulus and elastic modulus would be excellent strengthening phases in high-entropy alloy and would improve the hardness of the alloys.

RE site ionic radius has a critical influence on the properties of double perovskite oxide Ba₂RENbO₆. In this paper, the electronic structures and elastic properties of Ba₂RENbO₆ (RE = Ho, Er, Yb) have been calculated by using the plane-wave pseudopotential density functional theory, and the effect of the different RE site ions on the structures and properties of Ba₂RENbO₆ is discussed. Results indicate that Ba₂RENbO₆ (RE = Ho, Er, Yb) are all direct bandgap semiconductors with a bandgap of 0.95 eV, 1.26 eV and 2.36 eV, respectively. With the decrease of the RE site ionic radius of Ba₂RENbO₆ (RE = Ho, Er, Yb), RE–O and Nb–O covalent bonds are enhanced, and the elastic constants ($c_{11}$, $c_{12}$, $c_{44}$), elastic modulus ($B$, $G$, $Y$), $B/G$, Poisson’s ratio ($\sigma$), the Debye temperature $\mathrm{\Theta }$, Gruneisen parameters $\zeta$ all show a trend of increase. The elastic and thermodynamic properties are all improved with the decreasing radius of RE site ion.

The structure of ZrB₂ under high-pressure was predicted by Particle Swarm Optimization method (CALYPSO). We investigated the structure stability, phonon dispersion curve, elasticity, electronic structure and thermodynamic properties of ZrB₂ under high-pressure and high-temperature via first-principles calculations. It maintained the hexagonal structure when the pressure lowers below 600 GPa at 0 K, which is confirmed by the calculated phonon dispersion curve. Studies indicate that the elastic modulus and Poisson’s ratio increase monotonically with pressure, as supported by some theoretical and experimental evidences. Calculated anisotropic factors demonstrate that compression and shear isotropy of ZrB₂ weakens as the pressure increases. Using the quasi-harmonic approximation Debye model, the Debye temperature, sound velocity, expansion coefficient, thermal capacity under the high-temperature and pressure were also predicted.

First-principles method based on density functional theory has been performed to study the lattice structures, elastic properties, Debye temperatures, electronic properties and phase stability of Ni–Sc intermetallic compounds systematically. The calculated lattice parameters are close to available experimental data. The analysis results of formation enthalpies indicate that the Ni–Sc compounds are all thermodynamically stable and NiSc is the most stable. Besides, these compounds are also mechanically stable according to the mechanical stability criterion. The obtained shear modulus G and Young’s modulus E show that Ni₅Sc is the stiffest and the most covalent compound. The discussion about G/B (the ratio of shear modulus to bulk modulous), Poisson’s ratio $\nu$ and Cauchy pressure demonstrate that all Ni–Sc compounds are ductile and NiSc₂ is the most ductile phase, followed by NiSc. The results of Debye temperatures indicate that Ni₅Sc has the stronger covalent bonds than others. Finally, the electronic properties are investigated to reveal the underlying mechanical properties.

Two-dimensional (2D) materials with robust ferromagnetism properties have high potentials for application in the field of spintronics. However, extensively pursued 2D sheets, including pure graphene, monolayer BN, and layered transition metal dichalcogenides, are either nonmagnetic or weakly magnetic. The elastic, electronic and magnetic properties of monolayer CrN are calculated using the plane wave pseudo potential method based on first-principles density function theory. Upon determining through calculation that the structure of the monolayer CrN nanosheet is stable, its layer modulus ${\gamma }_0=330.2{\mathrm{\text{Nm}}}^{-1}$ shows that its strain resistance is stronger than that of graphene. Through strain analysis, materials with a monolayer CrN type of structure can be obtained. It is determined that 10% of the change in equilibrium area is still applicable to the 2D EOS, showing that this structure is quite stable. The spin-polarized electronic band structure is also calculated under different plane symmetry strains. The plane strain can be used to effectively adjust the metallic and magnetic properties of the material. Analyses of the band structure and density of states reveal that this material is half-metallic, where the origin of the ferromagnetism is related to $p$–$d$ exchange interactions between the Cr and N atoms. Monolayer CrN has semimetallic properties and strong ferromagnetic (FM) properties. The FM effect can enhance the stability of the material. The results show that monolayer CrN is a semimetallic material with good elastic properties and a strong FM property. This material is therefore expected to have good application rospects in the field of spin electronics.

Based on the first-principles density-functional theory, the structural, electronic, elastic and dielectric properties of RbLi₂(NH${}_2{)}_3$, LiH and LiNH₂ are calculated. We have analyzed the bond information in detail, where the atom Li in crystal is represented in ionic characteristics mostly. The small covalent bond behaviors are also captured between atom Li and others. The ionic characteristics with tiny covalent bonds are obviously beneficial to electrons for storage capacity and transferring. The mechanical properties of three crystals reveal that LiH has a strong resistance to deformation. It is predicted that LiH has a long service life as a battery in terms of deformation. The dielectric constant reveals that LiH has a better storage capacity than that of LiNH₂. Additionally, LiH has low formation energy, where the harder substance is, the easier formation is.

The electronic structures of nitrogen (N)-doped TiO₂ anatase (101) surfaces have been investigated by density functional theory (DFT) plane-wave pseudopotential method with general gradient approximation (GGA) + U (Hubbard coefficient) method being adopted to describe the exchange-correlation effects. Both substitutional and interstitial N doping have been considered in this paper as well as the case of surface N adsorption. The results demonstrated that there is no obvious band gap narrowing observed by introducing N impurities except several N 2p states lying in the gap, whereas the introduction of oxygen vacancy was confirmed playing an important role on band gap narrowing. The results accord well with some experimental results.

Mechanical properties and the effect of metallic bonding on the hardness of transition-metal nitrides (TiN, VN and CrN) compounds are studied using the first-principles calculation. Present results show that these transition-metal nitrides are mechanically stable and the VN and CrN are ductile, whereas TiN is predicted to be brittle. Moreover, it is found that the high hardness of TiN, VN and CrN exhibits a remarkable decrease with transition-metal changed from Ti to Cr, and the metallic d–d interactions play important roles on determining the hardness of transition-metal nitrides.

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.

First-principles calculations within density functional theory (DFT) with the projector augmented wave (PAW) technique were used to investigate the stabilities of intermetallics in the Au–Rb system at 0 K. Four intermetallics: Au₇Rb₃, Au₃Rb₂, Au₅Rb and AuRb were investigated in their observed experimental structures. The Au₂Rb compound, reported in the Au–Rb phase diagrams without specifying explicitly its structure, was also investigated by inspecting several hypothetical structures. A suspect compound (AuRb₂) was also investigated. Results show that: (i) The Au₃Rb₂ and Au₇Rb₃ compounds, which were never reported in any Au–Rb phase diagram, are stable at 0 K. (ii) The Au₂Rb compound is not a ground state for all the tested structures. (iii) Stability of the Au₅Rb and AuRb compounds was confirmed. (iv) The new compound AuRb₂, not yet reported experimentally, is found mechanically stable at 0 K.

First-principle calculations have been performed to systematically investigate structural and electronic properties of InPBi alloys. The formation energy of seven different configurations is studied. The strength of covalent bonding largely depends on the strong s–p hybridization among In-5s, P-3p and Bi-6p states. The band gap of InPBi shrinks clearly with the increasing Bi concentration and the band edge shifts when spin-orbit coupling (SOC) is considered. The insertion of Bi atom leads to hybridization of In/P/Bi p states which contributes a lot around Fermi level. In addition, our results show that the biaxial strain is an effective method to tune the electronic properties of the system.