Vienna Ab Initio Simulation Package Research Articles

RASCBEC: Raman spectroscopy calculation via born effective charge

We present a reformulated algorithm for ab initio calculations of Raman spectra for large systems by applying an external electric field, and complement it by a code implementation we name RASCBEC. With the RASCBEC code, we have successfully benchmark crystalline materials and compute Raman spectra of large molecules, and amorphous oxides. Our results demonstrate a remarkable level of agreement with the results from other commonly used codes as well as the experimental data. The electric field approach for Raman spectra calculation is designed to overcome the computational challenges associated with the conventional method, which requires calculating the macroscopic dielectric tensor at numerous molecular geometries. This approach is favored because it can significantly reduce computational time. We reformulated this method by obtaining the Raman intensity from the first-order derivative of the Born Effective Charge (BEC), which is computed directly from vasp (the Vienna Ab Initio Simulation Package). This differs from other electric field-based methods that calculate Raman intensities as the second-order derivative of force with respect to the electric field. By reducing the order of derivatives, we can avoid numerical noise and accuracy concerns. Additionally, since forces are often very small numbers, taking the derivative of BEC is numerically more stable, allowing our method to be applied to a broader range of material parameters. This advantage makes RASCBEC particularly beneficial for large molecules and extensive amorphous systems.

Integrating Theoretical and Experimental Approaches to Unveil the Mechanical Properties of CuSbSe2 Thin Films

Abstract An exhaustive investigation of the mechanical characteristics of CuSbSe2 (CASe) thin films is conducted in this study by combining experimental nanoindentation methods with theoretical simulations. The Ab-initio Molecular Dynamics (AIMD) calculations are performed with the machine learning (ML) force fields. By employing the Vienna Ab-initio Simulation Package (VASP) based on Density Functional Theory (DFT), theoretical inquiries are carried out to identify crucial parameters, such as bonding characteristics, elastic constants, hardness, bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio. Experimental validation is conducted using nanoindentation to investigate load-dependent hardness and Young’s modulus in a manner that closely matches the theorized predictions. The anomalies between experimental and theoretical outcomes are ascribed to anisotropic behavior and grain boundaries. Furthermore, an investigation is conducted into the directional dependence of sound wave velocities in the CASe films, leading to the revelation of intricate elastic property details. By employing an integrated theoretical-experimental approach, the present attempt not only increases the knowledge concerning CASe films but also fortifies the relationship between theory and experiment, thereby bolstering the dependability of our results. The insights provided as a result of this paper facilitate the development of CASe film applications in a variety of technological fields in the future.

Research on N, Ne, and P adsorption on boron-germanene nanoribbons for nano sensor applications

The study investigated the adsorption of N, P, and Ne atoms on boron-germanene nanoribbons (BGeNRs) using density functional theory (DFT) and the Vienna Ab initio Simulation Package (VASP). Results indicated that both the pristine and adsorbed configurations exhibited metallic behavior. While the pristine and Ne-adsorbed configurations were nonmagnetic, the N- and P-adsorbed configurations displayed magnetic moments of 1.81 μB and 1.21 μB, respectively. The N-adsorbed configuration had the lowest adsorption energy, whereas the Ne-adsorbed configuration exhibited a positive adsorption energy. Multi-orbital hybridization analysis revealed that hybridization processes predominantly occurred in the conduction band at energy levels corresponding to the σ bond. Charge density difference analysis showed significant charge transfer between the substrate and the adsorbed elements. Additionally, optical properties, including the real and imaginary parts of the dielectric function, absorption coefficient, and electron-hole density, were systematically examined to highlight the variations. The findings underscore the potential application of BGeNR materials in nanosensors.

Exploring the Physical Properties of LiBeX (X = Sb, Bi) Compounds via Ab Initio Approach

In the current study, it is aimed to scrutinize the physical properties of LiBeX (X = Sb, Bi) compounds in detail. Density‐functional‐theory‐based WIEN2k and the Vienna Ab initio Simulation Package, employing the generalized gradient approximation of Perdew–Burke–Ernzerhof, Wu–Cohen, and Tran–Blaha‐modified Becke–Johnson (TB‐mBJ) exchange‐correlation schemes, are utilized to better validate the outcomes. The compounds exhibit energetic, lattice dynamic, and mechanical stability. Electronic structure calculations using the TB‐mBJ functional reveal indirect bandgaps of 1.007 eV for LiBeSb and 0.789 eV for LiBeBi compounds, respectively. The partial charge distribution in the highest occupied molecular orbital and the lowest unoccupied molecular orbital discloses maximum charge localization around the X site. The examination of the crystal orbital Hamilton population reveals the strongest BeX bonding interactions among the bonding pairs. The physio‐mechanical properties indicate brittle and mechanically anisotropic behavior of both compounds, with covalent bonding characteristics. The comparative analysis suggests that the TB‐mBJ potential is suitable for bandgap calculations due to its close alignment with experimental results. Additionally, the optimized results for these compounds indicate their potential for use in optoelectronic devices, such as visible to ultraviolet sensors and photovoltaics. The determined properties are consistent with previous theoretical findings.

Theoretical Insights into Off-Stoichiometric Zr(x)Ti(1-x)IrSb Half-Heusler Alloys: A First Principle Calculations.

This study presents a theoretical investigation into the phase stability, electronic, and optical properties of off-stoichiometric Zr_{x}Ti_{1-x}IrSb (x = 0, 0.0625, 0.1875, 0.25, 0.50, 0.75, 1) compounds. Using first-principles calculations, we explore how varying Zr and Ti concentrations can tune the electronic and optical properties of these half-Heusler alloys. The Structural, optical, and electronic properties were meticulously analyzed with both the GGA-PBE and Meta-GGA-SCAN approximations, as implemented in the Vienna Ab initio Simulation Package (VASP). The dynamical stability of these compounds was assessed using the Phonopy package. Our findings reveal that these alloys exhibit semiconductor behavior with tunable band gaps, and their optical properties show significant variation across different compositions, particularly in the visible light range. The compounds also demonstrate robust dynamical stability, indicating their potential for practical applications in electronic and optoelectronic devices. These results underscore the versatility of Zr_{x}Ti_{1-x}IrSb alloys and highlight their promise for next-generation technology.

Ultralow thermal conductivity and excellent thermoelectric performance in Janus Bi2X2Y (X=Se, Te; Y=S, Se, Te) monolayers induced by suppressed membrane effect

We use density functional theory (DFT) implemented in the Vienna Ab initio Simulation Package (VASP) combined with Boltzmann transport equations to investigate the relationships between the structure, phonon hybridization, transport and thermoelectric properties of two-dimensional (2D) Janus Bi2X2Y (X=Se, Te; Y=S, Se, Te) monolayers. Among them, Janus Bi2Te2S monolayer shows a unique ultralow lattice thermal conductivity (1.09 W·m−1·K−1 at 300 K) and excellent thermoelectric performance. We find that, by suppressing the membrane effect of 2D materials to enable the negative-positive conversion of the Grüneisen parameter of the out-of-plane acoustic (ZA) phonon modes, the three-phonon scattering of the material can be effectively enhanced thereby reducing their lattice thermal conductivity. Besides, we also find the suppression of the membrane effect is highly correlated to the non-orthogonal bond angles. Our results indicate a new path to reduce the lattice thermal conductivity of 2D materials and are meaningful for further theoretical and experimental research on the development of high-performance thermoelectric materials.

Preparation of highly graphitized porous carbon and its ethane/ethylene separation performance

The efficient separation of ethane (C2H6) and ethylene (C2H4) is crucial for the preparation of polymer-grade C2H4, necessitating the development of highly selective and stable C2H6/C2H4 adsorbents. Highly graphitized porous carbon, denoted GC-800, was synthesized by polymerization at room temperature followed by carbonization at 800 °C using phenolic resin as the precursor and FeCl3 as the iron source. Vienna Ab-initio Simulation Package (VASP) calculations confirmed a higher binding energy between C2H6 molecules and graphitized porous carbon surfaces, so that a high degree of graphitization increased the adsorption capacity of porous carbon for C2H6. However, catalytic graphitization using Fe at high temperatures disrupted the microporous structure of the carbon, thereby reducing its ability to separate C2H6/C2H4. By controlling the carbonization temperature, the degree of graphitization and pore structure of the porous carbon could be changed. Raman spectra and XPS spectra showed that the GC-800 had a high degree of graphitization, with a sp2 C content as high as 73%. Low-temperature N2 physical adsorption measurements estimated the specific surface area of GC-800 to be as high as 574 m2·g−1. At 298 K and 1 bar, it had an equilibrium adsorption capacity of 2.16 mmol·g−1 for C2H6, with the C2H6/C2H4 (1:1 and 1:9, v/v) ideal adsorbed solution theory selectivity respectively reaching 2.4 and 3.8, significantly higher than the values of most reported high-performance C2H6 selective adsorbents. Dynamic breakthrough experiments showed that GC-800 could produce high-purity C2H4 in a single step from a mixture of C2H6 and C2H4. Dynamic cycling tests confirmed its good cyclic stability, and that it could efficiently separate C2H6/C2H4 even under humid conditions.

Excavating oxygen vacancies in BaZrO3 to boost photocatalysis via screening vantage crystal planes

Investigations into the design and advancement of oxygen vacancies (OVs) are at the forefront of high-efficiency catalyst research. However, the lack of experimental evidence and a comprehensive mechanistic understanding regarding the promotion of OVs poses challenges. Herein, we investigate the role of crystal planes in elucidating the mechanism of OVs formation and their impact on photocatalytic hydrogen evolution. Initially, the Vienna ab-initio simulation package was utilized to calculate the key characteristics and band parameters of BaZrO3, subsequently, the screening crystal planes of (110) was synthesized. Experimental findings indicated that the (110) crystal plane increased the OVs rate from 32 % to 56 %, consequently improving photocatalytic hydrogen evolution performance from 13.1 to 20.5 mmol·g−1·h−1. Furthermore, theoretical calculations were employed to delve into both OVs formation mechanisms and catalytic activity. This study presents an innovative approach for strategically modifying catalyst OVs for efficient and high-performance photocatalytic applications.

Investigation of Be, Mg, Ti-adsorbed boron-germanene nanoribbons for nano applications.

One-dimensional systems are nanostructures of significant interest in research due to their numerous potential applications. This study focuses on the investigation of one-dimensional boron-germanene nanoribbons (BGeNRs) and BGeNRs doped with Be, Mg, and Ti. Density functional theory (DFT) combined with the Vienna Ab initio Simulation Package (VASP) forms the foundation of this research. The electromagnetic and optical properties of these structures are systematically examined. The findings reveal that all the studied structures exhibit metallic behavior, with differences in their magnetic properties. The magnetic moments of the pristine and Be-doped structures are both zero, whereas the Mg and Ti-doped structures exhibit magnetic moments of 0.012 μB and 2.234 μB, respectively. Partial density of states (PDOS) analyses highlight the contributions of various elements and the complex multi-orbital hybridization among them. The optical properties are investigated through the real and imaginary parts of the dielectric function, along with the absorption coefficient and electron-hole density. This study indicates potential applications in adsorption sensors, the modulation of system magnetism via adsorption, and information transmission technologies.&#xD.

First-principles data for solid solution niobium-tantalum-vanadium alloys with body-centered-cubic structures

We present four open-source datasets that provide results of density functional theory (DFT) calculations of ground-state properties of refractory solid solution binary alloys niobium-tantalum (NbTa), niobium-vanadium (NbV), tantalum-vanadium (TaV), and ternary alloys NbTaV ordered in body-centered-cubic (BCC) structures with 128 Bravais lattice sites. The first-principles code used to run the calculations is the Vienna Ab-Initio Simulation Package. The calculations have been collected by uniformly sampling chemical compositions across the entire compositional range. For each chemical composition, the calculations have been run for 100 randomized arrangements of the constituents on the BCC lattice sites. This sampling methodology resulted in running DFT simulations for a total of 3,100 randomized atomic configurations over 31 chemical compositions for each of the three binary alloys Nb-Ta, Nb-V, Ta-V, and a total of 10,500 randomized atomic structures over 105 chemical compositions for the ternary alloys Nb-Ta-V. For each atomic configuration, geometry optimization has been performed, and the data released contains information about each step of geometry optimization for each atomic configuration.

Mechanistic investigation of methanol-to-olefins conversion catalyzed by H-ZSM-5 zeolite: a DFT study.

The mechanisms for the formation of the first C - C bond and lower olefins on methanol to olefins (MTO) conversion on H-ZSM-5 had been focused in dispute. In this paper, density functional theory has been used to study the reaction mechanisms of methanol to olefins on ZSM-5. The configurations of reactants, intermediates, products and transition state of the numerous reactions involved in such a process have been optimized, as well as the elementary reactions related to these configurations were determined by the calculation of corresponding activation energy barriers and reaction heats. Here, two different kinds of the mechanisms were proposed for the formation of dimethylether (DME), one involving an associative interaction of two methanol molecules with the zeolite Brønsted acid sites and the other occurring via a surface methoxy species and a methanol molecule. A critical intermediate of the methoxy methyl cation was theoretically verified by the reaction of the methoxy species and dimethylether. Besides, it was found that the first intermediates containing a C - C bond were 1,2-dimethoxyethane and 2-methoxy-ethanolare, in which the former was formed from methoxy species with dimethyl ether and the latter was formed from methanol by onium ions((CH3)2O+CH2CH2OCH3), respectively. For the whole reaction mechanism, the results in this paper indicated that the ethene formation is more favorable than propylene formation due to the low activation energy barrier for ethene formation (123.49 vs. 162.09kJ.mol-1). From these calculations, it would be concluded that ethene is the first alkene product that induces the occurrence of the hydrocarbon pool mechanism. All the periodic density function theory (DFT) calculations were performed by the Vienna Ab Initio Simulation package (VASP). The interaction between nucleus and valence electron was described using the pseudopotentials found in the projector augmented wave (PAW) method. PBE-D3 was used in the whole DFT calculations and CI-NEB was used to locate transition state.

Ab Initio Modelling of g-ZnO Deposition on the Si (111) Surface

Recent studies show that zinc oxide (ZnO) nanostructures have promising potential as an absorbing material. In order to improve the optoelectronic properties of the initial system, this paper considers the process of adsorbing multilayer graphene-like ZnO onto a Si (111) surface. The density of electron states for two- and three-layer graphene-like zinc oxide on the Si (111) surface was obtained using the Vienna ab-initio simulation package by the DFT method. A computer model of graphene-like Zinc oxide on a Si (111)-surface was created using the DFT+U approach. One-, two- and three-plane-thick graphene-zinc oxide were deposited on the substrate. An isolated cluster of Zn3O3 was also considered. The compatibility of g-ZnO with the S (100) substrate was tested, and the energetics of deposition were calculated. This study demonstrates that, regardless of the possible configuration of the adsorbing layers, the Si/ZnO structure remains stable at the interface. Calculations indicate that, in combination with lower formation energies, wurtzite-type structures turn out to be more stable and, compared to sphalerite-type structures, wurtzite-type structures form longer interlayers and shorter interplanar distances. It has been shown that during the deposition of the third layer, the growth of a wurtzite-type structure becomes exothermic. Thus, these findings suggest a predictable relationship between the application method and the number of layers, implying that the synthesis process can be modified. Consequently, we believe that such interfaces can be obtained through experimental synthesis.

Aptamer Encapsulated Inside the Array Channel of Ni‐MOF for Bisphenol A Determination in Multi‐interference System

AbstractAs an endocrine disruptor, bisphenol A (BPA) has many adverse effects on environmental safety and human health. Aiming at the existing problems at the current detection methods, herein, a 3D metal‐organic framework (Ni‐MOF) was fabricated as a carrier to achieve BPA aptamers immobilization inside its array channels under Mg2+ regulation. Based on the reversible quenching of 6‐FAM (6‐carboxyfluorescein) fluorescence labeled on the BPA aptamers during the encapsulation process, a fluorescent aptamer sensing platform was constructed for the quantitative detection of BPA in water. Morphology analysis, VASP (Vienna ab‐initio simulation package) and other kinetic simulations were performed to elaborate the mechanism of the influence of pore size, medium ions, etc. on the recognition process. Due to the in‐hole fixation strategy of aptamers, Ni‐MOF played an obvious protection aptamers. Not only the activity of BPA aptamer@MOF composite was maintained more than 50 % in complex environments such as pH 3.0–11.0, 30–70 °C and organic solvents, but also the aptamer was protected from nuclease hydrolysis under physiological conditions. The stability and application range of the sensor are greatly improved, detection limit of 0.34 μM. The result was expected to provide theoretical guidance for the rapid detection of pollutants in complex environments.

Orange-reddish emitting of trivalent samarium doped double perovskite Sr2LuNbO6 with high thermal stability for white-LED application

A series of trivalent samarium ions (Sm3+) doped double perovskite Sr2LuNbO6 (x at% Sm3+:Sr2LuNbO6, x = 0.5–15) phosphors have been prepared via high-temperature solid-state method. The structural characterization of these phosphors was conducted employing X-ray diffraction (XRD), XRD Rietveld refinement, scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. Density functional theory calculations utilizing the Vienna ab initio simulation package (VASP) were employed to unveil the electronic structures, encompassing the band structure and density of states (DOS). Photoluminescence (PL) spectroscopy was employed to scrutinize the luminescent properties, while the thermal stability of the PL spectra was also evaluated. The most prominent emission peak, exhibiting an orange-reddish hue, was observed at 601 nm upon excitation at 406 nm. The quenching mechanism of Sm3+ ions within the Sr2LuNbO6 host lattice was identified as a dipole-dipole interaction, with the quenching concentration of 3 at%. Moreover, the phosphors demonstrated excellent thermal stability, with an activation energy (Ea) value of 0.126 eV. These findings collectively underscore the promising potential of Sm3+:Sr2LuNbO6 orange-reddish phosphors for applications in white light-emitting diodes (w-LEDs).

A theoretical study of surface lithium effects on the [111] SiC nanowires as anode materials.

Silicon carbide nanowires (SiCNWs) are considered a promising alternative material for application in lithium-ion batteries, with researchers striving to develop new electrode materials that exhibit high capacity and high charge/discharge rate performance. To gain a deeper understanding of the application of SiCNWs in semiconductor material science and energy supply fields, we investigated the effects of nanoscale and surface lithiation on the electrical and mechanical properties of SiCNWs grown along the [111] direction. First-principles calculation was used to study their geometries, electronic structures, and associated electrochemical properties. Herein, we considered SiCNWs with full hydrogen passivation, full lithium passivation, and mixed passivation at different sizes. The formation energy indicates that the stability of SiCNWs increases with the increasing diameter, and the surface-lithiated SiC nanowires (Li-SiCNWs) are found to be energetically stable. The mixed passivated SiCNWs exhibit the properties of indirect band gap with the increase of lithium atoms on the surface, while the fully lithium passivated nanowires exhibit metallic behavior. Charge analysis shows that a portion of the electrons on the lithium atoms are transferred to the surface atoms of the nanowires and electrons prefer to cluster more near the C atoms. Additionally, Li-SiCNWs still have good mechanical resistance during the lithiation process. The stable open-circuit voltage range and theoretical capacity of these SiCNWs indicate their suitability as anode materials. In this study, Materials Studio 8.0 was used to construct the models of the SiCNWs. And all the density functional theory (DFT) calculations were performed by the Vienna ab initio Simulation Package (VASP). The self-consistent field calculations are performed over a Monkhorst-Pack net of 1 × 1 × 6k-points. The energy convergence criteria for the self-consistent field calculation were set to 10-5eV/atom with a cutoff energy of 400eV.

Initial corrosion behavior of 10CrNi3MoV steel and Q235 steel in marine atmosphere

Exploring the corrosion behavior of materials in a marine atmosphere and studying their corrosion resistance mechanisms can provide a basis for developing new weathering steels. This paper primarily introduces the initial corrosion behavior and corrosion resistance mechanism of 10CrNi3MoV steel in a marine atmosphere and explores the effects of Ni on the corrosion resistance. The corrosion resistance of 10CrNi3MoV steel and Q235 steel was compared using the weight loss method. The results show that the corrosion rate of 10CrNi3MoV steel was approximately half that of Q235 steel. The rust layer morphology and elemental distribution of 10CrNi3MoV steel were observed via scanning electron microscopy and energy-dispersive X-ray spectroscopy. The composition of the rust layer was analyzed using X-ray diffraction and X-ray photoelectron spectroscopy, and the protective effect of the rust layer was further tested using an electrochemical test. The reason why Fe2NiO4 is beneficial for improving the corrosion resistance of the rust layer was explained using the Vienna Ab initio Simulation Package. The results reveal that the morphology, composition, element distribution, and electrochemical properties of 10CrNi3MoV steel were considerably stronger than those of Q235 steel because of the formation of Fe2NiO4 in the rust layer. Fe2NiO4 refines the rust layer particles and promotes the transformation of corrosion products to α-FeOOH. In addition, it imparts ion selectivity to the rust layer, effectively blocking the invasion of Cl−.

A DFT study of the physical properties of novel vanadium-based half-Heusler alloys VYAl (Y = Ni,Pd, and Pt) pertinent to their optoelectronics application

We investigated three novel 18-valence electron count (VEC) vanadium-based half-Heusler alloys, VYAl (Y = Ni, Pd, and Pt), for their structural, mechanical, electronic, and optical properties using density functional theory (DFT). The computation was carried out employing Vienna Ab-initio Simulation Package (VASP) and all three alloys have exhibited structural, chemical, mechanical, and thermodynamic stability. We obtained the lattice constants of 5.520, 5.800, and 5.820 Å for VNiAl, VPdAl, and VPtAl, respectively. The elastic parameters imply a ductile and hard nature of the system and exhibit anisotropic behavior. Electronic band characterization demonstrated that all three alloys are semiconductors with direct narrow gaps at the Γ-point which is crucial for photovoltaic applications. In addition to that, the high density of the band states near the Fermi level indicates a promising candidate for thermoelectric conversion. The influence of SOC interaction in the system generates a small shift in the bands. From the optical response, we infer that the studied compounds have exceptional light absorption and reflection quality, making them suitable for optoelectronics purposes.

Role of outer shell electron-nuclear distant of transition metal atoms (TMA) on band gap reduction and optical properties of TiO2 semiconductor

The reduction of the band gap of titanium dioxide (TiO2) via transition metal atoms (TMAs) is the focus of many research groups to increase its absorption to visible region of electromagnetic (EM) radiation. In this modeling it was shown that atoms having near outer electron shells affect strongly on the band gap of TiO2. The TiO2 has exceptional photoactivity, high stability, and cost-effectiveness. The results of the current study emphasized that adjustable TiO2 photocatalyst material can be produced through band gap reduction by Pt, Pd, and Ni dopants. The electronic configurations and optical properties of both undoped and (Ni, Pd and Pt)-doped TiO2 have been studied using first-principles calculations within the framework of Density Functional Theory (DFT) with the aid of the Vienna Ab initio Simulation Package (VASP). The role of electronegativity of TMAs on band gap drop was discussed for the first time. The band gap of clean TiO2 was found to be 3.2 eV using the band structure (BS) and Tauq model. The results indicate that Ni TMA with lowest electronegativity reduces the band gap of TiO2 to the lowest value (0.86 eV). The results of BS and density of state revealed the fact that small outer shell electron-nuclear distant TMA more affected the band gap of TiO2. The band gap determined from the imaginary part of the optical dielectric function closely aligns with those determined from the BS diagram. The increase in the refractive index (n) was observed with the increase of Ni, Pd, and Pt into the TiO2 structure, which indicates an increase in charge density within the TiO2 structure. The reflectance, absorbance, and transmittance results suggest that Pd and Pt-doped TiO2 are responsive to the visible region of electromagnetic radiation, whereas Ni-doped TiO2 exhibits responsiveness in the IR region. In its pure state; TiO2 was found almost transparent in the visible and IR regions of EM radiation.

Tunable electronic and magnetic properties of defective g-ZnO monolayer doping with non-metallic elements.

The electronic and magnetic properties of non-metallic (NM) elements doping defective graphene-like ZnO (g-ZnO) monolayer including O vacancy (VO) and Zn vacancy (VZn) are studied. The results show that VO-g-ZnO is a semiconductor and VZn-g-ZnO is a magnetic semiconductor. B, C, N, Si, P, 2S, and 2Si doping VO-g-ZnO systems present half-metal and magnetic semiconductors, and the magnetism mainly originates from the spin polarization of doping atoms. For single or double NM elements doping VZn-g-ZnO, 2P doping system presents a semiconductor, while other systems present ferromagnetic metal, half-metal, and magnetic semiconductor. The magnetism of single NM elements doping VZn-g-ZnO mainly comes from the spin polarization of O atoms near the defect point. For double NM elements doping VZn-g-ZnO, spin splitting occurs mainly in p orbitals of O atoms, dopant atoms, and d orbitals of Zn atoms. NM elements doping defect g-ZnO can effectively regulate the electronic and magnetic properties of the system. The software package VASP 5.4.1 (Vienna ab initio Simulation Package) is used for calculations in this paper. The local density approximation (LDA) is adopted as an exchange and correlation function to perform the structural optimization and analysis of electronic structure and magnetic properties.

Pressure effects on the structural, electronic, elastic, optical, and vibrational properties of YMg intermetallic compounds: a first-principles study

The properties of YMg in B2 structure have been comprehensively analysed using the first-principles plane-wave pseudopotential method. Specifically, the structural, electronic, elastic, vibrational, and optical properties were investigated using the generalized gradient approximation (GGA) method in the context of density functional theory. The Vienna ab initio simulation package (VASP) was utilized for these calculations. The computed lattice parameter (3.803 Å) and bulk modulus (41.33 GPa) are consistent with the earlier data on ambient pressure. The electronic band structure and energy-dependent density of states reveal the metallic nature of the titled compounds. The Born stability requirements confirmed the mechanical stability. The analysis of Pugh’s and Poisson’s ratios and Cauchy’s pressure reveals that YMg is ductile under the pressures in consideration. According to several anisotropy indices, the compound is noticeably anisotropic both in ambient and under pressure. Our investigation includes an analysis of several fundamental mechanical parameters of the material, including the bulk modulus, the pressure derivative of the Zener anisotropy factor, Poisson’s ratio, isotropic shear modulus and Young’s modulus with a particular focus on their dependence on pressure. We have determined that the elastic constants obtained remain mechanically stable, satisfying the Born Stability conditions even at high pressures of up to 60 GPa. To explore the dynamic stability of YMg, we analysed the material’s phonon dispersion curves. The examined compound displays stability under dynamic conditions from 0 GPa to 30 GPa, as evidenced by its positive vibration frequencies. However, this stability is not sustained under higher pressure, as the compound becomes unstable after 30 GPa to 70 GPa. The electronic band structure and density of states diagrams demonstrate YMg’s metallic properties. At atmospheric pressure (0 GPa), the total density of states (TDOS) near the Fermi level is approximately 1.63 states/eV, with pressure application reducing DOS. The dielectric function, refractive index, and energy loss spectra are examined within the 0–20 eV energy range. YMg exhibits its highest absorption between 4 and 11 eV. The peak optical conductivity is observed around 0.78 eV (equivalent to 1589.5409 nm), while the most significant energy loss occurs at 11.90 eV, roughly corresponding to 2.8 Hz in the ultraviolet spectrum. Moreover, we extensively analyzed the material’s phonon thermodynamic and optical properties, providing insights into its behavior under various conditions. The outcomes acquired at zero pressure are generally coherent with the current theoretical values.