Plane-wave Pseudopotential Approach Research Articles

Structural, electronic, optical, mechanical, and phononic bulk properties of tetragonal trirutile antimonate MSb2O6 (M = Fe, Co, Ni, or Zn): a first-principles prediction for optoelectronic applications

Abstract This work does an extensive analysis of the optoelectronic and mechanical properties of the tri rutile structure type 3d transition metal Antimonate MSb2O6 (M = Fe, Co, Ni, or Zn), for the first time, utilizing the pseudo-potential plane wave approach within the density functional theory framework. When calculating the structural, optical, and mechanical properties, the exchange-correlation interactions were studied using the GGA-PBE functional, whereas when computing electronic, it is analyzed using the HSE06 hybrid functional. The equilibrium lattice parameters exhibit good agreement with the available experimental results. The electronic properties were estimated using the GGA-PBE and HSE06 functionals. Based on the calculated electronic properties with the GGA-PBE functional, the FeSb2O6, CoSb2O6, and NiSb2O6 materials exhibit metallic behavior with energy gap values of 0 eV, while ZnSb2O6 is a semiconductor with a narrow direct band gap (Γ-Γ) of 0.5 eV. Furthermore, the computed band gaps using the HSE06 functional are 0 eV, 0 eV, 1 eV (Γ-Γ), and 4 eV (Γ-Γ) for FeSb2O6, CoSb2O6, NiSb2O6, and ZnSb2O6, respectively. Density of states diagrams were used to gain deeper insights into the characteristics of the energy bands. The optical properties of these compounds, such as the dielectric function, energy loss function, conductivity, reflectivity, refractive index, and absorption coefficient were investigated over the energy range of 0 to 40 eV. The materials exhibited a high absorption coefficient and a significantly low reflectivity within the UV-Vis energy spectrum. The negative cohesive energy Ecoh implies the chemical (thermodynamic) stability of the trirutile MSb2O6 (M = Fe, Co, Ni, or Zn). Mechanical stability is confirmed by applying the Born stability criteria using elastic constants (Cij). The absence of imaginary frequencies in the phonon spectrum calculations confirms the dynamic stability of the studied compounds. These results are consistent with previous experimental research on these materials in photocatalysis and gas sensor applications. On the other hand, these compounds possess exceptional high and broad optical absorption UV range, making them suitable for use in next-generation ultraviolet photodetectors.

Study of the fundamental physical characteristics of the Zintl phase K2BaCdSb2

The structural, elastic, thermodynamic, electronic, and thermoelectric characteristics of K2BaCdSb2 were investigated utilizing ab initio methods. The structural, elastic, and thermodynamic properties were calculated using the pseudopotential plane wave approach with the GGA-PBEsol exchange-correlation functional. The computed equilibrium structural characteristics closely match the available data. The anticipated elastic constants reveal that K2BaCdSb2 is mechanically stable, brittle, and exhibits significant elastic anisotropy. The full potential linearized augmented plane wave approach with the Tran-Blaha modified Becke-Johnson potential was used to determine the electronic structure of K2BaCdSb2.It is found that K2BaCdSb2 is a semiconductor with a Γ-Γ type direct bandgap of 0.85 eV. Bonding analysis shows the bond between Cd and Sb atoms within the [CdSb2]4− polyanion is of covalent nature and that between the K/Ba atom and the [CdSb2]4− polyanion is of ionic character. The thermoelectric characteristics of K2BaCdSb2 were analyzed at a temperature of 500 K for of charge-carrier concentrations from 1 × 1018 to 3 × 1020 cm−3.When the concentration of holes is 1.0 × 1020 cm−3, The power factor reaches a value of 17 × 1010 W m−1 K−2.s−1 for a hole concentration of 1.0 × 1020 cm−3. For the p-doped K2BaCdSb2 with a concentration of 1.0 × 1018cm−3, the electronic figure of merit is 0.95.

Pressure effect investigation of structural, electronic, elastic and magnetic properties of X2CrSb (X = Mn, Co and Cu) Heusler alloys

Using the plane-wave pseudo-potential approach and generalized-gradient approximation for the exchange–correlation effects in the framework of the density functional theory, the structural, electronic, elastic and magnetic properties of X2CrSb ( ▪ and Cu) Heusler alloys were investigated. For ▪ , a structural phase-transition from XA to L21-phase is expected at 8.933GPa. This compound exhibits half-metallic behavior before becoming a magnetic metal at 17.5GPa. The ▪ is a half-metal under expansion and nearly half-metal above 1GPa. The total magnetic moments for ▪ , ▪ and ▪ are respectively equal to 5.0μB, 1.0μB and 3.4μB, and are mainly localized on Cr except for ▪ in XA-phase where the magnetic moment is localized on Mn. The DOS analysis shows weak spin-polarizations for ▪ and a higher polarization under expansion for ▪ and ▪ . Under compression, the polarization is weakened in ▪ , it remains at a high level before it vanishes at 29.4μB in ▪ .

Efficient exact exchange using Wannier functions and other related developments in planewave-pseudopotential implementation of RT-TDDFT.

The plane-wave pseudopotential (PW-PP) formalism is widely used for the first-principles electronic structure calculation of extended periodic systems. The PW-PP approach has also been adapted for real-time time-dependent density functional theory (RT-TDDFT) to investigate time-dependent electronic dynamical phenomena. In this work, we detail recent advances in the PW-PP formalism for RT-TDDFT, particularly how maximally localized Wannier functions (MLWFs) are used to accelerate simulations using the exact exchange. We also discuss several related developments, including an anti-Hermitian correction for the time-dependent MLWFs (TD-MLWFs) when a time-dependent electric field is applied, the refinement procedure for TD-MLWFs, comparison of the velocity and length gauge approaches for applying an electric field, and elimination of long-range electrostatic interaction, as well as usage of a complex absorbing potential for modeling isolated systems when using the PW-PP formalism.

A comprehensive first-principles investigation of structural, electronic, vibrational, optical, thermodynamic and thermoelectric properties of LiZnAs

The structural, electronic, vibrational, optical, thermodynamic and thermoelectric properties of Nowotny–Juza filled tetrahedral semiconductor LiZnAs under high pressure is investigated using the plane-wave pseudo-potential approach in the frame work of density functional theory (DFT) within the generalized gradient approximation (GGA). The calculated lattice constant (a0) and bulk modulus (B0) at ambient pressure are consistent with earlier reported experiment and theoretical results. The variation in Lattice constant, Bulk modulus (B0), Young modulus (Y), Shear modulus (G), Elastic anisotropy factor (A), Poission ratio (μ), Paugh (B/G) ratio and Elastic constants with pressure is analyzed and concluded. Electronic band structure calculations reveal that with applied pressure direct band gap increases and the indirect band gap decreases. Thermodynamic properties reveals thermodynamically stability with pressurize conditions. The real and imaginary parts of the Dielectric function (ε), Refractive index (η), Extinction Coefficient (k), Optical Conductivity (s), Electron/Optical Energy Loss Function (L), Absorption Coefficient (α), Reflectivity (R) at different pressure conditions are correspondingly studied. With applied pressure the absorption spectra shows a blue shift which makes LiZnAs as potential candidates for the application of optoelectronic devices in ultraviolet frequency range. The thermoelectric properties like Seebeck coefficient (S), Electrical conductivity (σ), and Electronic thermal conductivity (k) and Power factor (PF) have been studied as a function of temperature and chemical potential. Positive value of calculated Seebeck coefficient with temperatures ensures the p-type semiconducting nature of LiZnAs. Results provides theoretical guidance for future experimental investigations and industrial applications of LiZnAs.

Electronic structure and delithiation mechanism of vanadium and nickel doped Li2MnPO4F cathode material for lithium-ion batteries

This study calculates the energy band structure and density of states of Lithium manganese fluorophosphate (Li2MnPO4F, a lithium transition metal phosphate compounds) using the first-principles plane-wave pseudopotential approach within the density-functional theory. The model of Li2M0.5Mn0.5PO4F (M = V, Ni) with transition metal doped Mn sites is constructed by using the CASTEP module. The calculation findings indicate that the transition metal doping can regulate the energy band structure of the intrinsic system, and Li2MnPO4F makes the band gap decrease, and the volume increase with the Li ions of being deintercalated, and the electrons can be readily stimulated from the valence band to the conduction band. The findings indicate that Li2MnPO4F is a favorable cathode material for high-voltage lithium ion batteries (LIBs). The introduction of vanadium (V) and nickel (Ni) doping reduces the band gap, facilitating an easier excitation of electrons from the valence band to the conduction band. This study provides a theoretical study of new cathode materials for high performance LIBs.

Computational investigation of the structural, elastic, electronic, and thermodynamic properties of chloroperovskites GaXCl3 (X = Be, Ca, or Sr) using DFT framework

In this study, we employed the pseudopotential plane wave approach to examine the influence of the X atom (X = Be, Ca, or Sr) on the physical properties of isostructural chloroperovskites GaXCl3. The GGA-PBEsol functional was employed to simulate the exchange–correlation interactions. The computed equilibrium lattice parameters exhibit a high level of concordance with the existing theoretical findings. The cohesion energy and enthalpy of formation were computed to verify the energetic stability of the materials under consideration. The determined values of the single-crystal elastic constants (Cij) indicate that GaBeCl3 remains mechanically stable up to a hydrostatic pressure of 18 GPa. Similarly, GaCaCl3 preserves its stability up to 5 GPa, while GaSrCl3 remains mechanically stable up to 1.25 GPa. The projected Cij values were used to estimate several elastic moduli and related properties, including the shear and bulk moduli, sound wave speeds, Young’s modulus, Poisson’s ratio, and Debye temperature. The energy band structures of the studied compounds, as predicted by the HSE06 functional, demonstrate their wide bandgap semiconductor nature. Specifically, GaBeCl3 demonstrates an indirect bandgap of 3.828 eV, while GaCaCl3 reveals an indirect bandgap of 4.612 eV and GaSrCl3 has an indirect bandgap of 4.405 eV. The quasiharmonic Debye approach was employed to examine various thermal parameters, including the temperature dependence of the unit cell volume, bulk modulus, expansion coefficient, Debye temperature, isochoric and isobar heat capacities, Grüneisen parameter, and entropy function. It has been shown that GaBeCl3 demonstrates a lower thermal expansion coefficient and a higher Debye temperature in comparison to GaCaCl3 and GaSrCl3.

Bending deformation modulation of the optoelectronic properties of molybdenum ditelluride doped with nonmetallic atoms X (X = B, C, N, O): a first-principles study.

A first-principles approach based on density functional theory was used to explore the effect of bending deformation on the electrical structure of molybdenum ditelluride doped with nonmetallic atoms X (X = B, C, N, and O). The study included alternate doping of nonmetallic atoms, as well as a comparison of the effects of intrinsic bending deformation and nonmetallic doping deformation. The results demonstrate that boron atom doping raises the Fermi energy level. Examining the energy band structure indicates that the intrinsic molybdenum ditelluride is a direct band gap semiconductor, which is transformed from a direct band gap to an indirect band gap after doping. We selected boron-doped systems for bending deformation and compared them with the intrinsic systems. With increasing deformation, all systems start to shift from semiconductor to metal. When the deformation reaches 8°, the energy levels fill and the electron energy increases. The intrinsically bent systems transition from direct band gap to indirect band gap and eventually to metal. The indirect band gap semiconductor-to-metal transition process occurs after the bending deformation of the boron-doped atoms. The analytical results show that the absorption and reflection peaks of the molybdenum ditelluride system are blue-shifted after the bending deformation of the boron-doped atoms. Under fundamental principles, this research depends on the density functional theory framework (DFT) using the CASTEP module in the Materials-Studio software. The plane-wave pseudopotential approach with modified gradient approximation and the Perdew-Burke-Ernzerhof (PBE) generalized function is used for structure optimization and total energy calculations of the X-doped (X = B, C, N, O) MoTe2 system at different shape variables. Geometry optimization of the 27-atom superlattice MoTe2 was carried out, followed by alternative doping of tellurium atoms in the molybdenum ditelluride with B, C, N, and O. In this paper, the intrinsic bending deformation and B-doping of molybdenum ditelluride were selected for deformation analysis. Intrinsic bending deformations and boron-doped molybdenum ditelluride with bending angles ranging from 2° to 8° were employed for deformation investigation. In Fig.1, pink is used to represent doped B atoms, orange is used to describe Te atoms, and green is used to represent Mo atoms. For the degree of deformation of molybdenum ditelluride, in this paper, it is expressed by the bending angle, i.e., the angle of the plane of molybdenum ditelluride after bending and deformation of a single layer of molybdenum ditelluride concerning the angle of the plane folded for the deformed plane. How to do it: For ease of presentation, the atomic chains are set to different colors. The purple part on both sides of the figure is bent and deformed, 3-5 atoms are fixed appropriately, and the middle part is deformed. On this basis, the bending deformation of intrinsically doped and boron-doped MoTe2 is comparatively analyzed. The effect of boron-doped atoms on the structure of MoTe2 is systematically investigated to study its structural stability and electronic structure. Fig.1 a1 and a2 The main and side views of intrinsic MoTe2; b1 and (b2) the main and side views of MoTe2 doped with boron atoms bent by 8°.

Electronic, Elastic, Optical, and Thermodynamic Properties Study of Ytterbium Chalcogenides Using Density Functional Theory

In this study, the structural, electronic, optical, elastic, and thermodynamic properties of Ytterbium chalcogenides YbX (X = S, Se and Te) were computed within the first principles using generalized gradient approximation (GGA) as implemented in the pseudopotential plane wave approach. The equilibrium total energy for YbX (X = S, Se, and Te) was calculated as a function of the energy cutoff, k-point grid, and lattice parameter. An optimized lattice parameter of 5.6, 5.66, and 6.136 Å were calculated for YbS, YbSe, and YbTe, respectively. The energy band gaps of YbS, YbSe, and YbTe computed are 1.14, 1.32, and 1.48 eV, respectively. In addition, the low band gap (less than 3 eV) for ytterbium chalcogenides indicated that they may have potential applications in photovoltaic cells and laser diodes. Moreover, the negative dielectric function value for a certain frequency range indicates that these compounds are suitable for specific optical and microwave circuit applications. The result of elastic and thermodynamic property computation reveals that ytterbium chalcogenides are mechanically and thermodynamically stable, which can be useful in a variety of electronic device applications.

First-principles study of the effects of doping B, N, and O on the photoelectric properties of Cr adsorbed GaS.

To lessen the impact of the dangerous metal Cr, this paper applies the first principles to investigate the adsorption behavior and photoelectric properties of GaS on Cr. The effects of doped GaS on Cr adsorption behavior are investigated with four GaS systems, which are pure, boron (B)-doped, nitrogen (N)-doped, and oxygen (O)-doped, in order to maximize the characteristics of GaS for use in novel sectors, to obtain understanding of the impact of doping on the electronic structure and optical properties of GaS adsorption of Cr, as well as to promote the development of the material. Four GaS adsorbed Cr systems, pure, B-doped, N-doped, and O-doped, are optimized, and the optimized results show that the stable adsorption position of Cr on both pure and doped GaS is the top position of Ga atoms, whereas doped elements B, N, and O can promote the adsorption of Cr on GaS, and the order of the strength of this promotion is B > N > O. In this paper, molecular simulation calculations and analyses using the CASTEP module in the software Materials Studio are performed to simulate the structure optimization of GaS-adsorbed Cr materials doped with B, N, and O atoms by using the generalized gradient approximation (GGA) plane-wave pseudopotential approach [1] and the Perdew-Burke-Ernzerhof (PBE) generalized function [2]. From the convergence test, it is reasonable to set the K-point network to 4 × 4 × 1 and the truncation energy to 500eV [3]. In this paper, a 3 × 3 × 1 supercell structure with 18 S atoms and 18Ga atoms is selected. The convergence value of the iterative accuracy is 1.0e - 5eV/atom, and all the atomic forces are less than 0.02eV/Å. A vacuum layer of 16Å is also set in the C direction to avoid interlayer interactions of GaS. First, we optimize the geometry of the model and then analyze the nature of the adsorption energy and electronic structure corresponding to the model.

First-principles analysis of the structural, thermodynamic, elastic and thermoelectric properties of LuXCo2Sb2 (X = V, Nb and Ta) double half Heusler alloys

We used the pseudopotential plane wave approach, as implemented in the Quantum Espresso program, to investigate the impact of X atoms (V, Nb, and Ta) on the physical properties of LuXCo2Sb2 double half Heusler alloys. We determined the equilibrium structural parameters, including the crystal lattice parameters, atomic position coordinates, and bulk modulus, with and without including the spin-orbit effects. The predicted single-crystal elastic constants (Cij) show that the title compounds are mechanically stable with a pronounced elastic anisotropy. The bulk modulus, shear modulus, Young's modulus, Poisson coefficient, Debye temperature, and Vickers hardness coefficient were deduced from Cij via the Voigt-Reuss-Hill approximations. We also determined the variations of some macroscopic physical parameters as functions of temperature and pressure, namely the thermal expansion coefficient, lattice thermal conductivity, heat capacity at constant volume, Debye temperature and entropy. The considered alloys demonstrate special thermal properties under pressure and heat conditions, specifically, their low thermal expansion coefficient and lattice thermal conductivity; their thermal expansion coefficient is lower than 4.5 × 10−5 K−1 at 1000 K, and lattice thermal conductivity don’t exceed 1 W.m−1 K−1 for temperatures higher than 300 K. Furthermore, we investigated the temperature and charge carrier concentration dependencies of some thermoelectric coefficients. The results of this study reveal the potential of the considered compounds for achieving a figure of merit greater than 0.5 at a temperature of 500 K and a doping concentration of 1020 cm−3.

B-doping on the electronic structure and photocatalytic properties of g-C3N4/Janus PtSSe heterojunctions: A first-principles study

The effect of B doping on the stability, electronic structure, work function, and optical properties of g-C3N4/Janus PtSSe heterojunctions has been investigated based on the density-functional theory plane-wave ultrasoft pseudopotential approach. It is shown that the binding energy of g-C3N4/PtSSe after B doping is negative and has a low layer spacing and lattice mismatch rate. It is stable at a room temperature of 300 K, proving its structural and thermodynamic stability. B-atom doping of g-C3N4/SPtSe and g-C3N4/SePtS heterojunctions leads to the upward shift of the Fermi energy level resulting in a significant reduction of the band gap and significant orbital hybridization. The impurity band near the Fermi energy level easily transfers electrons from the valence band into the conduction band, which makes electron leaps easier. Different built-in electric fields are formed when the g-C3N4 and Se(S) atomic layers are in contact. The reduction of the bandgap after B doping enables the photogenerated electron-hole pairs between the heterojunction interfaces to be better separated under the action of the built-in electric field, which reduces the composite rate of the electron-hole pairs and greatly improves the carrier migration and photocatalytic performance. The absorption and reflection coefficients of g-C3N4/SPtSe-BNC and g-C3N4/SePtS-BNC are the highest and decrease slowly in the visible region, which indicates that they have the optimal photocatalytic performance, and they can effectively broaden the range of light absorption and promote the utilization of light. The introduction of the B–B bonding effectively improves the photocatalytic activity of the heterojunction.

Pressure-induced metallization in the absence of a structural transition in the layered transition-metal dichalcogenide ZrSe2.

First-principles calculations were carried out on the ZrSe2 compound, which has been of interest owing to its technologically important physical properties. The structural, electronic and optical properties of this compound were investigated under pressure through the plane wave pseudopotential approach within the framework of density functional theory. A comparison between the computed crystal structure parameters and the corresponding experimental counterparts shows a very good agreement between them. Fitting the pressure-volume data using the third-order Birch-Murnaghan equation of state yielded a bulk modulus B0 = 38.17 GPa and a pressure derivative of bulk modulus B'0 = 8.2 for hexagonal ZrSe2. The relationship between the band structure and pressure is revealed. We calculated the total density of state (TDOS) under different pressures and partial density of state (PDOS) from 0 to 10 GPa. According to our calculations, metallization of hexagonal ZrSe2 is predicted to occur at around 10 GPa and pressure-induced band-gap engineering reveals the transformation of the indirect to direct band gap with increasing pressure. Furthermore, optical properties, such as the complex dielectric function, refractive index and reflectivity spectra of this compound, were studied for incident electromagnetic waves in an energy range up to 45 eV. The contributions to various transition peaks in the optical spectra are analyzed and discussed with the help of the energy-dependent imaginary part of the dielectric function.

Stochastic and mixed density functional theory within the projector augmented wave formalism for simulation of warm dense matter.

Stochastic density functional theory (DFT) and mixed stochastic-deterministic DFT are burgeoning approaches for the calculation of the equationof state and transport properties in materials under extreme conditions. In the intermediate warm dense matter regime, a state between correlated condensed matter and kinetic plasma, electrons can range from being highly localized around nuclei to delocalized over the whole simulation cell. The plane-wave basis pseudopotential approach is thus the typical tool of choice for modeling such systems at the DFT level. Unfortunately, stochastic DFT methods scale as the square of the maximum plane-wave energy in this basis. To reduce the effect of this scaling and improve the overall description of the electrons within the pseudopotential approximation, we present stochastic and mixed DFT approaches developed and implemented within the projector augmented wave formalism. We compare results between the different DFT approaches for both single-point and molecular dynamics trajectories and present calculations of self-diffusion coefficients of solid density carbon from 1 to 50eV.

Structural, electronic, optical and vibrational properties of CdSiP2 from first-principles

We report the results of a first-principles research of the structural, electronic, linear and nonlinear responses, and vibrational properties of CdSiP2 based on the density functional theory using pseudopotential plane-wave approach. We calculate the energy band structure, dielectric function, absorption coefficient, reflectivity, refractive index, SHG susceptibility, and phonon dispersion curves. In order to obtain accurate band gap value of CdSiP2, the GW approximation method is used to calculate the quasiparticle band structure and the corrected band gap value is in excellent agreement with experimental measurements. Furthermore, the corrected band gap can be used as scissor shift for linear and nonlinear optical properties calculations. The linear-response theory is used to derive the phonon dispersion curves and density of states. All zone-center phonon modes are calculated and LO-TO splitting of the infrared modes are identified. The results show a good agreement with available experimental data and other calculations.

Structural, elastic, and thermodynamic properties of BaXCl3 (X = Li, Na) perovskites under pressure effect: ab initio exploration

In this study, we employed the ab initio pseudopotential plane wave approach, utilizing the GGA-PBEsol exchange-correlation functional, to investigate the structural, elastic, and thermodynamic properties of BaXCl3 (X = Li, Na) perovskites under hydrostatic pressures ranging from 0 to 18 GPa. Apart from utilizing the GGA-PBEsol functional, this study also employed the GGA-PBE, GGA-WC, and LDA functionals to simulate the exchange-correlation interactions for computing the structural parameters. Our results show that the optimized lattice parameters are in good agreement with previously predicted values. Based on the calculated elastic moduli of a single crystal, we found that both BaLiCl3 and BaNaCl3 perovskites retain mechanical stability under hydrostatic pressures of up to 18 GPa. Furthermore, we calculated several other important parameters that describe the polycrystalline aggregates of these compounds, including the modulus of compressibility, the shear modulus, the Poisson’s ratio, Young’s modulus, the speeds of sound, and the Debye temperature. Additionally, we examined the temperature and pressure dependencies of the thermal coefficients of the perovskites using the quasi-harmonic approximation. Notably, all of the results presented in this study are reported for the first time and require further confirmation through experimental investigations. We hope that our findings contribute to a more comprehensive understanding of the structural and thermodynamic properties of BaXCl3 (X = Li, Na) perovskites under pressure.

Electronic and magnetic properties of Half Heusler alloy NiCrSi

Utilizing the Quantum Espresso Package and the plane wave pseudopotential approach, the electrical and magnetic characteristics of the Half Heusler alloy NiCrSi have been investigated.Ultrasoft pseudo-potential is used for this calculation. Through our calculation, it was revealed that NiCrSi is a half-metallic ferromagnet in nature with a bandgap of 0.81eV and an effective moment of 2µB respectively. The origin of the gap is mainly due to the covalent band gap and d-d band gap in the system separating bonding states from anti-bonding states. Our calculation predicts a larger spin moment at Cr site than at Ni site which is antiparallel to the moment of Si. The hybridization of Ni- 3d and Cr-4d states can open a minority spin gap at Ef resulting in the semi-conducting nature of the minority spin band.

Structural, vibrational, electronic, thermodynamic and thermoelectric properties of CaCdSi Half Heusler compound: A first-principles study

The new half-Heusler CaCdSi alloy, as a new crucial nonmagnetic thermoelectric candidate, is desired to be understood in terms of its potential physical properties and stability in both experimental and theoretical studies. Here we investigate the thermal properties of half-Heusler CaCdSi using the plane-wave pseudopotential approach based on the density functional theory within the generalized gradient approximation (GGA). Firstly, dynamical and mechanical stability was assured in its cubic phase. These results also elucidate the stable and brittle nature of the compound. Furthermore, electronic band structure calculation shows that the CaCdSi alloy has semiconductor behavior with a direct band gap of 0.59 eV. Lastly, the Seebeck coefficient, electronic conductivity, electronic thermal conductivity, the power factor, and figure of merit have been investigated using the semi-classical Boltzmann transport theory. The high value of ZT of the CaCdSi alloy makes it a potential candidate material for thermoelectric applications. Our research not only enriches the family of thermoelectric materials but also provides a good platform for further experimental investigations.

Structural, Electronic, Mechanical, and Thermodynamic Properties of Na Deintercalation from Olivine NaMnPO4: First-Principles Study.

The impact of Na atom deintercalation on olivine NaMnPO4 was investigated in a first-principle study for prospective use as cathode materials in Na-ion batteries. Within the generalized gradient approximation functional with Hubbard (U) correction, we used the plane-wave pseudopotential approach. The calculated equilibrium lattice constants are within 5% of the experimental data. The difference in equilibrium cell volumes for all deintercalated phases was only 6%, showing that NaMPO4 is structurally more stable. The predicted voltage window was found to be between 3.997 and 3.848 V. The Na1MnPO4 and MnPO4 structures are likely to be semiconductors, but the Na0.75MnPO4, Na0.5MnPO4, and Na0.25MnPO4 structures are likely to be metallic. Furthermore, all independent elastic constants for NaxMPO4 structures were shown to meet the mechanical stability requirement of the orthorhombic lattice system.

Structural properties of NaBeH3 material: Ab-initio calculations

Ab-initio calculations from first principle methods were performed toinvestigate the structural properties of perovskite-type hydride NaBeH3material. The pseudopotential plane-wave approach in the framework ofdensity functional theory (DFT) as implemented in the ABINIT codecomputer was used. The exchange-correlation functional for all elementsof our material of interest was described with the local densityapproximation (LDA). Our results of the equilibrium lattice parameter, thebulk modulus, and the pressure derivative of the bulk modulus of cubicNaBeH3 semiconducting material were found at around 3.335 Å (3.339Å), 65.64 GPa and 3.56, respectively. Our data are in good agreementwith the available theoretical data of the literature. In addition, the meltingpoint of our material of interest was calculated and found equal to 1217.45K. To the best of the authors' knowledge, no data is available in theliterature on the melting point of NaBeH 3 material.