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Bonding nature as well as structural, optoelectronic and thermal properties of the cubic XMg₂O₄(X = Si, Ge) spinel compounds have been calculated using a full-potential augmented plane-wave plus local orbitals (FP-APW+lo) method within the density functional theory. The exchange-correlation potential was treated with the PBE-GGA approximation to calculate the total energy. Moreover, the modified Becke–Johnson potential (TB-mBJ) was also applied to improve the electronic band structure calculations. The computed ground-state parameters (a, B, B′ and u) are in excellent agreements with the available theoretical data. Calculations of the electronic band structure and bonding properties show that these compounds have a direct energy band gap (Γ-Γ) with a dominated ionic character and the TB-mBJ approximation yields larger fundamental band gaps compared to those obtained using the PBE-GGA. Optical properties such as the complex dielectric function ε(ω), reflectivity R(ω) and energy loss function L(ω), for incident photon energy up to 40 eV, have been predicted. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the effects of pressure P and temperature T on the thermal expansion coefficient, Debye temperature and heat capacity for the considered compounds are investigated for the first time.

Structural, elastic, electronic and optical properties as well as chemical bonding of the binary alkali metal selenides M₂ Se (M = Li, Na, K, Rb) were calculated using the full potential linearized augmented plane method. From the elastic constants it is inferred that these compounds are brittle in nature. The results of the electronic band structure show that Na₂Se has a direct energy band gap (Γ-Γ), Li₂Se has an indirect energy band gap (Γ- X), while K₂Se and Rb₂Se have an indirect energy band gap (X-Γ). Analysis of the charge distribution plots reveals a dominated ionic bonding in the herein studied compounds. Additionally, we have calculated the optical properties, namely, the real and the imaginary parts of the dielectric function, refractive index, extinction coefficient, optical conductivity and reflectivity for radiation up to 30.0 eV. All these compounds have direct energy band gap greater than 3.1 eV suggesting their use for manufacturing high frequency devices.

The electronic structure, mechanical and thermodynamic properties of Fe₂VX, (with X = Al and Ga), have been studied self consistently by employing state-of-the-art full-potential linearized approach of augmented plane wave plus local orbitals (FP-LAPW + lo) method. The exchange-correlation potential is treated with the local density and generalized gradient approximations (LDA and GGA). Our predicted ground state properties such as lattice constants, bulk modulus and elastic constants appear more accurate when we employed the GGA rather than the LDA, and these results are in very good agreement with the available experimental and theoretical data. Further, thermodynamic properties of Fe₂VAl and Fe₂VGa are predicted with pressure and temperature in the ranges of 0–40 GPa and 0–1500 K using the quasi-harmonic Debye model. We have obtained successfully the variations of the heat capacities, primitive cell volume and volume expansion coefficient.

The ${\mathrm{\text{Cu}}}_2{\mathrm{\text{ZnSnS}}}_4$, ${\mathrm{\text{Cu}}}_2{\mathrm{\text{ZnSnSe}}}_4$ and ${\mathrm{\text{Cu}}}_2{\mathrm{\text{ZnSnTe}}}_4$ and their alloys have been frequently investigated experimentally owing to their suitable bandgap for the solar cell applications. For the first time, density functional theory is applied to explore the structural, electronic and optical properties of ${\mathrm{\text{Cu}}}_2\mathrm{\text{ZnSn}}({\mathrm{\text{S}}}_{1-x}{\mathrm{\text{Te}}}_x)$ and ${\mathrm{\text{Cu}}}_2\mathrm{\text{ZnSn}}({\mathrm{\text{Se}}}_{1-x}{\mathrm{\text{Te}}}_x)$$(x=0,0.25,0.5,0.75,1)$. The energy minimization procedure reveals that the Kesterite phase is stable compared to the Stannite structure. Lattice constants of the compounds are in good agreement with the previous experimental results. The alloys have direct bandgaps which decrease by increasing the concentration of Te. The chemical bonding among the cations and anion is dominantly covalent. Electronic bandgap dependent optical properties like absorption coefficient and optical conductivity are studied in detail. The materials show strong response in the visible region of energy spectrum indicating the usefulness of these materials for optoelectronic devices.

We report the structural, electronic, optical, and thermoelectric properties of the five cubic alkali-earth transition-metals AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) using density functional theory. Structural properties, electronic structures and optical behaviors are calculated explicitly via highly accurate contemporary full potential-linearized augmented plane wave (FP-LAPW) method. The investigated ground state data of these materials is quite close to the experimental information. The modified Becke–Johnson (mBJ) predicts the intermetallic nature of AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) materials. The complex dielectric function of these intermetallic compounds has been calculated and the observed noticeable peaks are examined through mBJ. With the help of complex dielectric function, the other important optical parameters like reflectivities, conductivities and refractive indices of AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) have been calculated as a function of energy. The optical response suggests that AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) compounds can be used for the optoelectronic devices. Further, the thermoelectric properties have been calculated through BoltzTraP program, the calculated values for different thermoelectric parameters recommend that these AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) materials are the suitable candidates for thermoelectric applications.

We have examined the magnetic stability; antiferromagnetic (AFM) ordering; electronic and magnetic properties of composition XMn₂Y₂ (X = Ca, Sr; Y = Sb, Bi) using framework of full-potential linearized augmented plane wave (FP-LAPW) method within generalized gradient (PBE-GGA) approximations in AFM phase. We have specified that AFM state is most suitable for these compounds as compared to other configurations at their relaxed lattice parameters. An AFM spin configuration of Mn atoms is shown to be impressive state for these compounds. Based on its electronic properties, these compounds have a metallic nature in Paramagnetic (PM) but in AFM phase it shows different nature from PM phase. From a suitable phase, it has been cleared that both Mn atoms well-adjusted antiferromagnetically.

We hereby are reporting the transition pressure at which lithium fluoride (LiF) compound transforms from direct band gap to indirect band gap insulator on the basis of FP-LAPW calculations. The fundamental band gap of LiF compound suffers direct to indirect transition at a pressure of 70 GPa. The study of the pressure effect on the optical properties e.g. dielectric function, reflectivity, refractive index and optical conductivity of LiF in the pressure between 0–100 GPa, shows that this pressure range is very critical for LiF compound as there are significant changes in the optical properties of this compound.

In this paper, we have carried out a theoretical investigation on the structural and optoelectronic properties of NaCl under pressure effect via first principle calculations within the density functional theory. The structural phase transition from NaCl(B1) to CsCl(B2)-type structures is determined. The compound has a very wide bandgap in both phases. Optical properties including the absorption coefficient, optical conductivity and frequency dependent reflectivity are explained to characterize the optical nature of NaCl up to pressure of 134 GPa.