R.K. Thapa

Ground state calculation of the electronic structure and magnetic properties of Co2VAl: a local spin density approximation with exchange correlation potential study

We performed first-principles calculations of Co2VAl to determine its electronic and magnetic properties. For this, the density functional-based full potential linearized augmented plane wave method is used. Firstly, volume optimization is done based on generalized gradient approximation to determine the equilibrium lattice parameters. To determine the impact of on-site Coulomb repulsion (U) on the electronic structure, local spin density approximation with exchange correlation potential is used. The U values are varied within reasonable limits to study the resulting effect on the physical properties of the Co2VAl system. The calculated density of states and band structure show that half-metallicity of Co2VAl depends upon the increase in U values. This study concludes that U is sensitive to the type of systems and one should not merely choose the U value randomly.

Study of the enhanced electronic and thermoelectric (TE) properties of ZrxHf1−x−yTayNiSn: a first principles study

A density functional theory (DFT) approach employing generalized gradient approximation (GGA) and the modified Becke Johnson (TB-mBJ) potential has been used to study the electronic and thermoelectric (TE) properties of ZrxHf1−x−yTayNiSn. The presence of an indirect band gap at EF in the parent compound predicts this material to be a small band gap insulator. The substitution of Ta atoms at the Hf site increases the density of states (DOS) at EF which facilitates charge carrier mobility. The influence of Ta content increases the Seebeck coefficient and electrical conductivity, and suppresses the thermal conductivity; as a result the figure of merit ZT is enhanced. We report an increment in ZT value of 36% over the undoped system. The theoretical data were compared with the experimental results.

A DFT study of BeX (X = S, Se, Te) semiconductor: modified Becke Johnson (mBJ) potential

The electronic, optical and elastic properties of BeX were performed within full potential liberalized augmented plane wave method based on density functional theory (DFT). Generalized gradient approximation (GGA) and modified Becke Johnson (TB-mBJ) potential were used for exchange correlation. The mBJ gives improved band gap as compare to GGA and in close agreement with the experimental results. The present band gaps of BeS, BeSe and BeTe calculated within mBJ are 4.40, 4.0 and 2.40 eV respectively.

Electronic, optical and thermoelectric properties of PrMO3 (M = Al, Ga, In) from first-principles calculations

We have systematically investigated the electronic structure, optical properties, Born effective charges and the thermoelectric properties of PrMO3 (M = Al, Ga, In) compounds using first-principles density functional theory calculations. Two different density functional approaches, the full potential linearized augmented plane wave method (FP-LAPW) and the plane wave pseudo potential method were used for the present study. A direct band gap at a Γ point of 3.8 eV, 3.07 eV and 2.9 eV is observed for PrAlO3 (PAO), PrGaO3 (PGO) and PrInO3 (PIO). The optical anisotropy of PAO and PGO is revealed from the computed optical properties such as complex dielectric function, refractive index, and absorption coefficient whereas PIO is found to be optically isotropic in the low energy range making it suitable for use in the development of ceramic scintillators. The inter-band transitions to the optical properties are analyzed with the help of calculated band structures. The Born effective charge and the static dielectric tensor of these materials have also been calculated.

Electronic and magnetic properties of a full-Heusler alloy Co2CrGe: a first-principles study

The structural, electronic, and magnetic properties of Co2CrGe, a Heusler alloy, have been evaluated by first-principles density functional theory and compared with the known experimental and theoretical results. Generalized gradient approximation is used for structural study, whereas local spin density approximation is used for electronic calculation. First-principles structure optimizations were done through total energy calculations at 0 K using the full-potential linearized augmented plane wave method as implemented in the WIEN2K code.

First principles phase transition, elastic properties and electronic structure calculations for cadmium telluride under induced pressure: density functional theory, LDA, GGA and modified Becke–Johnson potential

We report first principles phase transition, elastic properties and electronic structure for cadmium telluride (CdTe) under induced pressure in the light of density functional theory using the local density approximation (LDA), generalised gradient approximation (GGA) and modified Becke–Johnson (mBJ) potential. The structural phase transition of CdTe from a zinc blende (ZB) to a rock salt (RS) structure within the LDA calculation is 2.2 GPa while that within GGA is found to be at 4 GPa pressure with a volume collapse of 20.9%. The elastic constants and parameters (Zener anisotropy factor, Shear modulus, Poissons ratio, Youngs modulus, Kleinmann parameter and Debyes temperature) of CdTe at different pressures of both the phases have been calculated. The band diagram of the CdTe ZB structure shows a direct band gap of 1.46 eV as predicted by mBJ calculation which gives better results in close agreement with experimental results as compared to LDA and GGA. An increase in the band gap of the CdTe ZB phase is predicted under induced pressure while the metallic nature is retained in the CdTe RS phase.