Specific features of the electronic structure and optical properties of skutterudites LaFe4X12 (XÂ =Â P, As and Sb)

We have reported comprehensive calculation for electronic band structure, density of states, Fermi surface and the optical properties of LaFe4X12 (X = P, As and Sb) compounds. The experimental lattice constant a and the two internal free parameters u and v were optimized by minimizing the total energy using the full potential linear augmented plane wave (FPLAPW + lo) method within the local density approximation (LDA). The experimental atomic positions were optimized using the FPLAPW + lo method within Perdew, Burke and Ernzerhof generalized gradient approximation (PBE-GGA). From the obtained relaxed geometry the electronic band structure, the chemical bonding, electronic charge density and the optical properties have been determined using FPLAPW + lo within the recently modified Becke-Johnson potential (mBJ). It has been found that substituting P → As → Sb show significant influence on the bands/states dispersions. The calculated values of the density of the states at Fermi level N(EF) and the associated electronic specific heat coefficient (γ) are increases with substituting P → As → Sb that is attributed to the fact that below Fermi level (EF) there exists several bands with less dispersion moves close to EF when we substitute P → As → Sb. The bonds nature and the interactions between the atoms were investigated in two crystallographic planes namely (1 0 0) and (1 0 1). The Fermi surface is formed by two bands which are mainly consist of Fe-d states and X-p states. The observed Fermi surface consists of empty areas that represent the holes and shaded areas corresponding to the electrons. The calculated optical properties exhibit that there exists two lossless regions also it shows that the spectral structure shift toward lower energies when we replace P by As and As by Sb.