Electronic and optical properties of HoNi₅ and HoNi₄Si: An LSDA + U study

Abstract

We investigated the effect of Si substitution on structural, electronic and optical properties of [Formula: see text]-type [Formula: see text] alloys. The optimized lattice constants and internal cell parameters are in agreement with the available data. We found that the valence band is mainly dominated by Ni-3d states in the energy range 0–4 eV below the [Formula: see text], whereas conduction band is contributed by spin-down Ho-[Formula: see text] states and lies about 2 eV above the [Formula: see text]. Substitution of Si atoms for Ni decreases the total magnetic moment from 6.308 [Formula: see text]/f.u. [Formula: see text] to 4.052 [Formula: see text]/f.u. [Formula: see text], whereas magnetic moments on [Formula: see text]-ions increase from 3.92 [Formula: see text]/atom [Formula: see text] to 4 [Formula: see text]/atom [Formula: see text]. On the other hand, induced moment on Ni[Formula: see text]-ions decrease rapidly to a negligibly small value. By the use of charge density estimates, we found that Ho-5d, Ni-3d and Si-3p orbitals are mainly involved in bonding and there is a weak hybridization between Ni-3d and Si-3p orbitals which varies with substitution of Si for Ni. Furthermore, the complex role played by Ho-[Formula: see text] electrons is also investigated, they are found to be partly involved in metallic bondings as well as in the intra-atomic charge transfer from [Formula: see text] to [Formula: see text] states in [Formula: see text]-ions. The calculated interband optical conductivity spectra reproduce the main features of experimental spectra well and also reveal their metallic nature.