Effect of filled Gd on structural, elastiC and electronic properties of skutterudite structure (TP3; T = Fe, Ru or Os) compounds: A first principles study

We studied the effect of filled Gd on the structural, elastic and electronic properties of binary skutterudite structure TP3 compounds where T = Fe, Ru or Os. All the calculations were performed with the full potential linearized augmented plane wave method as used in the WIEN2k program package. The exchange-correlation potential was solved with use of the generalized gradient approximation (GGA). Volume optimization was done by three different GGA approaches. Among them, the lattice constants obtained with the PBEsol-GGA agreed well with the experimental results. Filled Gd in ternary skutterudite caused an increase in the volume as well as the bulk modulus of each compound. The calculated elastic constants show that these compounds are mechanically stable but FeP3 is brittle and RuP3 and OsP3 are ductile. Filling of Gd in binary skutterudite structure compounds makes all the ternary skutterudite structure compounds brittle. Inclusion of the Hubbard parameter (U) along with the GGA has an insignificant effect on the band structure as well as the magnetic moment. Theoretical values of the elastic parameters of GdFe4P12 and GdRu4P12 are reported for the first time but there are no experimental data available for comparison; thus, these results can be tested by experimentalists and other researchers.