Electronic, electrical and thermodynamic properties of Ca5Si3 by first principles calculations and low temperature experimental techniques

A combined experimental and computational study of the Ca5Si3 phase is presented. Its’ electronic structure and lattice stability are investigated by first principles methods: four different crystal lattices have been investigated by means of density functional theory (DFT) calculations and pseudopotentials within the generalized-gradient approximation using the VASP code. The Ca5Si3 phase is predicted to undergo an high pressure transition: the lattice transition tI32(Cr5B3-type) → tI32(W5Si3-type) has been predicted by DFT to occur at 14.9 GPa. The electronic and band structure of the tI32 Cr5B3-type lattice is calculated and discussed. The Ca5Si3 phase ground state structure is predicted to be a metal with a peaked density of states below the Fermi energy and a sharp minimum right above it. Experimentally the low temperature resistivity and heat capacity of the Ca5Si3 phase have been measured between 2 and 300 K and discussed in view of our computational predictions and available literature. The Ca5Si3 tI32(Cr5B3-type) standard pressure polymorph exhibits a metallic temperature dependence of the electric conductivity in agreement with the DFT predictions.