Influence of missing guest and host atoms on the mechanical and electronic properties of type-I clathrate compound Ba8Si46

Abstract

We presented a theoretical study of the structural, mechanical and electronic properties of type-I silicon clathrate Ba8Si46 under high pressure through first principles methods. The calculated results show an obvious increase of the crystal compressibility due to the pressure induced lattice vacancies formed by missing host silicon atoms, which is supposed to account for the sudden volume collapse during the compress in experiments. Adjusting the occupied configuration of endohedral guest barium atoms can modulate the tensile, shear, hardness and brittle properties of Ba8Si46 crystal considerably. Moreover, both the pressure and intrinsic vacancy are found to weaken the strong peak of electronic density of states at Fermi level which yields a shrinkage of superconducting temperature of Ba8Si46.