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

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. - Highlights: • The equilibrium structural parameters and elastic constants of Ba₈Si₄₆ are calculated. • Elastic stability criterion suggests the formation of lattice vacancies under high pressure. • Endohedral Ba atoms can modulate the mechanical and electronic properties. • Pressure causes a shrinkage of the superconducting temperature. • Pressure driven electronic s-d transfer behavior are observed.