Skutterudites under pressure: An ab initio study

Abstract

Ab initio results on the band structure, density of states, and Fermi surface (FS) properties of LaRu4X12 (X = P, As, Sb) are presented at ambient pressure as well as under compression. The analysis of density of states reveals the major contribution at the Fermi level to be mainly from the Ru-d and X-p states. We have a complicated Fermi surface with both electron and hole characters for all the three compounds which is derived mainly from the Ru-d and X-p states. There is also a simpler FS with hole character derived from the P-pz orbital for LaRu4P12 and Ru-dz2 orbital in the case of As and Sb containing compounds. More interestingly, Fermi surface nesting feature is observed only in the case of the LaRu4P12. Under compression, we observe the topology of the complicated FS sheet of LaRu4As12 to change around V/V0 = 0.85, leading to a behaviour similar to that of a multiband superconductor, and in addition, we have two more hole pockets centered around Γ at V/V0 = 0.8 for the same compound. Apart from this, we find the hole pocket to vanish at V/V0 = 0.8 in the case of LaRu4Sb12 and the opening of the complicated FS sheet gets reduced. The de Haas van Alphen calculation shows the number of extremal orbits in the complicated sheet to change in As and Sb containing compounds under compression, where we also observe the FS topology to change.