Martensitic phase transition from cubic to tetragonal V3Si: an electronic structure study

Abstract

In this study we focus on the subtle changes which occur in the electronic structure and in the Fermi surface topology with the low temperature (21.3 K) cubic → tetragonal martensitic phase transition in V3Si. From the calculations it has been verified the occurrence of a charge transfer from V atoms to Si atoms, with the phase transition to a tetragonal variant of the A-15 structure. The orbital population of s- and p-states of V atoms in the 2e and 4k sites of the tetragonal phase are practically the same. Major differences are seen in the occupation of d-states. There is a decrease in the average electronic energy with the structural transition, which occurs as a result of the emptying of V d-states (mostly from bands 19–20), and these electrons enter preferentially into the Si p-orbitals. The present results thus indicate that the electronic features of the martensitic transition of V3Si, besides being intimately related to the splitting of the Γ12 into the Γ1+ and Γ3+ states and the position of the Γ1+ state relatively to EF, is mainly associated with the gain in the average electronic energy which occurs from an electron transfer from V-d → Si-p states. This is the main source to explain the stability of the tetragonal phase formed at low temperature in this system.