Electronic topological transitions in Nb$_3$X (X = Al, Ga, In, Ge and Sn) under compression investigated by first principles calculations

TL;DR

This study uses first principles calculations to investigate electronic topological transitions in Nb3X compounds under pressure, revealing changes in Fermi surface topology that align with experimental anomalies.

Contribution

It provides the first detailed computational analysis of pressure-induced electronic topological transitions in Nb3X compounds, confirming experimental observations.

Findings

Electronic topological transitions occur at specific pressures in Nb3Al and Nb3Ga.

Fermi surface topology changes are correlated with elastic constant anomalies.

Mechanical stability is maintained under high pressure in all compounds.

Abstract

First principles electronic structure calculations of A-15 type Nb$_3$X (X = Al, Ga, In, Ge and Sn) compounds are performed at ambient and high pressures. Mechanical stability is confirmed in all the compounds both at ambient as well as under compression from the calculated elastic constants. We have observed four holes and two electron Fermi surfaces (FS) for all the compounds studied and FS nesting feature is observed at M and along X - $\Gamma$ in all the compounds. A continuous change in the FS topology is observed under pressure in all the compounds which is also reflected in the calculated elastic constants and density of states under pressure indicating the Electronic topological transitions (ETT). The ETT observed at around 21.5 GPa, 17.5 GPa in Nb$_3$Al and Nb$_3$Ga are in good agreement with the anomalies observed by the experiments.