High pressure Ca-VI phase between 158-180 GPa: Stability, electronic structure and superconductivity

TL;DR

This study uses ab initio calculations to explore the stability, electronic properties, and superconductivity of a new high-pressure Ca-VI phase between 158-180 GPa, revealing its stability and a maximum Tc of about 25K at 172 GPa.

Contribution

It introduces a detailed analysis of the Ca-VI phase's stability, electronic structure, and superconducting properties under high pressure, which was not previously characterized.

Findings

Ca-VI phase is stable between 158-180 GPa.

Superconducting with Tc up to ~25K at 172 GPa.

Charge transfer from 4s to 3d orbitals occurs at maximum Tc.

Abstract

We have performed ab initio calculations for new high-pressure phase of Ca-VI between 158-180 GPa. The study includes elastic parameters of mono- and poly-crystalline aggregates, electronic band structure, lattice dynamics and superconductivity. The calculations show that the orthorhombic Pnma structure is mechanically and dynamically stable in the pressure range studied. The structure is superconducting in the entire pressure range and the calculated Tc (~25K) is maximum at ~172 GPa, where the transfer of charges from 4s to 3d may be thought to be completed.