The Structure of Barium in the hcp Phase Under High Pressure

TL;DR

This paper investigates the structural changes of barium's hcp phases under high pressure using electronic structure calculations, revealing electronic and core effects influencing lattice parameter variations.

Contribution

It introduces a detailed theoretical analysis of barium's high-pressure hcp phases using LMTO and GPT methods, highlighting electronic transfer effects and core repulsion impacts.

Findings

Drop in c/a ratio linked to electronic instability in phase II

Core repulsion stabilizes structure at very high pressure

Electronic structure calculations explain lattice parameter variations

Abstract

Recent experimental results on two hcp phases of barium under high pressure show interesting variation of the lattice parameters. They are here interpreted in terms of electronic structure calculation by using the LMTO method and generalized pseudopotential theory (GPT) with a NFE-TBB approach. In phase II the dramatic drop in c/a is an instability analogous to that in the group II metals but with the transfer of s to d electrons playing a crucial role in Ba. Meanwhile in phase V, the instability decrease a lot due to the core repulsion at very high pressure. PACS numbers: 62.50+p, 61.66Bi, 71.15.Ap, 71.15Hx, 71.15La