Effect of pressure on the Raman modes of antimony

TL;DR

This study investigates how pressure affects the Raman-active phonon modes of antimony, revealing mode softening, broadening, and anharmonic effects, supported by experimental Raman spectroscopy and ab initio calculations.

Contribution

It provides new insights into pressure-induced phonon behavior and anharmonicity in antimony's A7 phase through combined experimental and theoretical analysis.

Findings

Raman modes soften with increasing pressure.

Significant broadening of Raman peaks under pressure.

Strong anharmonicity observed in calculations.

Abstract

The effect of pressure on the zone-center optical phonon modes of antimony in the A7 structure has been investigated by Raman spectroscopy. The A_g and E_g frequencies exhibit a pronounced softening with increasing pressure, the effect being related to a gradual suppression of the Peierls-like distortion of the A7 phase relative to a cubic primitive lattice. Also, both Raman modes broaden significantly under pressure. Spectra taken at low temperature indicate that the broadening is at least partly caused by phonon-phonon interactions. We also report results of ab initio frozen-phonon calculations of the A_g and E_g mode frequencies. Presence of strong anharmonicity is clearly apparent in calculated total energy versus atom displacement relations. Pronounced nonlinearities in the force versus displacement relations are observed. Structural instabilities of the Sb-A7 phase are briefly addressed in the Appendix.