High pressure behavior of CsC8 graphite intercalation compound

TL;DR

This study explores the high pressure phase diagram of CsC8 graphite intercalation compound up to 32 GPa, revealing multiple phase transitions and structural changes involving the Cs sub-network and electronic structure modifications.

Contribution

First comprehensive investigation of CsC8 under high pressure combining multiple spectroscopic and diffraction techniques, identifying new phase transitions and structural mechanisms.

Findings

Phase transitions at ~2.0, 4.8, and 8 GPa

Structural re-arrangement in Cs sub-network

Electronic structure modifications near 8 GPa

Abstract

The high pressure phase diagram of CsC8 graphite intercalated compound has been investigated at ambient temperature up to 32 GPa. Combining X-ray and neutron diffraction, Raman and X- ray absorption spectroscopies, we report for the first time that CsC8, when pressurized, undergoes phase transitions around 2.0, 4.8 and 8 GPa. Possible candidate lattice structures and the transition mechanism involved are proposed. We show that the observed transitions involve the structural re- arrangement in the Cs sub-network while the distance between the graphitic layers is continuously reduced at least up to 8.9 GPa. Around 8 GPa, important modifications of signatures of the electronic structure measured by Raman and X-ray absorption spectroscopies evidence the onset of a new transition.