  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.
