Motivated by recent experimental work, we use first-principles density functional theory methods to conduct an extensive search for low enthalpy structures of C6Ca under pressure. As well as a range of buckled structures, which are energetically competitive over an intermediate range of pressures, we show that the high pressure system (≳18 GPa) is unstable towards the formation of a novel class of layered structures, with the most stable compound involving carbon sheets containing five- and eight-membered rings. As well as discussing the energetics of the different classes of low enthalpy structures, we comment on the electronic structure of the high pressure compound and its implications for superconductivity.
@article{arxiv.cond-mat/0611511,
title = {Graphite intercalation compounds under pressure},
author = {Gabor Csanyi and Chris J. Pickard and B. D. Simons and R. J. Needs},
journal= {arXiv preprint arXiv:cond-mat/0611511},
year = {2007}
}