Effect of pressure on the structural properties and Raman modes ofLiCoO2

The high-pressure behavior of fully intercalated lithium cobaltite, ${\mathrm{LiCoO}}_{2}$, has been investigated by angle-dispersive synchrotron x-ray powder diffraction and Raman spectroscopy. The layered structure $(R\overline{3}m)$ is found to exist up to at least $26\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. From refinements of x-ray diffraction patterns information is derived on changes of $\mathrm{Co}\text{\ensuremath{-}}\mathrm{O}$ and $\mathrm{Li}\text{\ensuremath{-}}\mathrm{O}$ bond lengths under pressure. The stability of the ambient-pressure phase is confirmed by Raman spectroscopy. The pressure coefficients for the ${A}_{1\mathrm{g}}$ and ${E}_{\mathrm{g}}$ Raman modes and their mode-Gr\"uneisen parameters are reported as well as qualitative observations concerning unusual changes in width and intensity of the Raman lines under pressure. The obtained high-pressure structural and vibrational properties are compared to results of ab initio calculations.