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 $\left(R\overline{3}m\right)$ is found to exist up to at least $26\mathrm{GPa}$. From refinements of x-ray diffraction patterns information is derived on changes of $\mathrm{Co}\text{−}\mathrm{O}$ and $\mathrm{Li}\text{−}\mathrm{O}$ 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-Grüneisen 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.