6533b853fe1ef96bd12aca68

RESEARCH PRODUCT

Vibrational properties of delafossiteCuGaO2at ambient and high pressures

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In this paper we investigate the vibrational properties of $\mathrm{Cu}\mathrm{Ga}{\mathrm{O}}_{2}$ delafossite by means of Raman experiments and ab initio calculations. Both investigations have been performed at ambient pressure and also at high pressure. The two Raman-active modes have frequencies ${w}_{{E}_{g}}=368\ifmmode\pm\else\textpm\fi{}1\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ and ${w}_{{A}_{1g}}=729\ifmmode\pm\else\textpm\fi{}1\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, and pressure coefficients $2.78\ifmmode\pm\else\textpm\fi{}0.03\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}∕\mathrm{GPa}$ $({E}_{g})$ and $4.64\ifmmode\pm\else\textpm\fi{}0.09\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}∕\mathrm{GPa}$ $({A}_{1g})$. Raman experiments indicate the existence of a phase transition beginning at $26\ifmmode\pm\else\textpm\fi{}1\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. At about the same pressure, ab initio calculations show the presence of a dynamical instability, possibly related to the phase transition. The phonon dispersion curves are also discussed.