Thermoelastic Properties of Cadmium Fluoride

Abstract

The second-order elastic moduli, as well as their temperature and pressure derivatives, and the thermal expansion of single-crystal Cd${\mathrm{F}}_{2}$ were determined at room temperature. The values of the elastic moduli (in units of ${10}^{11}$ dyn/${\mathrm{cm}}^{2}$) are ${c}_{11}=18.270$, ${c}_{12}=6.674$, and ${c}_{44}=2.175$. The measured values of the temperature derivatives (in units of ${10}^{\ensuremath{-}4}$ ${\mathrm{deg}}^{\ensuremath{-}1}$) are $\frac{d\mathrm{ln}{c}_{11}}{\mathrm{dT}}=\ensuremath{-}3.71$, $\frac{d\mathrm{ln}{c}_{12}}{\mathrm{dT}}=\ensuremath{-}5.08$, and $\frac{d\mathrm{ln}{c}_{44}}{\mathrm{dT}}=\ensuremath{-}5.33$; the pressure derivatives are $\frac{d{c}_{11}}{\mathrm{dP}}=7.11$, $\frac{d{c}_{12}}{\mathrm{dP}}=5.52$, and $\frac{d{c}_{44}}{\mathrm{dP}}=1.35$; the thermal expansion is 2.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$ ${\mathrm{deg}}^{\ensuremath{-}1}$. From the elastic data, a Debye temperature of 328\ifmmode^\circ\else\textdegree\fi{}K was deduced. The experimentally measured values of ${c}_{44}$ and the pressure derivatives were compared with theoretically calculated ones. Good agreement was found for the pressure derivatives, while a large discrepancy for ${c}_{44}$ was noted. The possible reasons for these correlations and the conclusions pertaining to the lattice interactions in Cd${\mathrm{F}}_{2}$ are discussed.