HIGH-PRESSURE ACOUSTIC-WAVE VELOCITIES AND EQUATIONS OF STATE OF THE ALKALI CHLORIDES

Acoustic wave velocities have been measured in RbCl and CsCl to 17 GPa. The compressional wave velocities vary with density as V(P) (km/s) = 3.4143(84) + 1.368 (11) DELTArho for the high-pressure phase of RbCl and V(P) (km/s) = 2.8247 (57) + 1.1469 (77) DELTArho for CsCl (numbers in parentheses indicate uncertainties on the last digit). The equations of state of RbCl and CsCl have also been determined at room temperature to approximately 30 GPa. Eulerian finite strain equation of state parameters are rho02 = 3.3068 (10) Mg m-3, K(0T) = 17.9 (10) GPa and K(0T)' = 5.23 (29) for RbCl in the B2 structure, and K(0T) = 17.01 (29) GPa and K(0T') = 5.49 (15) for CsCl. The accumulated set of data for the alkali chlorides under high pressure is used to test several empirical relations between velocity and density. A simple logarithmic relation is shown to allow the most accurate extrapolation from low-pressure velocity data. Gruneisen's parameters are also calculated from the velocity and density data, allowing a complete thermal equation of state tp be developed for the alkali chlorides.