Ultrasonic parameters in the born model of the rubidium halides

Abstract

Values of all dC dP have been obtained at 295°K and are strikingly smooth when plotted against nearest neighbour distance, d 0. When combined with known temperature coefficients of the elastic constants, they lead to values of ξ=dln B T / dT) v which are uniformly −1 × 10 −4 deg −1 for these crystals with low Debye temperature. The resulting Born model exponential parameters, d 0 ρ , are precisely linear with d 0, in contrast with d 0 ρ values where compression ξ were used in the necessary correction for vibrational effects. Values of dB T dP are uniformly 5.6, a general magnitude well accounted for by the Born model which, however, predicts a significant systematic variation in the four halides. In all these features the Rb halides are similar to the Na and K halides.