Surface Mean-Square Amplitudes of Vibration for NaCl

Abstract

The mean-square amplitudes and mean-square velocities of vibration have been calculated for the (100) surface of NaCl with the Kellermann rigid-ion model. The calculated value of $\frac{{〈u_z^2〉}_{\mathrm{surface}}}{{〈u_z^2〉}_{\mathrm{bulk}}}$ (the $z$ direction being perpendicular to the surface) is only about 1.6 at high temperatures, as compared with calculated and experimental values ranging upward from about 2.0 for monatomic metals and noble-gas solids.