The specific heat of an anisotropic surface

Abstract

A Green's function method is used to find the low temperature change in the specific heat due to a (110) surface on a simple cubic monatomic lattice. Two separate first neighbor force constant models are used for the calculation: the first assumes that the atomic motion normal to the surface is uncoupled from motion parallel to the surface; the second is the familiar two force constant model popularized by Montroll and Potts. Both models are anistotropic in the surface and neither satisfies the condition of rotational invariance. Analytic expressions are found for the surface mode dispersion relations and for the low temperature specific heat. It is found that for small deviations from isotropy, the change in the specific heat is independent of the model and is the same for the (110) and (100) surfaces.