Contributions of vibrational dynamics to the local and excess thermodynamic properties ofCu3Ausurfaces

Abstract

In a comparative study of the local and excess thermodynamic properties of ordered (100), (110), and (111) surfaces of ${\mathrm{Cu}}_{3}\mathrm{Au}$ using interaction potentials from the embedded atom method, and a real space Green's function method for the calculation of the local vibrational density of states, we find surface effects to be most pronounced on (110). The enhancement of the low frequency modes resulting from the softening of intralayer force constants causes a remarkable lowering of the vibrational free energy on (110). On ${\mathrm{Cu}}_{3}\mathrm{Au}(100)$ the stiffening of interlayer force constants leads to the appearance of modes above the bulk band that reduce the effect of the enhancement of low frequency modes. Atoms on all three surfaces display characteristics that are distinct from those in the bulk.