Enhanced lattice specific heat due to gold impurities in Cu-Au alloys

Abstract

A study of the effects of force constant changes and lattice expansion on the lattice specific heat has been made in dilute copper-gold alloys. A defect perturbation model which includes the change in the mass at the impurity site and the changes in the impurity-host crystal interactions around the impurity have been considered. The lattice expansion caused by the impurity atoms has also been accounted for in the two experimentally studied Cu-Au alloys (2.4 and 4.8 at.% Au). The calculated results compare well with the recent experimental results. The present values of the defect parameters are seen to be similar to those obtained earlier in the study of the phonon frequency shifts and widths of the same system. The defect model, thus, explains the phonon frequencies and phonon widths as well as their average effects seen in the lattice specific heat of these alloys.