A LATTICE-GAS MODEL FOR THE ZENER RELAXATION

The Zener relaxation is an anelastic relaxation process in disordered crystals due to stress-induced changes of atomic order. We present a m odel calculation of this process for a simple cubic lattice gas which is non-interacting except for the exclusion of multiple occupancies. T he relaxation results from the stress-induced formation and dissolutio n of bonds between (paired) lattice gas atoms on nearest-neighbour sit es. Relaxation spectra are obtained for the compressibility s(11) + 2s (12) and the shear compliance s(11) - s(12). The spectra are proportio nal to c(2)(1 - c)(2) where c is the occupation probability of a given site. The frequency dependence of the spectra is determined by the ju mp rate of the lattice gas atoms. Compared with a spectrum for a singl e relaxation time, the spectrum of s(11) - s(12) is moderately broaden ed, whereas the spectrum of s(11) + 2s(12) shows a sizable broadening. The present results are applicable to both interstitial and substitut ional alloys.