CORRELATION BETWEEN THE ELASTIC SHEAR INSTABILITY MECHANISM AND EMPIRICAL CRITERIA FOR IRRADIATION-INDUCED AMORPHIZATION

In an attempt to correlate the shear instability mechanism with empirical criteria for irradiation-induced amorphization, shear moduli of an A3B-type fcc crystal were calculated as a function of the chemical long range order parameter S using a Morse potential. The shear moduli were found to decrease with decreasing S. When the depth and the curvature of the A-B potential were changed while keeping the A-A and B-B potentials constant, the magnitude of the decrease in shear moduli is greater for deeper and narrower A-B potentials. The present results indicate that a shear instability should occur more readily in compounds with larger ordering energy and larger elastic moduli. These results agree with the reported empirical criteria for irradiation-induced amorphization, therefore providing further support for the shear instability mechanism for solid-state amorphization.