Computer modeling experiments on tetrahedral interstitial‐kink interactions with a special reference to induced Snoek peak

摘要

The energy dissipation per cycle due to the harmonic rigid motion of geometric kinks (built‐in) in the atmosphere of light interstitials which are hopping between tetrahedral sites is investigated analytically as well as numerically in terms of discrete Fourier k space plus Laplace transformation technique. In the linear response case a discrete Debye‐type relaxation spectrum with six distinct branches is found to represent the anelastic behavior of the system uniquely (the nearest neighbor jumps only) and exactly. It is shown by extensive computer modeling experiments that the induced and dislocation embedded kink‐enhanced Snoek peak is composed of six subpeaks, one acoustic and five optical in character. The acoustic part and the optical modes, especially the upper band which is composed of optical modes 6 and 5, are strongly and selectively associated with the isotropic (Cottrell Atmosphere) and the pure shear part (Snoek Cloud) of the elastic dipole tensor of the tetrahedral interstitials, respectively. An extremely accurate and concise analytical expression is deduced which shows that the decoupling procedure of Snoek and Cottrell atmospheres is a reliable approximation.