Using a tight-binding method, the formation energies, diffusivity and localized vibrational frequencies of self-interstitial atoms were calculated for these body-centered-cubic transition metals. As a test of the method, comparisons to experiment were made for the perfect body-centered cubic phonon spectra and to previous ab initio self-interstitial atom formation energies. In addition, vibrational spectra calculated from molecular dynamics via the velocity autocorrelation method were presented. For all of the systems studied, it was found that the localized vibration frequency of a self-interstitial atom dumb-bell pair was roughly twice the frequency of the body-centered cubic phonon density-of-states peak. An Arrhenius temperature dependence was also found for self-interstitial atom hopping, with frequency pre-factors ranging between the cut-off of the ideal body-centered cubic lattice and the highest frequencies of the self-interstitial atom dumb-bell. In all cases, it was found that the energy barrier to self-interstitial atom diffusion was approximately 0.1eV.

Vibrational Modes and Diffusion of Self-Interstitial Atoms in Body-Centered-Cubic Transition Metals: a Tight-Binding Molecular-Dynamics Study. Finkenstadt, D., Bernstein, N., Feldman, J.L., Mehl, M.J., Papaconstantopoulos, D.A.: Physical Review B, 2006, 74[18], 184118