By using a tight-binding molecular-dynamics method, calculations were made of the formation energies, diffusivity and localized vibrational frequencies of self-interstitial atoms in these body-centered-cubic transition metals. As a test of these methods, comparisons were made with experiment for perfect body-centered cubic phonon spectra and with previous ab initio self-interstitial atom formation energies. In addition, vibrational spectra calculated from molecular dynamics using 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 of self-interstitial atom hopping was also found; with frequency pre-factors ranging from the cut-off of the ideal body-centered cubic lattice to 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. D.Finkenstadt, N.Bernstein, J.L.Feldman, M.J.Mehl, D.A.Papaconstantopoulos: Physical Review B, 2006, 74[18], 184118