Calculation of the isotope effect at the interstitials diffusion in crystals by the heating method

The impurity mass dependence of the diffusion coefficient $D(m)$ was investigated by the heating method (reduced version of molecular dynamics method). It is shown that $D(m)$ has a minimum near $m\sim M$ region ($M$ is the mass of a lattice atom), if the impurity interacts with the crystal by short- range potential. The dependence $D(m)$ is monotoneous (without the extremums) for long-range potential but $D(m)$ differs from prediction of the rates theory $D(m)\sim m^{-0,5}$.