Hydrogen movement in cubic Mg₂NiH₄

The motion of hydrogen atoms in Mg₂NiH₄ is studied based on ab initio total-energy calculations using the full potential linearized augmented plane-wave method. We calculate the jump frequency for two kind of rotations of the NiH₄ complex through classical rate theory. The obtained jump frequencies are 4 × 10¹³e^-1.29eV/kT S^-1 and 3 × 1O¹³e-^0.67eV/kT s^-1 for in-plane and out-of-plane rotations, respectively. These values agree well with experimental data as concluded from solving the equation for the linewidth within the Bloembergen-Purcell-Pound theory of nuclear magnetic resonance.