In ZrBe2H0.56 above 500K, Be planes were separated by hexagonal Zr planes in the AlB2 structure with the H atoms occupying interstitial sites that form a honeycomb net in the Zr planes. The data from quasi-elastic neutron scattering using two spectrometers covering a wide range of resolutions from 1 to 64μeV could be fitted with a simple model using only 2 parameters for all momentum transfers at each temperature. The parameters were an elastic-like fraction and the hopping rate associated with a quasi-elastic contribution described by 2-dimensional nearest-neighbor uncorrelated hopping among the partially occupied interstitial sites. The temperature dependence of the hopping rate follows an Arrhenius relation with an activation enthalpy of 0.30eV.

Quasi-Elastic Neutron Scattering Study of Diffusive Hydrogen Motion in ZrBe2H0.56. R.L.Cappelletti, Z.Chowdhuri, T.J.Udovic, R.M.Dimeo, B.C.Hauback, A.J.Maeland: Physical Review B, 2006, 73[22], 224109 (9pp)