NEUTRON SCATTERING STUDY OF HYDROGEN VIBRATIONS IN POLYCRYSTAL AND GLASSY Ti_2CuH_x

Neutron vibrational spectra for both amorphous Ti_2CuH_(1.26) and polycrystalline Ti_2CuH_(1.03) are measured in the energy range of 50-210 meV with a beryllium filter detector spectrometer. From the experimental curve it can be seen that although there is somewhat similarity in vibrational density of statesof the hydrogen atoms in these two samples, large differences between them are evident. The optical vi-bration peak of crystalline sample reveals a narrow frequency distribution with a FWHM of 54 meVand apparently consists of two peaks at 92 and 147 meV. In the amorphous sample the optical peak occurs at nearly the same frequency as the main peak of the former but with strongly increased width (～104 meV FWHM). The result shows that on the average, the H--sites occupied in amorphous and crystalline structure are mainly tetrahedral type holes, but the distribution of local environment for the hydrogen atoms in the alloy glass is much broader because the polyhedra in it may be heavily distorted andthere is local fluctuation in its chemical composition.