NEUTRON SCATTERING STUDY OF HYDROGEN VIBRATIONS IN POLYCRYSTAL AND GLASSY Ti₂CuH_x

Hydrogen vibration spectra for both polycrystalline Ti 2 CuH 1.03 and amorphous Ti 2 CuH 1.26 have been measured in the energy range of 50–210 meV using a beryllium filter detector spectrometer. From the experimental curves it can be seen that although there is some similarity in vibrational density of states of the hydrogen atoms in these two samples, large differences between them are evident. The optical vibration peak of crystalline sample reveals a narrow frequency distribution with a FWHM of 54 meV and consists apparently 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 structures 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 and there is local fluctuation in its chemical composition.