We propose neutron diffraction experiments on quasicrystals (Ti45Zr38Ni17)1-xDx (x = 0 and 0.58). Ti45Zr38Ni17 absorbs and desorbs hydrogen atoms substantially. However the hydrogen atom sites have been unknown. Therefore, site determination of hydrogen atom is highly required to deeply understand the hydrogen absorption and desorption mechanism. Since qusicrystals do not follow crystallographic symmetry rules, general method like Rietveld refinement cannot be employed. In order to characterize the structures, we will employ the atomic pair distribution function analysis and the Reverse Monte-Carlo method. For the analysis, we would like to obtain diffraction data of the samples collected in the high Q range (~ 50 Å-1) using the GEM (or SANDALS) diffractometer with high intensity and high resolution at the ISIS spallation neutron source.