The positron lifetime measurements were carried out to confirm the hydrogen interaction process with compound. It was found that positron lifetime of compound hydride increased in comparison to the parent compound and it is suggested that the interaction of hydrogen with compound obeyed the anionic model. The rate of hydrogen desorption for material MmNi(4.5)Al(0.5) increases with number of cycles. The residual gas analysis shows that hydrogen releases with all isotopes or satellites (m(3), m(4) and m(5)) in third cycle of desorption at pressure 10(-7) torr. The X-ray diffraction pattern shows that most of the peaks of a structure were found to be rhombohedral and resembled a bunsenite mineral structure. However, few peaks of material were satisfied by mixed phase of hexagonal and cubic with rhombohedral structure. The rhombohedral phase was the most suitable structure for hydrogen absorption and desorption process. The X-ray fluorescence of material shows the different peaks of misch metal (Mm = Ce, Nd, Pr with background peaks) and Ni peaks but Al and La peaks do not appear. These peaks could not be detected by the detector as these peaks were found in the lower energy region of the spectrum. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.