Pressure induced phase transitions in TiH2
Abstract
Recent room temperature experiments on TiH2 [Kalita, J. Appl. Phys. 108, 043511 (2010)], an important compound in hydrogen storage research, revealed a cubic (fcc, Fm-3m) to tetragonal (bct, I4/mmm) phase transition at around 0.6 GPa, which was suggested to remain stable up to at least 90 GPa. However, the simulated X-ray diffraction (XRD) pattern of the I4/mmm structure cannot explain all the diffraction peaks observed at 90 GPa. In this article, we apply the recently developed particle swarm optimization algorithm for crystal structure prediction to propose that at 63 GPa TiH2 presents a further phase transition from I4/mmm to P4/nmm, which we have also confirmed is dynamically and enthalpically stable up to 294 GPa. Moreover, the XRD patterns and calculated lattice parameters of the P4/nmm structure are in good agreement with the experimental available data. Above 294 GPa, we predict a monoclinic P21/m structure to be stable. © 2013 American Institute of Physics. ; We acknowledge funding supports from the National Natural Science Foundation of China (under Grant Nos. 91022029 and 11025418), the research fund of Key Laboratory of Surface Physics and Chemistry (No. SPC201103), and the China 973 Program under Grant No. 2011CB808200. A.B. acknowledges the Department of Education, Universities and Research of the Basque Government, UPV/EHU (Grant No. IT-366-07) and the Spanish Ministry of Science and Innovation (Grant No. FIS2010-19609-C02-00). ; Peer Reviewed
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