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Computer Simulation of Structural Stability by Hydrogenation in Hydrogen Storage Materials

Published online by Cambridge University Press:  15 March 2011

Masahiko Katagiri ,
Hidehiro Onodera  and
Hiroshi Ogawa
Masahiko Katagiri
Affiliation:
National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
Hidehiro Onodera
Affiliation:
National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
Hiroshi Ogawa
Affiliation:
National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
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Abstract

Microscopic mechanism of Hydrogen-Induced Amorphization (HIA) in AB2 C15 Laves phase compound is studied. Experimentally, compounds in which A atoms are contracted and B atoms are expanded in Laves phase show HIA. It suggests that the relative atomic size is the controlling factor. We investigate the role of the size effect by molecular Dynamics (MD) methods using Lennard-Jones pair-wise potentials. Our simulations show that in such a compound, the bulk modulus is remarkably reduced by hydrogenation compared to the isotropic tensile load, so that elastic instability is facilitated. This situation is caused by the negative increase of the pressure-fluctuation contribution in the elastic constant. The relaxation of B-atom positions by hydrogenation gives the fluctuation contribution. The fluctuation effect is essential in the elastic instability, although the energy change is small.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1127: Symposium T – Mobile Energy , 2008 , 1127-T05-10
Copyright
Copyright © Materials Research Society 2009

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References

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