[1] Kitagawa I, Terao K, Aoki M and Yamada H 1997 J.
Phys.: Condens. Matter 9 231

[2] Cuevas F, Joubert J M, Latroche M and Percheron-Gu\'{egan
A 2001 Appl. Phys. A 72 225

[3] Dehouche Z, Grimard N, Laurencelle F, Goyette J and Bose T
K 2005 J. Alloys Compd. 399 224

[4] Willers E, Wanner M and Groll M 1999 J. Alloys Compd.
293--295 915

[5] Park J G, Jang K J, Lee P S and Lee J Y 2001 Int. J.
Hydrogen Energy 26 701

[6] Mendelssohn M H, Geuwn D M and Dwight A E 1997
Nature 45 269

[7] Joubert J M, Latroche M, \v{Crn\'{y R, Bowman R C Jr,
Percheron-Gu\'{egan A and Yvon K 1999 J. Alloys. Compd.
293 124

[8] Du H L, Zhang W Y, Wang C S, Yang J Z and Chen B 2003
Solid State Commun. 128 157

[9] Atteberry J E, Agosta D S, Nattrass C E, Leisure R G,
Jacob I, Rowman R C Jr and Yeheskel O 2004 J. Alloys Compd.
376 139

[10] Blanco M A, Francisco E and Lua\v{na V 2004 Comput.
Phys. Commun. 158 57

[11] Segall M D, Lindan Philip J D, Probert M J, Pickard C J,
Hasnip P J, Clark S J and Payne M C 2002 J. Phys.: Condens.
Matter 14 2717

[12] Perdew J P, Burke K and Ernzerhof M 1996 Phys. Rev.
Lett. 77 3865

[13] Monkhorst H J and Pack J D 1976 Phys. Rev. B
13 5188

[14] Segall M D, Lindan P J D, Probert M J, Pickard C J,
Hasnip P J, Clark S J and Payne M C 2002 J. Phys.: Condens.
Matter 14 2717

[15] Murnaghan F D 1944 Proc. Natl. Acad. Sci. U.S.A.
30 244

[16] Maradudin A A, Montroll E W, Weiss G H and Ipatova I P
1971 Theory of Lattice Dynamics in the Harmonic Approximation
(New York: Academic)

[17] Francisco E, Recio J M and Blanco M A 2001 Phys.
Rev. B 63 094107

[18] Fl\'{orez M, Recio J M, Francisco E, Blanco M A and
Mart\'{\in Pend\'{as A 2002 Phys. Rev. B 66 144112

[19] Blanco M A, Pend\'{as A M, Francisco E, Recio J M and
Franco R 1996 J. Mol. Struct. (Theochem.) 368 245

[20] Fl\'{orez M, Recio J M, Francisco E, Blanco M A and
Pend\'{as A M 2002 Phys. Rev. B 66 144112

[21] Francisco E, Recio J M, Blanco M A and Mart\'{\in
Pend\'{as A 1998 J. Phys. Chem. 102 1595

[22] Francisco E and Sanjurjo M A 2001 Phys. Rev. B
63 094107

[23] Joubert J M, \v{Cern\'{y R, Latroche M,
Percheron-Gu\'{egan A, Yvon K 2005 Intermetallics 13
227

[24] Angel R J 2001 EOSFIT6.0 Users Guide, {http://www.
crystal.vt.edu/crystal/software/manual60.pdf

[25] Bereznitsky M, Ode A, Hightower J E, Yeheskel O, Jacob I
and Leisure R G 2002 J. Appl. Phys. 91 5010