T. Eaton and . Cole, 18 Resolutions are given at elastic scattering and energy ranges are expressed considering the down scattering Stokes side only, i.e., the energy range accessible at the lowest temperature, J. Am. Chem. Soc, vol.86, issue.3157, 1964.

. Bée, Quasielastic Neutron Scattering Adam Hilger and Bristol, 1988.

S. Launois, R. Ravy, and . Moret, 23 http://accelrys.com/products/materials-studio/ 24 http://dirac.cnrs-orleans.fr/plone/software, Phys. Rev. B, vol.52, issue.293, 1995.

H. Schober, A. Itoh, V. Klapproth, W. Chihaia, E. S. Kuhs et al., 42 The Grüneisen parameter j k =? ln j k ln V represents the relative change in the frequency of the oscillator as a function of the volume of the system. For more information on this subject, the lector can refer to N, Ashcroft and N. D. Mermin, Solid State Physics Saunders College, p.25, 1976.