Disorder effects on heat transport properties of orientationally disordered crystals

6 págs.; 3 figs.; 2 tabs. ; PACS number s : 65.60. a, 66.70. f, 61.43. j, 63.50. xThe thermal conductivity k(T) of the orientational glass state of 1,2-difluoro-1,1,2,2-tetrachloroethane (CFCl2-CFCl2, Freon 112) and cyanocyclohexane (C6H11CN) has been measured under equilibrium pressure within the temperature range 2-100 K. The results show that the soft-potential model is able to account for low-temperature data and, indeed, quantitative agreement of all data considered is found within this realm. The details beyond such temperatures are heavily dependent on chemical details and a large plateau is observed for Freon 112 which is rationalized in terms of resonant scattering of phonons by simple oscillators. Such a view is given additional support by the presence of a strong low-frequency feature in the generalized frequency spectrum of the former material as proven by inelastic neutron-scattering spectroscopy. ©2010 The American Physical SocietyThis work was financially supported in part by the Spanish Ministry of Science and Innovation Grants No. FIS2008-00837 and No. MAT2007- 65711-C-4-01 and the Catalan Government Grant No. 2009SGR-1251 and joint projects of NAS of Ukraine and the Russian Foundation for Fundamental Research Grant No. N 9-2009.Peer Reviewe