The low-temperature thermal expansion and Gruneisen parameters of some tetrahedrally bonded solids

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Abstract
The results of thermal expansion measurements using a three-terminal capacitance dilatometer on Ge, GaAs, ZnS, ZnSe and CdTe below 30K and on ZnSe and CdTe between 57 and 90K are reported. Respective values of 0.49, 0.32, -0.14, 0.0 and -0.85 derived for gamma 0 th, the zero temperature limit of the Gruneisen parameter gamma =3 alpha VBs/Cp are given. These are in good agreement with the values of gamma 0 el calculated from the pressure dependence of the elastic constants. gamma (T) as a function of reduced temperature, T/ theta 0, where theta 0 is the Debye temperature determined at the zero temperature limit, is found to have an essentially universal form and passes through a negative minimum at T approximately 0.06 theta 0. The implications of this observation and the importance of the degree of ionicity in dictating gamma 0 are discussed.

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