Ultrasonic and Brillouin scattering measurements of the elastic constants of SrFCl

The six elastic constants of BaFCl which is a crystal of the matlockite family have been measured using ultrasonic and Brillouin scattering techniques. The values obtained are compared with those of BaF2 crystals which exhibit some structural similarities with BaFCl. Because of the layer structure of BaFCl, the 'transverse' elastic constants C66, C44, C12 and C13 and the 'longitudinal' elastic constants C33 and C11 are smaller than the corresponding constants of BaF2. The linear and volume compressibilities are deduced from these measurements. An elastic Debye temperature is calculated ( Theta el=246.5 K) and compared with other experimental (calorimetric) and theoretical (shell model) determinations. Finally, the effect of the dipole moments of the halide ions on the elastic constants for materials of the matlockite family is discussed.

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