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Reply To ‘‘Comment On ‘Brillouin-Scattering Study Of The Elastic Constants Of Phenothiazine Through The Phase Transition’ ’’, J. Sartwell, Craig J. Eckhardt
Reply To ‘‘Comment On ‘Brillouin-Scattering Study Of The Elastic Constants Of Phenothiazine Through The Phase Transition’ ’’, J. Sartwell, Craig J. Eckhardt
Craig J. Eckhardt Publications
Disagreement in the ordering of relative magnitudes of the elastic constants of phenothiazine with those of Ecolivet et al. is resolved. Dubious methodologies and assumptions employed by Ecolivet et al. in their measurements, approximations, and arguments [C. Ecolivet et al., Phys. Rev. B 44, 4185 (1991)] are noted. Samples employed by these investigators in both their ultrasonic and Brillouin measurements are shown to exhibit properties consistent with impure samples and inconsistent with those of Sartwell and Eckhardt.
Anisotropic Anharmonicity Of Lattice And Molecular Vibrations Of 1,2,4,5 Tetrabromobenzene Determined By Piezomodulated Raman Spectroscopy, K.M. White, Craig J. Eckhardt
Anisotropic Anharmonicity Of Lattice And Molecular Vibrations Of 1,2,4,5 Tetrabromobenzene Determined By Piezomodulated Raman Spectroscopy, K.M. White, Craig J. Eckhardt
Craig J. Eckhardt Publications
Strain-induced coupling constants for the anharmonicity of Raman-active lattice and certain molecular modes of vibration in 1,2,4,5-tetrabromobenzene (TBB) crystals have been determined using piezomodulated Raman spectroscopy. These constants, which are directly related to the first anharmonic term in the potential energy expansion for lattice dynamical calculations, are a quantitative measurement of the modal anharmonicities in the TBB molecular crystal. Application of uniaxial stress in the experiments permits the anisotropy of the anharmonicity to be determined as well as its magnitude. The TBB lattice modes are significantly coupled by the induced strains and the effects of coupling were observed to be …