Lattice Dynamics of Biphenyl

This paper presents calculations of the lattice dynamics of a biphenyl crystal, using the “6-exp” potential function. It was noted that an “atom-atom” potential after Kitaigorodskii parameters describes properties of the crystal better than the potential after Poltev and Sukhorukov parameters. Calculations of librational frequencies at the q = 0 point prove the misinterpretation of observed bands in Raman spectrum. It was shown that the ratio p = H/D for the given librational frequencies cannot be treated as a correct criterion for assignment of the observed bands. Agreement between calculated elastic constants of a biphenyl crystal with experimental values is fairly good. T and L tensors of thermal vibrations could not be compared with experimental values because we lacked experimental data. Within the temperature range from 80 to 340[ddot]K, the specific heat C v for a biphenyl crystal is the following function of temperature: