This work presents our investigations of mezomorphic properties of two polymorphic liquid crystals, namely, 4-nonyloxy-4-butoxyphenyl benzoate and N-(-4-heptyloxybenzylidene-4-butylaniline) in a wide temperature range, particularly, in the phase transition regions. By means of an original experimental method, the heterophase regions and also the phase transition temperatures have been determined for these materials with high accuracy. These phase transition intervals have been analyzed using a mean field model.
ur t se ve n D epart ment of Phy si cs, I stan b ul T echnical U ni versity , Masla k, Istanbul, T urkey ( Recei ved October 9, 2000) W e calcula te d in this study the Raman fre quencies of some lattice mo des in the meltin g region of ammonia solid I. T he Raman frequencies of those phonon mo des were obtained through the Gr uneisen relation using the volume data for the ammonia solid I from the literature. Our calculated Raman frequencies require for comparison the exp erimental Raman frequencies measured as a function of pressure for some Ùxed temp eratures in the ammonia solid I. (5 57)
We have performed in this study the calculation of the Raman frequencies for two translational modes and
one librational mode in the ammonia solid I near the melting point. We have obtained the Raman frequencies
as a function of temperature for some fixed pressure by means of the Grüneisen relation using the volume
data from the literature. Our calculated Raman frequencies can be compared with experimental data available
in the literature.
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