Investigation of the β-γ phase transition in single crystal malononitrile by polarized Raman spectroscopy

Authors

S.J. Bonafede, University of Nebraska - Lincoln
Craig J. Eckhardt, University of Nebraska - LincolnFollow

Date of this Version

October 1993

Comments

Published by American Institute of Physics. J. Chem. Physics Vol. 99, No. 8, 15 October 1993. ©1993 American Institute of Physics. Permission to use. http://jcp.aip.org/.

Abstract

Temperature dependent, polarized Raman spectra in the lattice mode region for sublimed, single crystal malononitrile through the β-γ phase transition (T_c=294.7 K) are reported. Symmetry assignments and frequencies of vibrational modes are made and compared to previous studies. Nine out of 12 possible lattice modes are observed in each phase with three of the observed modes being affected by the phase transition. The temperature dependence of these three affected modes is attributed to cyano group and molecular dipole interactions between molecules in the crystal. The behavior of malononitrile through the β-γ phase transition is analogous to the smectic A↔nematic phase transition reported for cyano-based, liquid crystal systems.