On the Phase Transition of N-Isopropylcarbazole.
Abstract
The elastic properties of N-isopropylcarbazole (NIPC), a pyroelectric molecular crystal, are investigated by Brillouin scattering. The full elastic constant tensor is determined at 295 K and the temperature dependence of the elastic constants are given. The major experimental finding reported is the anomaly of the LA a-axis mode governed by the c sub 11 elastic constant. This mode exhibits a pronounced downward bending on both sides of the nonferroic, first order phase transition at ca. 137 K. Symmetry allowed linear-quadratic and biquadratic couplings between the Brillouin zone boundary one-dimensional order parameter and the zone center strain introduced into the Landau free-energy do not account for the observed anomaly. The transition is characterized in terms of a strong dispersion of the c sub 11 elastic constant and a large dynamical critical behavior. By combining the c sub 11 elastic constant data and the Brillouin scattering LA a-axis mode halfwidth data through a Landau-Khalatnikov process, a relaxation time is extracted satisfying mean-field dependence characteristic of critical slowing down of the order parameter.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1986
- Accession Number
- ADA172349
Entities
People
- Elliot R. Bernstein
- Robert D. Nowak
Organizations
- Colorado State University