Improper Ferroelectricity: A Theoretical and Experimental Study.
Final rept. no. 2, 1 Jun 83-31 May 87,
NEBRASKA UNIV LINCOLN
Pagination or Media Count:
The theoretical and experimental investigations proposed for this period have been completed. First-principle theoretical lattice-dynamics calculations on the high and low-temperature commensurate phases of Rb2ZnC14, K2ZnC14, and BaMnF4 have indicated the origin of the incommensurate behavior in the intermediate phase. Molecular dynamics M-D calculations were developed that demonstrate how the orientational disorder develops in the molecular anion sublattice and how it relates to the incommensurate and commensurate phase transitions. These M-D calculations have also demonstrated the importance of including ionic polarization in these calculations. A general theory, based on latent symmetry, of incommensurate behavior in these, and probably many similar materials, has been developed and submitted for publication. Raman spectra have been obtained for various phases of these materials. An analytical method was developed for deconvoluting these severly overlapped spectra so that a one-to-one comparison with the theoretically-predicted lines could be made.
- Electricity and Magnetism