Accession Number : AD0825499

Title :   MICROSCOPIC THEORY OF FERROELECTRICITY.

Descriptive Note : Final scientific rept. Jan 64-31 Dec 66,

Corporate Author : ISRAEL ATOMIC ENERGY COMMISSION YAVNE SOREQ NUCLEAR RESEARCH CENTRE

Personal Author(s) : Englman, Robert ; Ruppin, Raphael ; Yatom, Haim

Report Date : NOV 1967

Pagination or Media Count : 100

Abstract : A detailed formulation is given to the supposition that a polarized phase in ionic dielectrics can arise from the vibronic instability mechanism (Jahn-Teller effect) due to the valence electrons. The thermodynamical consequences of this hypothesis are worked out for BaTiO3. The contribution of the vibronic coupling to the temperature dependence of the soft mode in BaTiO3 is calculated. We use a frequency renormalization method to derive the effect of the soft mode on other long wavelength modes near the transitions. Last, the behavior of the optical vibrational frequencies in a finite-sized (or domain-structured) specimen is studied. (Author)

Descriptors :   (*FERROELECTRICITY, BAND THEORY OF SOLIDS), BARIUM COMPOUNDS, TITANATES, PHONONS, PIEZOELECTRIC EFFECT, CRYSTAL STRUCTURE, DIELECTRIC PROPERTIES, INTERACTIONS, FREE ENERGY, ELECTRIC FIELDS, PHASE STUDIES, INFRARED SPECTRA.

Subject Categories : Crystallography
      Electricity and Magnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE