Accession Number : ADA324581

Title :   First-Principles Calculations for Ferroelectrics.

Descriptive Note : Final rept. 1 Nov 93-31 Dec 96,

Corporate Author : COLLEGE OF WILLIAM AND MARY WILLIAMSBURG VA DEPT OF PHYSICS

Personal Author(s) : Krakauer, Henry

PDF Url : ADA324581

Report Date : 01 MAY 1997

Pagination or Media Count : 8

Abstract : First-principles calculations for ferroelectrics reveal the existence of extended instabilities as a function of wavevector in KNbO3 and SrTiO3. The scope of the first-principles results is extended through the use of effective Hamiltonians, determined with no empirical or experimental input, using a database of first-principles calculations. Molecular dynamics simulations using these effective Hamiltonians then predict ferroelectric phase transition temperatures, phonon softening, and diffuse X-ray scattering behavior. These calculations also demonstrate for the first time the existence of preformed dynamic precursor chain-like structures in KNbO3 and BaTiO3, well above the ferroelectric transition temperatures.

Descriptors :   *FERROELECTRIC MATERIALS, INPUT, SIMULATION, COMPUTATIONS, DYNAMICS, PHASE TRANSFORMATIONS, TRANSITION TEMPERATURE, OXIDES, NIOBIUM, X RAY SCATTERING, TITANIUM, PHONONS, BARIUM, STRONTIUM, TITANATES, MOLECULAR PROPERTIES, INSTABILITY, POTASSIUM, HAMILTONIAN FUNCTIONS, NIOBATES, DIFFUSE REFLECTION, FERROELECTRICITY.

Subject Categories : Inorganic Chemistry
      Ceramics, Refractories and Glass
      Electricity and Magnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE