Optical and dielectric properties and lattice dynamics of some fluorite structure ionic crystals

Abstract

Some optical, dielectric and lattice properties of three alkaline earth fluorides (calcium, strontium and barium fluorides) and of two other isomorphous fluorides (cadmium and lead fluoride) are reported. Results obtained from experimental studies on infrared and Raman spectra give the fundamental transverse and longitudinal optical lattice mode frequencies, the two-phonon absorption spectra, and the spectra associated with U centre absorptions. Calculations of phonon dispersion curves, density of states and density of com­bined states functions, have been made for all five crystals and these are compared with the experimental results.

On a universal relation for defect data in solids

“…In the usual case of a linear ln versus 1 T plot, the energy E is the enthalpy m h for the corresponding migration (re-orientation) process. Here, we shall focus on the so called R 1 -relaxation that is associated with complexes (electric dipoles) in which the (These are comparable with the values measured in Refs [43] and [44]). Taking their mean value 396 cm -1 , Eq (7) leads to the experimental m s values inserted in Table 1.…”

Theory of noncontact friction for atom-surface interactions

“…Indeed, a collection of references on optical properties of solids has been given in Refs. [23,[25][26][27][28][29]. Following Ref.…”

“…The integral (17a) carries an explicit temperature dependence in view of the Boltzmann factor, which appears in disguised form (hyperbolic sine function in the denominator), but there is also an implicit temperature dependence of the dielectric response function [ǫ(ω) − 1]/[ǫ(ω) + 1], which has been analyzed (for CaF 2 ) in Refs. [27][28][29].…”

Local structure of Gd3+ impurity center at cubic sites in fluorites

“…The parameters of the F--F-interaction potential have been obtained non-empirically using the Hartree-Fock method and the configuration interaction method [15]. The parameters of the Me2+-F -short-range repulsive potential have been obtained by fitting the calculated crystal properties to the experimental data for the crystals MeF2: the lattice constant (see Table 4), the dielectric constants e0 and soo, the elastic constants Cl~, C~~, and C44, the frequencies of the fundamental vibrations COro and o~ [16][17][18][19][20]. The parameters of the short-range electrostatic screening have been calculated by numeric integration of the interaction of the free ions electron densities.…”