MEANS SQUARE DISPLACEMENTS OF A SUBSTITUTIONAL DEFECT AND ITS NEAREST NEIGHBOURS IN KI

The means square displacements of both the cation and anion substitutional defects and those of their nearest neighbours in KI are calculated in the frame work of a scattering matrix formalism. Our results show that the means square amplitudes of the defect atom such as the Rb+ in KI is much larger than the value of Rb+ in RbI as also of K+ in KI. The means square displacements of the nearest neighbours in the defect environment are not that significanltly altered from their values in the host crystal environment. The other salient features observed from our calculations are also discussed

THE LOCALIZED MODES DUE TO PHOSPHEROUS DEFECTS IN CADMIUM TELLURIDE

Dutt and Spitzer have experimentally observed the localized vibrational modes related to the phospherous defect in CdTe and reported that this defect may go either to substitutional or interstitial site. In this paper we study theoretically this phospherous defect behaviour for these two possible sites by Green's function technique and we believe that phospherous goes interstitially rather than substitutionally. The localized modes paired with Ga, In and Al are also investigated and discussed in the light of the experimental results

A GREEN'S FUNCTION STUDY OF THE U CENTRE IN BaClF AND SrClF

A Green's function investigation of the localized and resonant modes due to U centres in the tetragonal BaClF and SrClF crystals is made for the first time.The lattice Green's functions are computed using the normal modes and eigenvectors obtained on a shell model which explained the long wavelength phonons satisfactorily. The U centre has D2d point symmetry and the relevant matrices are blockdiagonalised group theoretically. The U centre modes come under E and B2 representations.The force constant weakening to fit the experimental E mode is 24 % whereas for the B2 mode the weakening is only 12 %. These are compared with earlier work on molecular model and on the U centres in fluorites. The possible phonon resonances are also examined and he possibility of their experimental detection is discussed

CALCULATION OF DEFECT ENTROPIES IN IONIC CRYSTALS IN THE QUASIHARMONIC APPROXIMATION : APPLICATION TO FLUORITES

No abstract availabl

Lattice dynamical appraisal of the anisotropic Debye-Waller factors in graphite lattice

SIGLEITItal

Dynamics of simple defect clusters in alkaline earth fluorides

SIGLEITItal