| Numéro |
J. Phys. Colloques
Volume 42, Numéro C6, Décembre 1981
International Conference on Phonon Physics
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|---|---|---|
| Page(s) | C6-905 - C6-907 | |
| DOI | https://doi.org/10.1051/jphyscol:19816269 | |
J. Phys. Colloques 42 (1981) C6-905-C6-907
DOI: 10.1051/jphyscol:19816269
A GREEN'S FUNCTION STUDY OF THE U CENTRE IN BaClF AND SrClF
K.R. Balasubramanian et T.M. HaridasanSchool of Physics, Madurai Kamaraj University, Madurai 625021, India
Abstract
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.