SANDUSKY, KW and PAGE, JB and ROSENBERG, A and SIEVERS, AJ (1993) POCKET VIBRATIONAL-MODES IN CRYSTALS - THEORY AND EXPERIMENT. PHYSICAL REVIEW B, 47 (10). pp. 5731-5747. ISSN 0163-1829,
Full text not available from this repository.Abstract
A perturbed-shell-model calculation for the T=0 K on-center dynamics of the thermally unstable impurity system KI:Ag+ predicts three nearly degenerate localized gap modes of different symmetry with highly unusual displacement patterns: the displacements are peaked on the defect's fourth-nearest neighbors, with negligible displacements on the defect or its nearest neighbors. The model predictions are in good agreement with far-infrared isotope-effect measurements, providing a direct confirmation of the existence of these ''pocket'' modes. We also discuss an experimental technique that yields a major reduction in the uncertainties in the measured temperature dependence of the absorption strength due to the infrared-active pocket mode. As a result, we show that the previously observed disappearance of this mode's absorption between 1.2 and 25 K occurs with exactly the same temperature dependence as that of a low-frequency resonant mode whose displacements are instead localized at the impurity and its nearest neighbors. This result, together with the calculated displacement patterns of the pocket and resonant modes, indicates that the anomalous thermally driven (on-->off)-center transition of the Ag+ impurity in KI involves the entire coupled defect-host system around the impurity.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | 2 ELASTIC CONFIGURATIONS; DEFECT; |
| Depositing User: | Dr. Gernot Deinzer |
| Last Modified: | 19 Oct 2022 08:42 |
| URI: | https://pred.uni-regensburg.de/id/eprint/54103 |
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