| Автор | N W Grimes |
| Автор | Robin W Grimes |
| Дата выпуска | 1998-06-22 |
| dc.description | For the theoretical calculation of low-frequency in crystal ion polarizabilities two independent approaches have been developed and shown to give rather similar results for the rock-salt structured oxides of the alkaline earths. The theory based on the lattice dynamical shell model for alkali halides is believed to have successfully provided values for individual ion polarizabilities in those crystals. The alternative theory which relies on known ionic radii, however, through a new prediction, reveals that the former provides a poor fit for fluorides with gradual improvement for chlorides, bromides and iodides in that order. It seems that the shell model is inadequate for describing the dielectric behaviour of the alkali halides. The observed discrepancies are attributed to the neglect of second-nearest neighbour interactions which have been shown to be important for the theory of their cohesion. New values for the in crystal polarizabilities of individual alkali and halide ions are derived for ions in environments with sixfold and with eightfold co-ordination. These satisfy the quantum mechanical expectation that such polarizabilities depend on the square of the corresponding ionic radius and on the number of electrons known to occupy the outermost subshell. The new analysis of the dielectric data of alkali halides is now consistent with the treatment of the corresponding data from oxides. |
| Формат | application.pdf |
| Издатель | Institute of Physics Publishing |
| Название | The shell model for alkali halide crystals: do the equations adequately describe their dielectric behaviour? |
| Тип | paper |
| DOI | 10.1088/0953-8984/10/24/019 |
| Electronic ISSN | 1361-648X |
| Print ISSN | 0953-8984 |
| Журнал | Journal of Physics: Condensed Matter |
| Том | 10 |
| Первая страница | 5433 |
| Последняя страница | 5437 |
| Выпуск | 24 |
