Abstract
The atom-atom interaction model has been extended to the case of and it is shown that the observed vibrational frequencies can be satisfactorily reproduced by only three force constants. However, the calculation leads to a frequency reversal in the Davydov pair which is very similar to that found earlier for and . Since Mo is somewhat less ionic than the two gallium compounds, we suggest that the frequency reversal may not be due to the long-range interactions proposed earlier. We discuss the possible role of short-range multipolar interactions.
- Received 4 November 1982
DOI:https://doi.org/10.1103/PhysRevB.28.2237
©1983 American Physical Society