A. Basu’s research while affiliated with Jadavpur University and other places

The importance of the three‐body interaction in the study of simple ionic solids with centrosymmetric structure is both, theoretically and empirically well established. But so far there is no attempt to investigate its significance in the properties of ionic crystals belonging to fluorite and antifluorite structures. In contrast to said alkali halides the absence of the centre of symmetry for this structure implies complications which make a direct estimate of this effect quite difficult. From an analysis of the elastic data the inadequacy of a two‐body central interaction to describe the elastic constants of such crystals is demonstrated. An order of estimate is made of the three‐body interaction in the elastic properties of the calcium fluorite crystal from the HF wavefunctions of the ions. For the other crystals where the Clementi wavefunctions for the ions are not available the estimate is done directly from the elastic constants. The order of magnitude of this interaction obtained for the different crystals is comparable and lies in the range observed for other ionic solids. Further this investigation apart from indicating the importance of the three‐body interaction also accounts for the anomalies in the previous calculations. Finally some of the limitations of the present calculation are pointed out.