A theoretical evaluation of the root-mean-square amplitudes of vibration in XeF2and XeF4

The general formulation necessary for the calculation of the root-mean-square amplitudes of vibration of square planar molecules is presented within the framework of Morino's method. The root-mean-square amplitudes of vibration of the Xe-F, the adjacent F…F, and the trans F…F interatomic distances in XeF4 have been theoretically estimated to be 0·0465 å, 0·1101 å, and 0·0633 å, respectively at 298°K. While the experimental value of the last of these has not yet been ascertained, the first two compare favourably with the reported values of 0·05 å and 0·10 å. Furthermore, the root-mean-square amplitudes of vibration of the Xe-F and F…F interatomic distances in XeF2 were calculated to be 0·0469 å and 0·0638 å respectively at 298°K. The striking resemblance of these values with those of XeF4 suggests strongly that the bonding in both molecules must be similar.