Relationship for dipole moment functions of alkali halides

An effective relationship between the dipole moment functions(DMFs) and the polarisabilities of the atomic ions, the ionisation potential and the electron affinity of the corresponding atoms is reported for alkali halides in their ground electronic states. To test the quality of predicted DMFs, ab initio calculations were performed systematically. For almost all of the twenty alkali halide molecules AX(A = Li, Na, K, Rb, Cs; X = F, Cl, Br, I) the predictions with the present relationship are in good agreement with high-quality ab initio DMFs in a large or relatively larger range around equilibrium. The obtained relationship is expected of significance to highly-ionic species with heavy atoms.