Factor Group Splitting and Multipole Interactions in Molecular Crystals
An electrostatic interaction potential has been used to explain the factor group splitting in several molecular crystals composed of small inorganic molecules. The potential function is expanded in terms of molecular multipole moments. It is shown that the dipolar coupling mechanism is not sufficient to reproduce the observed splitting in these crystals and that the quadrupolar interactions play a dominant role. In case of hydrogen halide and alkaline earth hydroxide crystals dipole-dipole, dipolequadrupole and quadrupole-quadrupole interactions can explain the splitting. The values of the quadrupole moment derivatives obtained from such studies are compared with those obtained from ab initio calculations. The possibility of obtaining quadrupole moment derivative from the observed factor group splitting will be discussed. The role of quadrupolar interaction in the case of cyanogen bromide crystal will also be examined.
KeywordsQuadrupolar Interaction Molecular Crystal Multipole Moment Hydrogen Halide Group Splitting
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