Study of relationship of atomic orbital hybridization with bonding using hybridization displacement charge: optimal hybridization principle

Hybridization displacement charges (HDC) were computed for several symmetric molecules employing the ab initio HF/6-31G** method. HDC calculations provide several point charges near as well as far from the atoms in molecules. The HDC method preserves the contribution of each atom to the component of molecular dipole moment arising due to atomic orbital hybridization. Variation of total HDC with bond length showed a maximum or a shoulder near the optimized bond length in each case. The linear correlation coefficient between the optimized bond lengths and the positions of maxima or shoulders was found to be 0.81. According to the t-test, this correlation coefficient is significant at a level less than 0.5% showing that the correlation is meaningful. Thus it is concluded that bonding in molecules follows a principle that can be termed as Optimal Hybridization Principle (OHP). This principle, like the Maximum Overlap Principle (MOP), can be used to explain bonding in molecules in a qualitative manner. The HDC components arising due to mixing of different s and p types of orbitals usually vary with bond length quite differently. Thus bonding is usually controlled by hybridization of some specific atomic orbitals in molecules which generally include those belonging to the next higher shell than the valence shell of the atom under consideration.