On the role of d orbitals in H3PO

The role of d orbitals in the bonding of H3PO is studied using our develope d method of polarized fregment orbital analysis. The whole molecule H3PO is divided into two fragments H3P and O. Then the polarized fragment orbitals in molecular environment(FOM) are calculated using 6-31G* basis set. Whole molecule is recalculated using the FOM basis set in which the d functions are deleted. The optimized P-O bond length is close to the result of RHF/6- 31G*. The results of this study lead to a refined picture of the nature of hypervalence in H3PO. The role of d functions of phosphorus atom in the wav e function of H3PO is only a polarized function just as p functions are cus tomarily added to hydrogen atom s functions. The "valence d orbital" role s hould be rejected in molecule H3PO.