A Study on the Pairing Theorem of AB_n and Its Application
Yao Chongfu ( Department of Chemistry )
On the basis of LCAOMO method, the structure of ABn(n = 2-7) of nontransition elements has been discussed in this paper. By means of the Block Matrice Method; the formulae(αb - E)q-p | (αb - E) A.-B B| =O(q p)and (αa-E)p -q| (αa -E)D-B B| -O(p q) have becn derived from the secular determinant. It is similar to the Pairing Theorem of alternant hydrocarbons. I ased on it, the total number of nonbonding, bonding and antibonding orbits is obtained. They are|q-p|, p (or q) and p (or q) respectively. Their energy levels about a are symmetrically disposed. The number of bonding, nonbonding and antibonding orbits of ABn (n = 2-7) systems, the occupied situation of valence electrons and bond orders can be determined easily. The average bond lengths may further be predicted. The results agree well with the experimental data. It is showed that the similar types of ABn with equal valence electrons are the same not only in the geometric arrangement, but also in the bond order.