Parameter-free Fenske-Hall SCF MO method was used to calculate the electronic structures of three kinds of D-A complexes of ammonia: H3N-AX (A = H, Li; X = F, Cl); H3N-BX3 (X = H and halogen) and H3N-XX' (X, X' = F, Cl). Based on the wave functions thus obtained, natural hybrid orbital anal. was carried out. Mol. valency was introduced and computed, which show that the valency increments of ammonia vary monotonically with the interaction intensities between acceptor (A) and donor (D) in a series of adducts. Moreover, our calculation also demonstrates that the nature of D-A interaction can be interpreted in terms of the unsatn. of mol. valency.

Key words: AMMONIA, ELECTRONIC STRUCTURE, HYDROGEN BONDS, ADDITION COMPOUNDS, LITHIUM BOND