COMPUTATIONAL CHEMISTRY OF THE SILICON-NITRIDE SURFACE .1. WATER, AMMONIA, AND WATER-AMMONIA COMPLEX

This paper deals with computational modeling of structure and properti es of the silicon nitride surface zone using combined computational an d real experiments. The computational experiment implies quantum chemi cal calculations of structure and vibrational spectra of polyatomic cl usters. The real experiment suggests measurement and analysis of vibra tional spectra. For quantum chemical calculations, semiempirical metho ds (MNDO and AM1) were chosen. In most calculations, the MNDO/H method was preferred because of the presence of many H-bonds in the surface zone. For verification of calculations, we calculated the structures a nd vibrational spectra of water and ammonia molecules and the water-am monia complex and compared the results with experimental and ab initio (extended basis) data; MNDO/H proved to be an optimal method giving r eliable results.