关键词: 静电能, 交换能, 分子间作用, 硝酰胺

The electrostatic and exchange energies between two interacting nitramide molecules at several intermolecular separations (R) were derived based upon symmetry-adapted perturbation theory (SAPT) and using perturbative and nonperturbative methods. The obtained electrostatic energies with orbital relaxation not only include the fourth order contributions with single, double, quadruple and triple excitations, but also contain fifth and higher order contributions from CCSD theory. It was found that the fourth order triple excitation term is more important than the sum of these fifth and higher order contributions. The derived exchange energies with intramonomer correlation effects arrive at CCSD level. The single exchange approximation used for computing correlation corrections to exchange energy was found to be reasonable only in the region near the Van der Waals minimum distance of 0.42 nm for nitramide dimer. The R-dependency of the electrostatics has two different stages with R from 0.32 to 1.42 nm, (R^－7.64 for R less than 0.47 nm, inclusively; and (R^－3.97 for R over 0.47 nm. The exchange energy takes on a clear characteristic of short-range interaction, R-dependency of which is in the formula of 21.061exp(－R/ 0.318). The influence of intramonomer electron correlation on and was also found to be remarkable in the dimer system.

Key words: electrostatic energy, exchange energy, intermolecular interaction, nitramide