Theoretical study of hydrogenhyphen;bonded trimers. Threehyphen;body nonadditive interactions between ammonia molecules

摘要

The ineraction energy of the system (NH3)3was calculated for different geometrical arrangements and mutual orientations between the ammonia monomers. The calculations used the SCF LCAO MO method with a nearhyphen;minimal set of Gaussian functions. The analysis of the threehyphen;body terms shows that although nonadditive contributions are comparatively small, they do play a role in the relative stability of the different structures for the trimer. The longhyphen;range induction nonadditive terms are evaluated, turning out to be substantially less dominant than for water trimers. The present results are related to existing experimental data on ammonia polymers and solid ammonia crystals.