Basis Set Superimposition Error

Following the introdnction of a directional hydrogen bonding potential function into MM3, the parameterization of the force field for the ammonia dimer was undertaken anew . Three conformers were considered, namely 28, 29 and a bifurcated structure 31, and were calcnlated ab initio at the 6-31G level. The results (after corrections for Basis Set Superimposition Error BSSE) favor the linear dimer over the cyclic one by 0.4 kcalmol and yield dimerization energies of —2.49, —2.09 and —0.62 kcalmol for 28, 29 and 31, respectively. A comparison of force field (original MM3 and MM3 with the directional hydrogen bonding function) and ab initio resnlts for the three ammonia... 

---