Hydrogen bonds: a comparison of semiempirical and ab initio treatments

H-bonding interactions calculated using the AM1, PM3 and SAM1 semiempirical molecular orbital methods are compared with the best available ab initio calculations for several intermolecular interactions of interest. acetic acid dimers, water/acetylene, water/HCN, farmaldehyde/acetylene, formaldehyde/HCN, ozone/acetylene, ozone/HCN, acetylacetone, melamine/cyanuric acid, and nitromethane/ammonia. Experimental Values are also presented where available. The energetic comparisons are based upon enthalpies of interaction from the ab initio calculations after counterpoise and vibrational corrections have been applied. Overall, AM1 seems to do best, except for O-H ... O interactions, where none of the three methods excel. (C) 1997 Elsevier Science B.V.