A potential function for describing intermolecular interactions in the hydroxylamine dimer

A potential function that describes the interaction between two hydroxylami ne molecules has been developed from ab initio determined molecular propert ies and IMPT calculations for various dimer configurations using the 6-311G ** basis set. The function comprises an electrostatic term in the form of a series of multipoles distributed over the atoms and an exponential repulsi ve term determined by fitting the results for the dimer. The dispersive ter m is expressed according to a London formula as a function of distributed s pherical polarizabilities, and the contribution of induction is a function of the polarizabilities, distributed over the atoms. The proposed function reproduces the properties of the different minima for the hydroxylamine dim er with an accuracy similar to that of MP2 calculations. The electrostatic contribution predominates in all the configurations obtained, and the maxim um possible number of X-H ... N hydrogen bonds is always favored. In additi on, the function was employed to determine the lowest-energy configurations for the trimer, and the results were compared to those from ab initio calc ulations employing several methods.