Na+ in liquid hydroxylamine: pair potential function from ab initio calculations and Monte Carlo computer simulation of a 0.36 M NaCl solution (2 NaCl/200 NH2OH) Original Research Article

Ab initio calculations at the Hartree-Fock Self Consistent Field (HF-SCF) level have been carried out to determine the interaction hypersurface for a sodium cation in the field of a hydroxylamine molecule. The quality of the selected wave function and basis set used in sampling the interaction energy surface of the complex has been tested and compared with alternatives. The Na+NH2OH surface is characterized by two main minima of −24.1 and −19.3 kcal mol−1, in which the sodium cation is coordinated to oxygen and nitrogen of hydroxylamine, respectively. An analytical pair potential expression consisting of a Coulomb and several R−n terms was constructed to fit the 1352 calculated single energy points of the obtained energy surface. Subsequent Monte Carlo statistical thermodynamic simulations for a dilute solution of sodium chloride in hydroxylamine are also reported. The structure of the local solution environment around the cation is analyzed by means of radial and angular distribution functions, density maps, coordination number and energy distributions.