Understanding structural effects of multipole moments on aqueous solvation of ions using the soft-sticky dipole–quadrupole–octupole water model

The effects of water multipole moments on the aqueous solvation of ions were determined in Monte Carlo simulations using soft-sticky dipole–quadrupole–octupole (SSDQO) water. Water molecules formed linear hydrogen bonds to Cl− using the new SSDQO1 parameters, similar to multi-site models. However, the dipole vector was tilted rather than parallel to the oxygen–Na+ internuclear vector as in most multi-site model, while experiment and ab initio molecular dynamics simulations generally indicate a range of values between tilted and parallel. By varying the multipoles in SSDQO, the octupole was found to determine the orientation around Na+. Moreover, analysis of the multipoles of more conventional models is predictive of their performance as solvents.