Journal of Physical Chemistry A, Vol.106, No.41, 9529-9532, 2002
Many-body effects in combined quantum mechanical/molecular mechanical simulations of the hydrated manganous ion
Two different quantum mechanics/molecular mechanics molecular dynamics simulation techniques QM/ MM-MD) are compared using as an example the hydrated manganous ion. One includes a perturbation field composed of point charges representing the bulk solvent molecules polarizing the QM region in addition to a quantum chemically derived two-body potential-The other includes the two-body potential plus a threes body correction function. In both simulations, the QM region comprises the ion and its first hydration shell and hence includes all many-body terms up to the QM frontier. The structure of the hydrated ion is discussed in terms of radial distribution functions, coordination numbers, and angular distributions. The results show that both QM/MM-MD techniques agree well with experimental findings for the first-shell hydration structure. QM/MM-MD including point charges has been found to be a satisfactory and economic alternative in studying the first hydration shell without the need to undergo the time-consuming procedure of constructing a three-body correction function from thousands of single-point ab initio computations.