Combined quantum mechanical/molecular mechanical (QM/MM) simulations are a common computational technique used to investigate enzymatic reactions and pKa shifts in solution. Subtle changes in the non-electrostatic, non-bonded forces around the QM region drastically affect the accuracy of energy barriers and pKa values of these simulations. Frequently these interactions are treated with a fixed Lennard-Jones potential. However, a static model does not allow for physically meaningful changes, such as atoms undergoing drastic changes in partial charge or chemical environment, to be represented in the physics of the simulation. This work introduces QXD, a charge-dependent exchange and dispersion model is introduced which couples the non-electrostatic non-bonded QM/MM interactions with the underlying electronic structure in a self-consistent manner. Comparisons with quantum chemical calculations and preliminary data of reactions in solution indicate QXD is more accurate and robust model than the conventional Lennard-Jones models, representing a significant advance in QM/MM simulations.

Self-consistant, charge-dependent interaction potentials for solution phase QM/MM simulations

245th National Meeting (2013)

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