The explicit polarization (X-Pol) method is a fragment-based quantum mechanical model suitable for macromolecular systems.  In general, the X-Pol method can be formulated with a combination of any electronic structural methods, representing different individual monomer fragments. Furthermore, the X-Pol theory provides a novel theoretical framework for the development of next generation force fields that include electronic polarization and charge transfer explicitly. Here we illustrate the implementation of the X-Pol method into the Gaussian-09 program, in both nonvariational and variational schemes. Both schemes enable the incorporation of any arbitrary combination of electronic structural methods to treat different fragments, as is illustrated by the analysis of an acetic acid-water complex and a protonated water cluster H+(H2O)6. In the variational version, the wavefunction for the entire system is optimized to yield the minimum total electronic energy. This further provides analytic gradients and thus is suitable for molecular dynamic simulations.

General implementation of the X-Pol method

243rd National Meeting (2012)

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