1 research outputs found
Molecular Dynamics with Conformationally Dependent, Distributed Charges
Accounting for geometry-induced changes in the electronic
distribution
in molecular simulation is important for capturing effects such as
charge flow, charge anisotropy, and polarization. Multipolar force
fields have demonstrated their ability to correctly represent chemically
significant features such as anisotropy and sigma holes. It has also
been shown that off-center point charges offer a compact alternative
with similar accuracy. Here, it is demonstrated that allowing relocation
of charges within a minimally distributed charge model (MDCM) with
respect to their reference atoms is a viable route to capture changes
in the molecular charge distribution depending on geometry, i.e.,
intramolecular polarization. The approach, referred to as “flexible
MDCM” (fMDCM), is validated on a number of small molecules
and provides accuracies in the electrostatic potential (ESP) of 0.5
kcal/mol on average compared with reference data from electronic structure
calculations, whereas MDCM and point charges have root mean squared
errors of a factor of 2 to 5 higher. In addition, MD simulations in
the NVE ensemble using fMDCM for a box of flexible
water molecules with periodic boundary conditions show a width of
0.1 kcal/mol for the fluctuation around the mean at 300 K on the 10
ns time scale. For water, the equilibrium valence angle in the gas
phase is found to increase by 2° for simulations in the condensed
phase which is consistent with experiment. The accuracy in capturing
the geometry dependence of the ESP together with the long-time stability
in energy conserving simulations makes fMDCM a promising tool to introduce
advanced electrostatics into atomistic simulations