General Charge Transfer Dipole Model for AMOEBA-Like Force Fields

The development of highly accurate
force fields is always
an importance
aspect in molecular modeling. In this work, we introduce a general
damping-based charge transfer dipole (D-CTD) model to describe the
charge transfer energy and the corresponding charge flow for H, C,
N, O, P, S, F, Cl, and Br elements in common bio-organic systems.
Then, two effective schemes to evaluate the charge flow from the corresponding
induced dipole moment between the interacting molecules were also
proposed and discussed. The potential applicability of the D-CTD model
in ion-containing systems was also demonstrated in a series of ion–water
complexes including Li+, Na+, K+,
Mg2+, Ca2+, Fe2+, Zn2+, Pt2+, F–, Cl–, Br–, and I– ions. In general, the D-CTD
model demonstrated good accuracy and good transferability in both
charge transfer energy and the corresponding charge flow for a wide
range of model systems. By distinguishing the intermolecular charge
redistribution (charge transfer) under the influence of an external
electric field from the accompanying intramolecular charge redistribution
(polarization), the D-CTD model is theoretically consistent with current
induced dipole-based polarizable dipole models and hence can be easily
implemented and parameterized. Along with our previous work in charge
penetration-corrected electrostatics, a bottom-up approach constructed
water model was also proposed and demonstrated. The structure-maker
and structure-breaker roles of cations and anions were also correctly
reproduced using Na+, K+, Cl–, and I– ions in the new water model, respectively.
This work demonstrates a cost-effective approach to describe the charge
transfer phenomena. The water and ion models also show the feasibility
of a modulated development approach for future force fields.