Hybrid force field

MMVB is a hybrid force field, which uses MM to treat the unreactive molecular framework, combined with a valence bond (VB) approach to treat the reactive part. The MM part uses the MM2 force field [58], which is well adapted for organic molecules. The VB part uses a parametrized Heisenberg spin Hamiltonian, which can be illustrated by considering a two orbital, two electron description of a sigma bond described by the VB determinants... 

Hybrid Force Field-Electronic Structure Methods... 

In many force fields, truncation schemes are often used to reduce the number of non-bonded electrostatic and Lennard-Jones interactions that need to be calculated. Such schemes, are readily incorporated into the.inter-action Hamiltonian either by omitting all interactions that have a distance greater than some cutoff or by multiplying the appropriate interactions by a tapering function that reduces the interactions to zero beyond a certain distance. It is to be noted that in some hybrid force fields (see, for example, [35]) the electrostatic interaction terms are not included and the QM/MM interaction is due solely to the Lennard-Jones terms (and link-atoms if they are present). This could be a reasonable approximation in non-polar systems (such as the transition metal complexes for which some of these force fields were developed) but it will not be sufficiently accurate in the general case. 

In this contribution, we present the theory behind the GEM method and recent advances and results on the application of two hybrid GEM potentials. In Section 8.2, we provide a brief review of the analytical and numerical density fitting methods and its implementation, including the methods employed to control numerical instabilities. This is followed by a review of the procedure to obtain distributed site multipoles from the fitted Hermite coefficients in Section 8.3. Section 8.4 describes the extension of reciprocal space methods for continuous densities. Section 8.5 describes the complete form for GEM and a novel hybrid force field, GEM, which combines term from GEM and AMOEBA for MD simulations. Finally, Section 8.6 describes the implementation and initial applications of a multi-scale program that combines GEM and SIBFA. 

To enable the performance of MD simulations, a hybrid force field called GEM was developed. GEM combines the Coulomb and exchange-repulsion terms from GEM with the polarization, van der Waals (modified) and bonded terms from AMOEBA. The functional form for GEM is thus... 

HYBRID FORCE FIELD ELECTRONIC STRUCTURE METHODS... 

Kamiya, N., Watanabe, Y. S., Ono, S., and Higo, J. 2005. AMBER-based hybrid force field for conformational sampling of polypeptides. Chem. Phys. Lett. 401 312. 

---