Many-body polarizable force field

Borodin, 0., and Smith, G. D. Development of many-body polarizable force fields for Li-battery components 1. ether, alkane, and carbonate-based solvents. /. Phys. Chem. B, 110, 6279-6292 [2006],... 

Borodin, O. Smith, G. D., Development of Many-Body Polarizable Force Fields for Li-Battery Applications 2. Litfsi-Doped Ohgoether, Polyether, and Carbonate-Based Electrolytes. J. Phys. Chem. B 2006,110, 6293-6299. 

Polarizable force fields for nonbiological systems also exist. A many-body polarizable force field by Smith and coworkers was developed and applied to the simulations of ion conduction in polyethylene oxide Cummings and coworkers developed an interesting Gaussian charge polarizable force field for ions and in A polarizable force field for ionic... 

Specific polarization effects, beyond those modelled by a continuum dielectric model and the movement of certain atoms, are neglected in MIF calculations. Many-body effects are also neglected by use of a pair-wise additive energy function. Polarizable force fields are, however, becoming more common in the molecular mechanics force fields used for molecular dynamics simulations, and MIFs could be developed to account for polarizability via changes in charge magnitude or the induction of dipoles upon movement of the probe. 

We limit the discussion to simple non-polarizable force fields in which the individual atoms carry fixed charges. They capture many-body-effects such as electronic polarization only in an effective way. More sophisticated polarizable force fields have been developed over the past two decades (see for instance Ponder et al. [2010] and references therein) however they are computationally substantially more demanding. 

An important subset of many-body potentials shown to be important for simulating interfacial systems are those referred to as polarizable force fields.Various aspects of polarizable force fields, especially for use in biomolecular modeling, is explained by Ren et al. in Chapter 3 of this volume. If one treats the fixed charges in Eq. [3] as parameters to be fitted to obtain the best agreement of the condensed phase simulations with experiments, in many cases one finds that the optimal values are considerably different from those obtained from a fit to a molecular (gas phase) dipole moment or from quantum calculations on isolated molecules. This is because in a condensed medium, the local electric field E, (at the location of a particle i) is determined by all the fixed charges and by all the induced dipoles in the system ... 

Giese TJ, York DM (2004) Many-body force field models based solely on pairwise Coulomb screening do not simultaneously reproduce correct gas-phase and condensed-phase polarizability limits. J... 

This includes the Pauli repulsion and (attractive) dispersion terms. The polarizability of the ions is included using the shell model (Dick and Overhauser, 1964) which, as discussed in Chapter 3, models the polarizability using a massive core linked to a mass-less shell by a spring. The theoretical basis of this model is uncertain, but its practical success has been attested over 20 years. Probably the best way to consider it is as a sensible model for linking the electronic polarizability of the ions to the forces exerted by the surrounding lattice. It is therefore a many-body term, a fact that should be remembered if one wishes to consider three-body potentials in the description of the crystal. A recent development in the field has been the use of quantum calculations. These are discussed in detail elsewhere (Chapter 8) but some results will be compared with the classical simulations in this chapter. 

The choice of the adjustable parameters used in conjunction with classical potentials can result to either effective potentials that implicitly include the nuclear quantization and can therefore be used in conjunction with classical simulations (albeit only for the conditions they were parameterized for) or transferable ones that attempt to best approximate the Born-Oppenheimer PES and should be used in nuclear quantum statistical simulations. Representative examples of effective force fields for water consist of TIP4P (Jorgensen et al. 1983), SPC/E (Berendsen et al. 1987) (pair-wise additive), and Dang-Chang (DC) (Dang and Chang 1997) (polarizable, many-body). The polarizable potentials contain - in addition to the pairwise additive term - a classical induction (polarization) term that explicitly (albeit approximately) accounts for many-body effects to infinite order. These effective potentials are fitted to reproduce bulk-phase experimental data (i.e., the enthalpy at T = 298 K and the radial distribution functions at ambient conditions) in classical molecular dynamics simulations of liquid water. Despite their simplicity, these models describe some experimental properties of liquid... 

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