Force Fields for Molecular Simulations of Liquid Interfaces

Force Fields for Molecular Simulations of Liquid Interfaces 

In the classical molecular dynamics method, the dynamics of a system composed of N particles are followed by numerically solving the 3 N-coupled Newton equations of motion  

The simplest approach is to express the potential energy function as a sum of interactions between all pairs of particles belonging to different molecules (nonbonded interactions), plus a sum of the bonding interactions in 

This is convenient for reducing the number of needed parameters. It is also useful for establishing the so-called transferable force field in which a set of parameters are assigned to atom types that can then be used for similar molecules. 

While the pair approximation of Eq. [2] is efficient for computer simulations, a better agreement with experimental data can sometimes be achieved by utilizing more general force fields. n-Body potentials, which depend on the simultaneous positions of n particles with n 2, provide a more refined description of condensed phase systems, but only in a few cases have they been used for liquid surfaces.obvious case where three-(or higher)-body potentials are necessary is when classical MD is used to model a chemical reaction. The simple A -I- BC atom exchange reaction, for example, has been modeled with the three-body LEPS potential.The topic of potentials used to model chemical reactions will be further discussed in the section on reactivity at liquid interfaces. 

---