Advancement of MD Methods

Advancement of MD Methods 2.4.1. Empirical Valence Bond Models 

Valence bond (VB) theories or empirical valence bond (EVB) methods have been developed in order to solve this problem with bond potential functions that (i) allow the change of the valence bond network over time and (ii) are simple enough to be used efficiently in an otherwise classical MD simulation code. In an EVB scheme, the chemical bond in a dissociating molecule is described as the superposition of two states a less-polar bonded state and an ionic dissociated state. One of the descriptions is given by Walbran and Kornyshev in modeling of the water dissociation process.4,5 As 

The dynamics of this low-mass charged site provides an inertialess polarizability, intended to mimic the electronic polarizability of the frequency domain higher than the O-H stretch frequency. This feature is very similar to that of ab initio methods. 

Goddard et al. developed and validated the reactive force field (ReaxFF) to describe complex reactions (including catalysis) nearly as accurately as QM in some cases but at computational effort comparable to classical molecular dynamics (MD).10,18 Similar to empirical non-reactive force fields, the reactive force field divides the system energy up into various partial energy contributions, 

A fundamental assumption of ReaxFF is that the bond order BOy between a pair of atoms can be obtained directly from the interatomic distance rtj as given in Eq. (27). 

---