Bond order potential

Bond order potential is a class of empirical (analytical) interatomic potentials which is used in molecular dynamics and molecular statics simulations.

[5] They have the advantage over conventional molecular mechanics force fields in that they can, with the same parameters, describe several different bonding states of an atom, and thus to some extent may be able to describe chemical reactions correctly.

It is based on the Linus Pauling bond order concept [1] [6] and can be written in the form This means that the potential is written as a simple pair potential depending on the distance between two atoms

, but the strength of this bond is modified by the environment of the atom

is a function that in Tersoff-type potentials depends inversely on the number of bonds to the atom

which corresponds to the strongest and shortest possible bond.

The other limiting case, for increasingly many number of bonds within some interaction range,

and the potential turns completely repulsive (as illustrated in the figure to the right).

Alternatively, the potential energy can be written in the embedded atom model form where

These two forms for the energy can be shown to be equivalent (in the special case that the bond-order function

[7] A more detailed summary of how the bond order concept can be motivated by the second-moment approximation of tight binding and both of these functional forms derived from it can be found in.

These pi-bond contributions to the sigma bond order are responsible to stabilize the asymmetric before the symmetric (2x1) dimerized reconstruction of the Si(100) surface.