OPLS force field

The optimized potentials for liquid simulations (OPLS) force-field was developed for the simulation of proteins and other organic liquids.

OPLS-all atom

(OPLS-AA)

Form of the force field

Bond stretching

$E_{\mathrm{b}\mathrm{o}\mathrm{n}\mathrm{d}}={\sum }_{\mathrm{b}\mathrm{o}\mathrm{n}\mathrm{d}\mathrm{s}}{K}_r{(r-r_{eq})}^2$

Angle bending

$E_{\mathrm{a}\mathrm{n}\mathrm{g}\mathrm{l}\mathrm{e}}={\sum }_{\mathrm{a}\mathrm{n}\mathrm{g}\mathrm{l}\mathrm{e}\mathrm{s}}{K}_{\theta }{(\theta -{\theta }_{eq})}^2$

Torsion

$E(\varphi )=\frac{V_1}{2}[1+\cos (\varphi +f1)]+\frac{V_2}{2}[1-\cos (2\varphi +f2)]+\frac{V_3}{2}[1+\cos (3\varphi +f3)]$

Non-bonded

$E_{ab}=\sum _i^{\mathrm{o}\mathrm{n}\mathrm{a}}\sum _j^{\mathrm{o}\mathrm{n}\mathrm{b}}[\frac{q_i{q}_j{e}^2}{r_{ij}}+4{ϵ}_{ij}(\frac{\underset{ij}{\overset{12}{\sigma }}}{r_{ij}^{12}}-\frac{\underset{ij}{\overset{6}{\sigma }}}{r_{ij}^6})]f_{ij},f_{ij}=\{\begin{array}{ccc}0.5& ;& i,j=1,4\\ 1& ;& \end{array}$