Angle Functions

Functional forms for angle interactions

Below are listed the interaction forms available for angles within molecules, with energy and force equations provided in full. Parameters are listed in the input order expected by Dissolve.

Angle interaction between atoms i, j and k, where the bond angle is θijk.

Note that within input files any equilibrium angles θeq should be provided in degrees, but the equations as written below work internally in radians.

Force equations are derived by applying the chain rule, and where

dθdcosθ=1sinθ

Keyword Parameters Description
Harmonic k
θeq
Simple harmonic angle bend Eijk=12k(θijkθeq)2 Fijk=dθdcosθk(θijkθeq)
Cosine k
n
θeq
s
Cosine angle bend with periodicity n Eijk=k(1+scos(nθijkθeq)) Fijk=dθdcosθknssin(nθijkθeq)
Cos2 k
C0
C1
C2
Double cosine angle potential Eijk=k(C0+C1cos(θijk)+C2cos(2θijk)) Fijk=dθdcosθk(C1sin(θijk)+2C2sin(2θijk))
Last modified February 24, 2023: Docs 1.0 (#1221) (6f6c04b7e)