angle

Angle force classes apply a force and virial on every particle in the simulation state commensurate with the potential energy:

$$U_\mathrm{angle} = \sum_{(i,j,k) \in \mathrm{angles}} U_{ijk}(\theta)$$

Each angle is defined by an ordered triplet of particle tags in the hoomd.State member angle_group. HOOMD-blue does not construct angle groups, users must explicitly define angles in the initial condition.

In the angle group (i,j,k), $\theta$ is the angle between the vectors $\vec{r}_{ij}$ and $\vec{r}_{kj}$.

Angle force classes assign 1/3 of the potential energy to each of the particles in the angle group:

$$U_l = \frac{1}{3} \sum_{(i,j,k) \in \mathrm{angles}} U_{ijk}(\theta) [l=i \lor l=j \lor l=k]$$

and similarly for virials.

Classes

• Angle
• CosineSquared
• Harmonic
• Table