OPLS¶

class hoomd.md.dihedral.OPLS¶

Bases: Dihedral

OPLS dihedral force.

OPLS computes forces, virials, and energies on all dihedrals in the simulation state with:

U(\phi) = \frac{1}{2}k_1 \left( 1 + \cos\left(\phi \right) \right) + \frac{1}{2}k_2 \left( 1 - \cos\left(2 \phi \right) \right) + \frac{1}{2}k_3 \left( 1 + \cos\left(3 \phi \right) \right) + \frac{1}{2}k_4 \left( 1 - \cos\left(4 \phi \right) \right)

$k_n$ are the force coefficients in the Fourier series.

Examples:

opls = dihedral.OPLS()
opls.params["A-A-A-A"] = dict(k1=1.0, k2=1.0, k3=1.0, k4=1.0)

Members inherited from AutotunedObject:

property is_tuning_complete¶: Check if kernel parameter tuning is complete. Read more...

Members inherited from Force:

additional_virial¶: Additional virial tensor term $W_\mathrm{additional}$ . Read more...

energy¶: The potential energy $U$ of the system from this force. Read more...

torques¶: The torque $\vec{\tau}_i$ applied to each particle. Read more...

virials¶: Virial tensor contribution $W_i$ from each particle. Read more...

Members defined in OPLS:

params¶

The parameter of the OPLS bonds for each particle type. The dictionary has the following keys:

k1 (float, required) - force constant of the first term $[\mathrm{energy}]$
k2 (float, required) - force constant of the second term $[\mathrm{energy}]$
k3 (float, required) - force constant of the third term $[\mathrm{energy}]$
k4 (float, required) - force constant of the fourth term $[\mathrm{energy}]$