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 kernel_parameters¶: Kernel parameters. Read more...

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

tune_kernel_parameters()¶: Start tuning kernel parameters. Read more...

Members inherited from Force:

additional_energy¶: Additional energy term. Read more...

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

cpu_local_force_arrays¶: Local force arrays on the CPU. Read more...

energies¶: Energy contribution \(U_i\) from each particle. Read more...

energy¶: The potential energy \(U\) of the system from this force. Read more...

forces¶: The force \(\vec{F}_i\) applied to each particle. Read more...

gpu_local_force_arrays¶: Local force arrays on the GPU. 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 \([\mathrm{energy}]\)

Type:: TypeParameter [dihedral type, dict]