hoomd.hpmc.pair#

Overview

LennardJones

Lennard-Jones pair potential (HPMC).

Pair

Pair potential base class (HPMC).

Details

Pair Potentials for Monte Carlo.

Define \(U_{\mathrm{pair},ij}\) for use with HPMCIntegrator, which will sum all the energy from all Pair potential instances in the pair_potentials list.

Example:

simulation.operations.integrator.pair_potentials = [pair]
class hoomd.hpmc.pair.LennardJones(default_r_cut=None, default_r_on=0.0, mode='none')#

Bases: Pair

Lennard-Jones pair potential (HPMC).

Parameters:

  • default_r_cut (float) – Default cutoff radius \([\mathrm{length}]\).

  • default_r_on (float) – Default XPLOR on radius \([\mathrm{length}]\).

  • mode (str) – Energy shifting/smoothing mode.

LennardJones computes the Lennard-Jones pair potential between every pair of particles in the simulation state. The functional form of the potential, including its behavior under shifting modes, is identical to that in the MD pair potential hoomd.md.pair.LJ.

See also

hoomd.md.pair.LJ

hoomd.md.pair

Example

lennard_jones =  hoomd.hpmc.pair.LennardJones()
lennard_jones.params[('A', 'A')] = dict(epsilon=1, sigma=1, r_cut=2.5)
simulation.operations.integrator.pair_potentials = [lennard_jones]
params#

The potential parameters. The dictionary has the following keys:

  • epsilon (float, required) - Energy well depth \(\varepsilon\) \([\mathrm{energy}]\).

  • sigma (float, required) - Characteristic length scale \(\sigma\) \([\mathrm{length}]\).

  • r_cut (float): Cutoff radius \([\mathrm{length}]\). Defaults to the value given in default_r_cut on construction.

  • r_on (float): XPLOR on radius \([\mathrm{length}]\). Defaults to the value given in default_r_on on construction.

Type: TypeParameter [tuple [particle_type, particle_type], dict]

mode#

The energy shifting/smoothing mode: Possible values are: "none", "shift", and "xplor".

Type: str

class hoomd.hpmc.pair.Pair#

Bases:

Pair potential base class (HPMC).

Pair potentials define energetic interactions between pairs of particles in hoomd.hpmc.integrate.HPMCIntegrator. Particles within a cutoff distance interact with an energy that is a function the type and orientation of the particles and the vector pointing from the i particle to the j particle center.

Note

The base class Pair implements common attributes (energy, for example) and may be used in for isinstance or issubclass checks. Pair should not be instantiated directly by users.

property energy#

Potential energy contributed by this potential \([\mathrm{energy}]\).

Typically:

\[U = \sum_{i=0}^\mathrm{N_particles-1} \sum_{j=i+1}^\mathrm{N_particles-1} U_{\mathrm{pair},ij}\]

See hoomd.hpmc.integrate for the full expression which includes the evaluation over multiple images when the simulation box is small.

Example

logger.add(obj=pair, quantities=['energy'])

(Loggable: category=”scalar”)

Type:

float

Modules