LJ¶

class hoomd.md.special_pair.LJ¶

Bases: SpecialPair

LJ special pair force.

LJ computes forces, virials, and energies on all special pairs in the simulation state with:

\[\begin{split}U(r) = \begin{cases} 4 \varepsilon \left[ \left( \frac{\sigma}{r} \right)^{12} - \left( \frac{\sigma}{r} \right)^{6} \right] & r < r_{\mathrm{cut}} \\ 0 & r \ge r_{\mathrm{cut}} \\ \end{cases}\end{split}\]

Note

Use LJ to implement special 1-4 interactions in atomistic force fields, such as the scaled 1-4 interactions in OPLS where both the 1-4 LJ and Coulomb interactions are scaled by 0.5.

Examples:

lj = special_pair.LJ()
lj.params['cluster'] = dict(epsilon=3, sigma=0.5)
lj.r_cut['cluster'] = 5

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 LJ:

params¶

The parameter of the lj forces for each particle type. The dictionary has the following keys:

epsilon (float, required) - energy parameter \([\mathrm{energy}]\)
sigma (float, required) - particle size \([\mathrm{length}]\)

Type:: TypeParameter[special pair type, dict]

r_cut¶

The cut-off distance for special pair potential \([\mathrm{length}]\)

Type:: TypeParameter[special pair type, float]