FENEWCA¶

class hoomd.md.bond.FENEWCA¶

Bases: Bond

FENE and WCA bond force.

FENEWCA computes forces, virials, and energies on all bonds in the simulation state with:

\[V(r) = - \frac{1}{2} k r_0^2 \ln \left( 1 - \left( \frac{r - \Delta}{r_0} \right)^2 \right) + U_{\mathrm{WCA}}(r)\]

where

\[\begin{split}U_{\mathrm{WCA}}(r) = \begin{cases} 4 \varepsilon \left[ \left( \frac{\sigma}{r - \Delta} \right)^{12} - \left( \frac{\sigma}{r - \Delta} \right)^{6} \right] + \varepsilon & r-\Delta < 2^{\frac{1}{6}}\sigma\\ 0 & r-\Delta \ge 2^{\frac{1}{6}}\sigma \end{cases}\end{split}\]

, \(k\) is the attractive force strength, \(r_0\) is the size of the bond, \(\varepsilon\) is the repulsive interaction energy, and \(\sigma\) is the repulsive interaction width.

Examples:

fenewca = bond.FENEWCA()
fenewca.params['A-A'] = dict(k=3.0, r0=2.38, epsilon=1.0, sigma=1.0,
                             delta=0.0)
fenewca.params['A-B'] = dict(k=10.0, r0=1.0, epsilon=0.8, sigma=1.2,
                             delta=0.0)

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 FENEWCA:

params¶

The parameter of the FENEWCA potential bonds. The dictionary has the following keys:

k (float, required) - attractive force strength \(k\) \([\mathrm{energy} \cdot \mathrm{length}^{-2}]\).
r0 (float, required) - size parameter \(r_0\) \([\mathrm{length}]\).
epsilon (float, required) - repulsive force strength \(\varepsilon\) \([\mathrm{energy}]\).
sigma (float, required) - repulsive force interaction width \(\sigma\) \([\mathrm{length}]\).
delta (float, required) - radial shift \(\Delta\) \([\mathrm{length}]\).

Type:: TypeParameter[bond type, dict]