DLVO¶

class hoomd.md.pair.DLVO(nlist, default_r_cut=None, default_r_on=0.0, mode='none')¶

Bases: Pair

DLVO colloidal interaction.

Parameters:

nlist (hoomd.md.nlist.NeighborList) – Neighbor list.
default_r_cut (float) – Default cutoff radius $[\mathrm{length}]$ .
default_r_on (float) – Default turn-on radius $[\mathrm{length}]$ .
name (str) – Name of the force instance.
mode (str) – Energy shifting mode.

DLVO computes the DLVO dispersion and electrostatic interaction pair force on every particle in the simulation state with:

\begin{split} V_{\mathrm{DLVO}}(r) = &- \frac{A}{6} \left[ \frac{2a_1a_2}{r^2 - (a_1+a_2)^2} + \frac{2a_1a_2}{r^2 - (a_1-a_2)^2} \\ + \log \left( \frac{r^2 - (a_1+a_2)^2}{r^2 - (a_1-a_2)^2} \right) \right] \\ & + \frac{a_1 a_2}{a_1+a_2} Z e^{-\kappa(r - (a_1+a_2))} \end{split}

where $a_1$ is the radius of first particle in the pair, $a_2$ is the radius of second particle in the pair, $A$ is the Hamaker constant, $Z$ is proportional to the surface electric potential, and $\kappa$ is the screening parameter.

The first term corresponds to the attractive van der Waals interaction with and the second term to the repulsive double-layer interaction between two spherical surfaces. See “Intermolecular and Surface Forces” Israelachvili 2011, pp. 317.

Example:

nl = hoomd.md.nlist.Cell()
dlvo = hoomd.md.pair.DLVO(nlist=nl)
dlvo.params[('A', 'A')] = dict(A=1.0, kappa=1.0, Z=2, a1=1, a2=1)
dlvo.params[('A', 'B')] = dict(A=2.0, kappa=0.5, Z=3, a1=1, a2=3)
dlvo.params[('B', 'B')] = dict(A=2.0, kappa=0.5, Z=3, a1=3, a2=3)

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 inherited from Pair:

nlist¶: Neighbor list used to compute the pair force. Read more...

mode¶: Energy smoothing/cutoff mode. Read more...

r_cut¶: Cuttoff radius beyond which the energy and force are 0. Read more...

r_on¶: Radius at which the XPLOR smoothing function starts. Read more...

compute_energy()¶: Compute the energy between two sets of particles. Read more...

Members defined in DLVO:

params¶

The potential parameters. The dictionary has the following keys:

A (float, required) - Hamaker constant $A$ $[\mathrm{energy}]$
a1 (float, required) - Radius of first particle $a_1$ $[\mathrm{length}]$
a2 (float, required) - Radius of second particle $a_2$ $[\mathrm{length}]$
kappa (float, required) - screening parameter $\kappa$ $[\mathrm{length}^{-1}]$
Z surface electric potential (float, required) - $Z$ $[\mathrm{energy} \cdot \mathrm{length}^{-1}]$

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