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]