ZBL

class hoomd.md.pair.ZBL(nlist, default_r_cut=None, default_r_on=0.0)

Bases: Pair

ZBL pair force.

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 $[\mathrm{length}]$.

ZBL computes the Ziegler-Biersack-Littmark pair force on every particle in the simulation state:

$$U(r) = \frac{Z_i Z_j e^2}{4 \pi \epsilon_0 r_{ij}} \left[ 0.1818 \exp \left( -3.2 \frac{r_{ij}}{a_F} \right) \right. \\ + 0.5099 \exp \left( -0.9423 \frac{r_{ij}}{a_F} \right) \\ + 0.2802 \exp \left( -0.4029 \frac{r_{ij}}{a_F} \right) \\ + \left. 0.02817 \exp \left( -0.2016 \frac{r_{ij}}{a_F} \right) \right]$$

Where each parameter is defined as:

• $Z_i$ - Z_i - Atomic number of species i $[\mathrm{dimensionless}]$

• $Z_j$ - Z_j - Atomic number of species j $[\mathrm{dimensionless}]$

• $e$ - elementary_charge - The elementary charge $[\mathrm{charge}]$

• $a_F = \frac{0.8853 a_0}{ Z_i^{0.23} + Z_j^{0.23} }$, where $a_0$ is the Bohr radius $[\mathrm{length}]$

Example:

nl = nlist.Cell()
zbl = pair.ZBL(default_r_cut=3.0, nlist=nl)

Zi = 54
Zj = 7
e = 1
a0 = 1
aF = 0.8853 * a0 / (Zi**(0.23) + Zj**(0.23))

zbl.params[('A', 'B')] = dict(qi=Zi*e, qj=Zj*e, aF=aF)

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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...

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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...

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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...

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Members defined in ZBL:

params

The ZBL potential parameters. The dictionary has the following keys:

• q_i (float, required) - $q_i=Z_i \frac{e}{\sqrt{4 \pi \epsilon_0}}$ $[\mathrm{charge}]$

• q_j (float, required) - $q_j=Z_j \frac{e}{\sqrt{4 \pi \epsilon_0}}$ $[\mathrm{charge}]$

• a_F (float, required) - $a_F = \frac{0.8853 a_0}{ Z_i^{0.23} + Z_j^{0.23} }$ $[\mathrm{length}]$

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