Zetterling

class hoomd.hpmc.pair.Zetterling(default_r_cut=None, default_r_on=0.0, mode='none')

Bases: Pair

Zetterling pair potential (HPMC).

Parameters:

• default_r_cut (float) – Default cutoff radius $[\mathrm{length}]$.

• default_r_on (float) – Default XPLOR on radius $[\mathrm{length}]$.

• mode (str) – Energy shifting/smoothing mode.

Zetterling computes the oscillating pair potential between every pair of particles in the simulation state. The functional behavior of the potential under the various shifting modes is the same as in hoomd.md.pair.

$$U(r) = A \frac{\exp{(\alpha r)\cos{(2 k_F r)}}}{r^3} + B \left( \frac{\sigma}{r} \right)^n$$

The potential was introduced in F. H. M. Zetterling, M. Dzugutov, and S. Lidin 2001.

Example

zetterling = hoomd.hpmc.pair.Zetterling(mode="shift")
zetterling.params[("A", "A")] = {
    "A": 1.58,
    "alpha": -0.22,
    "kf": 4.12,
    "B": 0.95533,
    "sigma": 1.0,
    "n": 18.0,
    "r_cut": 2.649,
}

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Members inherited from Pair:

property energy

Potential energy contributed by this potential $[\mathrm{energy}]$. Read more...

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Members defined in Zetterling:

params

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

• A (float, required) - Energy scale of the first term $A$ $[\mathrm{energy}]$

• alpha (float, required) - Screening factor lpha $[\mathrm{length}^{-1}]$

• kf (float, required) - Wave number to mimic the Friedel oscillations effect $k_F$ $[\mathrm{length}^{-1}]$.

• B (float, required) - Energy scale of the second term $B$ $[\mathrm{energy}]$.

• sigma (float, required) - Repulsive core size $\sigma$ $[\mathrm{length}]$

• n (float, required) - The power to take sigma/r in the second term $n$ $[\mathrm{dimensionless}]$

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

mode

The energy shifting/smoothing mode: Possible values are: "none", "shift", and "xplor".

Example

zetterling.mode = "shift"

Type: str