espressopp.interaction.FENECapped¶
A capped FENE potential avoiding calculation of unreasonably large bonded forces. It is usually applied at the
equilibration stage of a simulation and helps a polymer system to relax. After the system has reached
its equilibrium the capped potential should be substituted by a regular FENE, espressopp.interaction.FENE.
The capped FENE potential is employed as:
\[U = -\frac{1}{2}r_{max}^2 K \cdot
log \left[1 - \left(\frac{D - r_0}{r_{max}}\right)^2\right],\]
where
\[D = min \left(r, r_{\it{cap}}\right).\]
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class
espressopp.interaction.FENECapped(K = 30.0, r0 = 0.0, rMax = 1.5, cutoff = inf, r_cap = 1.0, shift = 0.0)¶ Parameters: - K (real) – attractive force strength (in \(\epsilon / \sigma^2\) units)
- r0 (real) – displacement parameter (in \(sigma\) units)
- rMax (real) – size parameter (in \(sigma\) units)
- cutoff (real) – cutoff radius
- r_cap (real) – radius of capping (in \(sigma\) units)
- shift (real) – shift of the potential
After setting up the potential you have to apply it to the particles in the pair list (bondlist):
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class
espressopp.interaction.FixedPairListFENECapped(system, bondlist, potential)¶ Parameters: - system (object) – system object
espressopp.System() - bondlist (list) – list of bonds
espressopp.FixedPairList() - potential (object) – bonded potential, in this case
espressopp.interaction.FENECapped()
Methods
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getFixedPairList()¶ Return type: A Python list of pairs (the bondlist)
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getPotential()¶ Return type: potential object
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setFixedPairList(bondlist)¶ Parameters: bondlist (list) – fixed-pair list (bondlist)
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setPotential(potential)¶ Parameters: potential (object) – a potential applied to all pairs in the bondlist
- system (object) – system object
Example of usage
>>> Please, refer to the example of FENE potential
Go to FENE-example espressopp.interaction.FENE