As the paper said,
"For the classical Kremer and Grest (KG) model, only a repulsive force is employed, i.e., Rc = 2^(1/6)σ. Such a model is close to an athermal model of polymer, lacking the ability to predict the glass transition driven by temperature. Furthermore, some simulation results reveal a negative thermal expansion coefficient without attraction."
Because I want to predict the Tg, I think the cutoff should be 2.5sigma. I think I should add the fene+lj bond on my own. Do you have some better ideas?
In addition, Do you mean that you would use WCA between all the polymer beads?
Thanks so much!
Best regards!
Ricky
Date: 2019-05-21 20:59
Subject: Re: [ESPResSo-users] FENE+LJ bond
Actually, they did not specify in the paper for which pairs of particles they used the usual LJ potential (Eq.1). They only say that the fene + LJ (WCA) with cut=2^1/6 sigma) is used for polymer-polymer interactions. The text suggests that they used Eq.1 for all particle pairs including the polymer but that would be a very wierd setting.
If you need to model exactly the same system, then I think that you should ask the authors for clarification. Otherwise, I would use WCA potential for polymer-polymer and LJ with cut=2.5sigma fro all other pairs.
Greetings,
peter
Hi, isn't that a cutoff for the attractive potential to model magnetic particles only? Sorry, I don't know the papers, just suggesting
Dear Peter,
Actually, in the paper, the cutoff distance of LJ potential between nonbonded beads is 2.5[sigma] while the cutoff distance of LJ potential between bonded beads is 2^(1/6)[sigma]. This can't be done by your way.
Thanks anyway!
Regards!
Ricky
Date: 2019-05-21 20:44
Subject: Re: [ESPResSo-users] FENE+LJ bond
Hi Ricky,
Just set up a FENE potential between the given pair of particles, and an LJ potential between the given particle types (probably the same type) and you get exactly what you want. This is the standard setup which is just described in a weird way in the paper that you cited.
The fene potential acts just between the two particles with a given id. The LJ potential acts between any pair of particles. If your pair of particles interacts both with fene and LJ, then you get the fene+LJ interaction.
See also the script minimal-polymer.py in the samples directory.
peter
Dear Sebastian,
Thanks for your reply at first!
I want to model the hard-soft block copolymers with magnetic particles and the copolymer model I use is from this paper
I will use the FENE+LJ bond with bonded beads and the LJ potential with nonbonded beads.
Regards!
Ricky
--
Dr. Peter Košovan
Department of Physical and Macromolecular Chemistry
Faculty of Science, Charles University in Prague, Czech Republic
Katedra fyzikální a makromolekulární chemie
Přírodovědecká fakulta Univerzity Karlovy v Praze
www.natur.cuni.cz/chemistry/fyzchem/Tel. +420221951029
Fax +420224919752
--
_____________________
Polymer Institute of the Slovak Academy of Sciences
Dubravska cesta 3
845 41 Bratislava, Slovak Republic [‡]
tel: +421 2 3229 4321
--
Dr. Peter Košovan
Department of Physical and Macromolecular Chemistry
Faculty of Science, Charles University in Prague, Czech Republic
Katedra fyzikální a makromolekulární chemie
Přírodovědecká fakulta Univerzity Karlovy v Praze
www.natur.cuni.cz/chemistry/fyzchem/Tel. +420221951029
Fax +420224919752