Hi,
I used LAMMPS for crosslinking DGEBA(Epoxy) and DETA(Resin). I have packed 80 DGEBA and 32 DETA molecules in a 46A box. I used the CHARMM force field and the parameters were generated from swissparam.ch.
I minimized and then equillibrated using 50ps NVT and then 400ps NPT at 600K and few other lower temperatures. Then,I used the fix bond/create command to crosslink the molecules. Finally the 600 K system was cooled stepwise for 2ns at each step at intervals of 15 K to 300 K. The glass transition temperature and other thermo-mechanical properies were found out from the density Vs temperature curve.
The density of the system at 300 K came out to be 1.221 gm/cm3
Is the force field I am using right for the phenomenon I want to simulate??
A couple of points:
a) I would check that the cross-linking left the system with
well-defined bonds, angles, dihedrals, etc and that proper
force-field params are assigned to all of them.
b) you have an overall small system, few dozen molecules.
Doing NPT and getting a density for such a system can
easily be off. You could try doing different sizes to
see if there are finite–size effects.
Steve
Thank you Mr. Steve…
After crosslinking, topology and charge update was done.
I would like to know if CHARMM force field is the correct one to be used for such type of work.
I will try with different sizes also…
Dhritiman
I suggest looking in the literature to see
what ffields have been used for this kind of system.
Steve
Thank you Mr. Steve…
After crosslinking, topology and charge update was done.
I would like to know if CHARMM force field is the correct one to be used for such type of work.
Search the literature to get confirmation on this. Or make some validation tests, that confirm it. If you’ve never done MD or never used charmm as a force field before, it is compulsory to do this. You cannot write in a paper: some guy told me that it was OK.
Axel
Thanks to all…
The website from which r=the parameters were obtained said that they are for drug design.
I tried to use dreiding force field since i read in a paper that it was used for this purpose… AMBER has also been used… With Dreiding it is not working.
Bond atoms or Dihedral atoms missing on proc**
Dhritiman