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> Hi:
> > Two melt models were built for polyethylene (PE) and > polyvinylmethylether (PVME) melt with PBC condition . > > The density of both melt model agree with experimenal value well.But > when one check the radius of gyration (Rg) of them, both of them were > too small to accept as follows. > > The Rg for PE (C1000) is just 28 angstrom. It means the infinite > charaterastic ratio (Cinf) for the polymer is just about 2 which is much > smaller than scatter experimental value about 7. > > The Rg for PVME (C44) melt is about 6.6 angstrom. It means the Cinf for > the polymer is just 2.5 which is much smaller than scatter experimental > value 8-10. > > Can these results be accepted? > > Is there any fault in force field? gromos96a Usually a garbage result as output means that you had either garbage as input, or garbage for the algorithm. Find a published article that describes a similar simulation and adapt their method suitably. Otherwise describe your method more thoroughly (e.g. how large was the box, what ensemble did you use, equilibration regime, etc.) and maybe someone has some judgement they can share with you. Mark Hi Mark:
Thanks for your advise. Because
the PE model is built by one of my officemate, i did not konw its
details.
The cell length about my PVME
model is 4.5 nm which is big enough for a PVME chain possesses all trans
conformation. The ensemble is NVT with the control file Pcoupl = no after
10ns NPT simulation to reach the experimental density. The runtime for NVT is
5ns from which the relax time for end to end vector is anaylzed. The relax
time is about 1ns. So i think the system has been relaxed
enough.
Is there any error in my
process?
Maybe the residue parameter for
PVME is also needed for discuss. They are:
[ VME ]
[ atoms ] ; atom type charge cgnr CN Gasteiger CAB CH1 0.142 1 ; CN CAA CH2 0.035 1 ; CN OAD OE -0.352 1 ; CN CAC CH3 0.174 1 ; CN [ bonds ] ; ai aj fu CAA CAB gb_27 CAB OAD gb_53 CAC OAD gb_53 CAB +CAA gb_27 [ angles ] ; ai aj ak fu c0, c1, ... CAA CAB OAD ga_30 CAB OAD CAC ga_10 OAD CAB +CAA ga_30 CAA CAB +CAA ga_15 CAB +CAA +CAB ga_15 [ dihedrals ] ; ai aj ak al fu c0, c1, m, ... CAA CAB OAD CAC gd_13 CAA CAB +CAA +CAB gd_34 +CAA CAB OAD CAC gd_13 CAB +CAA +CAB +OAD gd_1 *************************************************
Ji Qing Institute of Chemistry, Chinese Academy of Sciences Tel: 0086-10-62562894 ，82618423 ************************************************* |
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