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[lammps-users] improper_coeff
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[lammps-users] improper_coeff


From: Hossein Geraili <geraili.hsn@...24...>
Date: Mon, 4 Sep 2017 09:57:49 +0430

Dear Lammps users,


I simulated a box of 200 of ionic liquid molecules in NVT ensemble using:

pair_style   lj/cut/coul/long  11

kspace_style pppm 1.0e-4
when I use  fix         3 all press/berendsen iso 1184 1184 100.0, it produces an "out of range atoms - cannot compute pppm", but without this fix it is ok, but the pressure data is not well-fitted.
 before the above-mentioned error there is a warning " improper problem, which below this warning for all four atoms it produces nan values".
I used topotools to produce data file, and now, I found out that one type of my molecules improper is missing. Is there any easy way to add that improper_type. Is it possible that this missing improper type would be the cause of my bad results with great Error percent compare to exp. data?

Also, I used opls for dihedral because all the dihedrals and impropers in the article that I used to extract them is in opls form, but Lammps do not have opls form for improper, so I used cvff ( because first and third and fourth coeff. of improper were zero) and convert the coeffs to cvff form. Is this wrong? 

--
Hosein Geraili Daronkola
M.Sc.Graduated of physical chemistry
Physical Chemistry,
Department of Chemistry,
Sharif University of Technology.
geraili_hosein@...7110...



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