[gmx-users] force fileds gromos and oplsaa
jalemkul at vt.edu
Thu Nov 16 14:31:28 CET 2017
On 11/16/17 8:28 AM, Faezeh Pousaneh wrote:
> sorry for silly question, but I did not find my answer by searching.
> In gromos force fields, the file nonbonded.itp includes nonbonded
> parameters for two different atoms, e.g
> C O 1 2.300953E-03 2.222000E-06
> while I do not see oplsaa provides parameters for nonbonded interactions of
> different atoms, why?
The [nonbond_params] section specifies atom pairs for which normal
combination rules do not apply, e.g. pair-specific Lennard-Jones
parameters (CHARMM calls these NBFIX, for instance).
Some force fields use them, others don't (and calculate everything via
combination rules). In the case of OPLS-AA, there are a huge number of
atom types, more than any other force field (AFAIK), which is
essentially doing the same thing - there are highly specific parameter
optimizations for given interactions.
Justin A. Lemkul, Ph.D.
Virginia Tech Department of Biochemistry
303 Engel Hall
340 West Campus Dr.
Blacksburg, VA 24061
jalemkul at vt.edu | (540) 231-3129
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