On 8/18/17 3:43 AM, Ming Tang wrote:
Dear all,
I want to calculate sigma for OPLSAA.ff from C6 developed based on
GROMOS54a7.ff.
From the manual, I got the equations:
C12 = Sigma^(6)*C6
C6 = 4*sigma^(6)*epsilon
However, I found sigma and epsilon are different in OPLSAA and AMBER, and that
C6 from GROMOS and sigma from OPLSAA do not match these equations.
Could anybody give me some guidance?
Mathematically speaking, you can certainly transform one to another, but
you shouldn't do it. GROMOS parameters aren't guaranteed to mix with
any other force field, so convention wisdom is to not waste time trying
to do it. Force fields are self-consistent entities. Mixing and
matching yields a physical model of unknown (likely junk) quality.
-Justin
--
==
Justin A. Lemkul, Ph.D.
Assistant Professor
Virginia Tech Department of Biochemistry
303 Engel Hall
340 West Campus Dr.
Blacksburg, VA 24061
jalem...@vt.edu | (540) 231-3129
http://www.biochem.vt.edu/people/faculty/JustinLemkul.html
==
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