On 1/2/13 10:14 AM, Bogdan Costescu wrote:
On Wed, Jan 2, 2013 at 2:58 PM, James Starlight <jmsstarli...@gmail.com> wrote:
By the way now I'd like to simulate the same 2D flexible ( in non
planar hybridization) lattice but consist of non-hydrogens atoms only
( only atoms forming lattice scaffold ). Does it possible to change
Carbon atom-valence (from 4 to 3) preventing tetragonal-like geometry
( >c- ) or should I use anothe atom type for such lattice ?

I can't imagine how it can be both "non planar hybridization" and
"preventing tetragonal-like geometry", but maybe I don't understand
your intentions. Assuming you do want a change in geometry - from
tetragonal to planar - then you need to use different parameters to
describe the different geometry, it's not only about changing valence.
If you use OPLS-AA, this means a change of atom type from something
like C sp3 (f.e. opls_139) to sp2 (f.e. opls_147) - both these types
chosen for having zero charge.


One must use the right atom type (for LJ purposes) in conjunction with correct bonded parameters. You can create whatever monster atom you choose with any arbitrary valence, as long as you create the right bonded parameters that govern its geometry. Since MD simulations don't explicitly consider valence, you can do whatever you want, in theory.

-Justin

--
========================================

Justin A. Lemkul, Ph.D.
Research Scientist
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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