Re: Mirror Image Energy Discrepency

From: Jérôme Hénin (jhenin_at_ifr88.cnrs-mrs.fr)
Date: Wed Feb 09 2011 - 14:40:06 CST

Hi Keith,

CHARMM dihedral energy terms are symmetric iff the phase parameter
delta is 0 or 180 degrees. Which it is, at least in the standard
peptide force field.
I've just run a test with a small peptide, and got exactly the same
result. How did you prepare the input coordinates?

Best,
Jerome

On 9 February 2011 20:23, Keith Battle <keith.battle_at_gmail.com> wrote:
> Hi NAMD world,
>
> I performed a minimization using the CHARMM force field of a single
> L-Aspartate in vacuum using NAMD 2.7. I also performed the same
> minimization of a single D-Aspartate. On the 0th step, the total
> energy and the dihedral energy are different by about 7 kcal/mol. All
> other energies are the same (bond, elec, etc.). Are there any ideas as
> to why this may be the case? I performed the same procedure in QUANTA
> with the CHARMM force field and the total energy for L and D are the
> same.
>
> Best,
>
> Keith Battle
> Research Technician
> University of South Alabama
>
>

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