AMBER Archive (2006)

Subject: Re: AMBER: use_pme=0 problem

From: luckyang_at_gmail.com
Date: Thu May 25 2006 - 12:09:59 CDT


Dear Dr. Case,

I may have to keep the longrange VDW correction term. Does this mean I have
to turn the PME on? Is there a way to keep the longrange VDW correction
while turn off the PME? The difference of the computer time is huge with and
without PME for my systems.

Thanks for your help,

Lu

On 5/24/06, luckyang_at_gmail.com <luckyang_at_gmail.com> wrote:
>
> Dear Dr. Case,
>
> Thank you very much for your help. It gives me the same results if I set
> "vdwmeth = 0". I will check the TraPPE paper for the right option of these
> flags.
>
> All the best.
>
> Lu
>
> On 5/24/06, David A. Case <case_at_scripps.edu> wrote:
>
> > On Wed, May 24, 2006, luckyang_at_gmail.com wrote:
> > >
> > > I have identified the source of the difference. The main difference
> > comes
> > > from the EVDW term. How does use_pme affect VDW energy? In attachment
> > please
> > > find the file contains the differences.
> >
> > My best guess is the the longrange vdw correction term is a part of the
> > "PME"
> > code, so that you are getting this in one calculation but not the other.
> > Try setting vdwmeth=0 in both runs to see if you get the same results.
> >
> > I don't know if your force field was parameterized assuming such a long
> > range
> > correction or not. Leaving it out would lead to a slight change in the
> > density of the system, but it would depend on the force field to know
> > which
> > one is "better".
> >
> > ...dac
> >
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>
>

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