[gmx-users] Normal mode eigenvalue units, nm^-2 ??

[Berk Hess]

>From: Nguyen Hoang Phuong <phuong at theochem.uni-frankfurt.de>
>Reply-To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>Subject: Re: [gmx-users] Normal mode eigenvalue units, nm^-2 ??
>Date: Wed, 18 May 2005 17:08:11 +0200 (MEST)
>
>
>
> > In order to extract a frequency for a normal mode (re: eq 3.66 of the
> > Gromacs manual) I'd like to know what unit the eigenvalues are in.
> > My guess is nm^-2, which would sort of be consistent with other Gromacs
> > units, but I couldn't find explicit confirmation in the manual.
> >
> >   Marc
>yes if you are using non-mass-weighted NMA, otherwise the unit is
>(nm* (unit of mass))^-2

No!

As eq 3.66 says, it is a frequency to the power -2.
The unit is ps^-2 for mass-weighted,
amu ps^-2 for non mass weighted.

In the CVS code it is cm^-1, which is written in the xvg file.

Berk.

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