[gmx-users] Generalized-Reaction-Field; epsilon_r
spoel at xray.bmc.uu.se
Wed Dec 18 07:46:08 CET 2002
On Wed, 2002-12-18 at 05:49, Dr. Y. U. Sasidhar wrote:
> Generalized reaction field with Coulomb cut-off *rcoulomb*, where
> *rcoulomb* >= *rvdw* >= *rlist*. The dielectric constant beyond the
> cut-off is *epsilon_r*.
> What are the values to be used for epsilon_r consistent with spc and
> tip3p water models ?
> I remember reading recently in a paper that for tip3p you need to
> use epsilon of 54, not 80.
The rationale behind that it would seem, is that you'd have more
TIP3P/SPC beyond the cut-off, rather than more water. Although such a
choice can be defended, there is no compelling physical argument for it.
Furthermore the difference is small. I prefer 80, but then I stopped
using RF, and use PME only.
Dr. David van der Spoel, Biomedical center, Dept. of Biochemistry
Husargatan 3, Box 576, 75123 Uppsala, Sweden
phone: 46 18 471 4205 fax: 46 18 511 755
spoel at xray.bmc.uu.se spoel at gromacs.org http://xray.bmc.uu.se/~spoel
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