[gmx-users] vdw radii in g_sas

Justin Lemkul jalemkul at vt.edu
Fri May 9 18:53:58 CEST 2014

On 5/9/14, 12:23 PM, rajat desikan wrote:
> Hi All,
> In the local copy of vdwradii.dat for g_sas calculations, the vdw radii are
> very approximate.
> Eg. C = 0.15 nm in vdwradii.dat, whereas ffnonbonded says sigma = 0.367 nm
> => vdwradius=0.185 nm
> Is it prudent to replace the values in the local vdwradii.dat with the
> vdwradii derived from ffnonbonded values? I would love to hear your
> thoughts/suggestions.

No.  The value of sigma will not give you the van der Waals radius of an atom. 
For each force field, the value is different, and it is based on optimized 
intermolecular distances.  I don't think there's a clear way to turn this into 
some measure of an atom's size.

If you're concerned that the values in vdwradii.dat are not sufficiently 
accurate, replace them with real experimentally determined values.



Justin A. Lemkul, Ph.D.
Ruth L. Kirschstein NRSA Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 601
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

jalemkul at outerbanks.umaryland.edu | (410) 706-7441


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