AMBER Archive (2008)

Subject: Re: AMBER: Build a MPI NAB

From: David A. Case (
Date: Wed Apr 09 2008 - 11:27:28 CDT

On Wed, Apr 09, 2008, Hu, Shaowen (JSC-SK)[USRA] wrote:
> I have another question. Is there a simple relation between saltcon in
> AMBER and kappa in NAB?

You can Google to find lots of derivations of Debye-Huckel theory, or look in
standard textbooks. In brief:

    kappa**2 = (8 pi beta I)/epsilon, where I is the ionic strength, which is
the same as concentration for a 1-1 salt. Taking T=298.15 and epsilon=78.5,

    kappa = sqrt( 0.10806d0 * saltcon )

where kappa is in Ang**-1 and saltcon is in mol/l. Hence, for a 1-1 saltcon
of 0.1 M, kappa is about 0.10395.

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