[gmx-developers] Problems with artificial minima when using soft-core potentials

[Alan E. Mark]

A number of people have noted potential problems with the way the 
solft-core potential is implemented in GROMACS.

Specifically if the same parameters are used for the soft-core for both 
LJ and electrostatic interactions this gives rise to temporary minima at 
intermediate lambda values.

That using a single value for both the LJ and Coulombic interactions 
would give rise to this problem was recognized in the original paper of 
Beutler et al.    http://dx.doi.org/10.1016/0009-2614(94)00397-1

The simple and logical solution to this problem is simply to introduce 
separate alpha values for the LJ and Coulombic interactions. That is to 
use the form of the soft-core that was proposed originally. If the alpha 
value for the charge is set larger than that of the LJ these artificial 
minima no longer occur.

Alan Mark and Alpesh Malde

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____________________________________________________________________
Prof. Alan E. Mark

BRISBANE
Molecular Dynamics Group
School of Chemistry and Molecular Biosciences (SCMB)
University of Queensland
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