[gmx-developers] ewald shift question

[Harold Park]

Dear Gromacs Developers:

My student and I are currently trying to use Gromacs 4.0.5 to perform  
some electrostatic analysis of nanostructures.  One of our goals is to  
implement the method of Dieter Wolf et al. (D. Wolf, P. Keblinski,  
S.R. Phillpot and J. Eggebrecht, Journal of Chemical Physics 1999;  
110:8254-8282) to calculate the Coulombic energy for ionic systems,  
such that the periodicity assumptions inherent in the Ewald-type  
approaches can be avoided.

In older versions of Gromacs, it appeared that there was a  
shiftLR_correction implemented as one option to calculate the  
Coulombic energies.  However, in 4.0.5, we have found code in  
ewald_util.c and ewald.c which should correspond to that for  
shiftLR_correction, but we find that these functions are not actually  
called when using the shiftLR_correction option.  Modifying the  
shiftLR_correction option is the best for us since the functional  
forms of the Coulomb energy in the Wolf method is quite similar to  
these.

Thus, I was wondering:
(1) Is the shiftLR_correction option obsolete in Gromacs 4.0.5?
(2) If so, what would be the best way to implement a new Coulombic  
energy and force calculation approach (i.e. that of Wolf et al.) into  
Gromacs?

Harold Park