From: Mayne, Christopher G (cmayne2_at_illinois.edu)
Date: Thu Feb 06 2014 - 11:51:34 CST

Shane,

Thanks for the files. I was able to reproduce your error. The problem originates from the fact that your molecule is comprised of three residues that contain atoms with overlapping atom names. Although the atoms with the same name are in different residues (in accordance with NAMD/psf requirements), this seems to choke ffTK. While I've found the origin of your error, I haven't yet disentangled several other places where this will likely cause problems.

I'll add this onto the list of things to work on (it's kind of a long list), but my suggestion is for you to redefine your PSF making the molecule a single residue containing uniquely named atoms.

Regards,
Christopher Mayne

On Feb 6, 2014, at 9:29 AM, Christopher Mayne wrote:

Shane,

Without the PSF and PDB files you're using, I cannot make much of a guess. Can you send them?

Regards,
Christopher Mayne

On Feb 6, 2014, at 8:10 AM, Shane.OMahony wrote:

Hi,

(Using VMD version 1.9.2a35)
I'm trying to use the fftk to calculate the charges on a molecule. When I click "Calculate from PSF" in the Charge constraints section of Opt. Charges, I get the following error:

can't use non-numeric string as operand of "+"
can't use non-numeric string as operand of "+"
    while executing
"expr { $psfAtomCharge + [$temp get charge] } "
    (procedure "::ForceFieldToolKit::gui::coptCalcChargeSumNEW" line 44)
    invoked from within
"::ForceFieldToolKit::gui::coptCalcChargeSumNEW $molID"
    invoked from within
".fftk_gui.hlf.nb.chargeopt.cconstr.calcFromTOP invoke "
    invoked from within
".fftk_gui.hlf.nb.chargeopt.cconstr.calcFromTOP instate {pressed !disabled} { .fftk_gui.hlf.nb.chargeopt.cconstr.calcFromTOP state !pressed; .fftk_gui...."
    (command bound to event)

I have not come across the error when using the FFTK to parameterize smaller molecules. Do you have any idea of what's causing this?

Thanks for the help,
Shane