From: Mayne, Christopher G (
Date: Thu Feb 06 2014 - 09:29:04 CST


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

Christopher Mayne

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


(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,