From: ehsan zahedinejad (
Date: Sat Jan 19 2013 - 19:12:06 CST

Dear VMD users,

In the charge optimization step of fftk, three factors including "dipole
moment", "water interaction energy and distance" are the target data. The
new fftk version writes out the dipole ratio of QM to MM but not energy and
distance. How can we be informed about these targets in optimization to be
sure they are fulfilled by optimization procedure?

The second important matter is the ratio of dipole moments. In the tcl file
of charge optimization a ratio between 1.2-1.5 is considered as an
acceptable target. But CHARMM general force field tutorial says dipole
moment of MM force field should be 30% higher than QM level (MP2). Is that
still OK to have dipole moment 20-50% higher than MM dipole moment? For
example what if my ratio is 1.4?

And thanks for this amazing tool,