From: Daniel Klose (
Date: Fri Jul 26 2013 - 01:29:14 CDT

Dear FFTK developers,

thank you for the program, it's a great help!

I've only got two brief questions:
1) In the resulting potential energy plot from the dihedral optimization, I observed that for some frames the final energy including the dihedrals has a LOWER energy than the initial MM energy without the dihedrals. The QM energy may be even lower.
I thought from the equations that the dihedral energy can only be positive, so how can the final energy be lower?

Since this is only the case for some frames, is that an indication that something went wrong for those few frames? The molecules looked normal though and there was no error in the QM calculation of the dihedral potential surface.

2) Is the newer paper on FFTK you mentioned in previous emails already available by any chance?

Thanks for your advice on the dihedrals!

With best wishes,