[gmx-users] question about torsional potential fitting

Victor Rosas Garcia rosas.victor at gmail.com
Wed Oct 8 20:50:29 CEST 2014

Hello everybody,

I have calculated ab initio energies for a torsional potential that I
want to fit to a Fourier series. I have calculated the difference
between the ab initio energies and the forcefield with the torsion
potential set to zero (lets call that "diff curve").  This gives me a
somewhat jagged periodic function. I can then get a cosine series that
parallels the shape of the diff curve, but it is displaced along the
energy axis.
see this plot


If I shift the plot of the series, by adding a constant term, the fit
doesn't look so bad, to me at least, as in the following plot


However, I cannot add that constant term in the itp file for my
molecule. Is it enough if the energies calculated by the Fourier
series are parallel to the diff curve?

Best regards


More information about the gromacs.org_gmx-users mailing list