Dear all, Does anyone know if it possible to somehow do umbrella sampling in angles (rather than distances) using the pull code? The stuff I turn up in the manual all only seems to involve distances.
Alternatively, is there any way to make angle restraints use only simple harmonic springs rather than the cosine function that is typically used? My current problem is that I need to compute the PMF for rotating a small molecule through a particular angle. Using the angle_restraints cosine functional form gives me two zeros of the force when I only want one. If the energy landscape were smooth, this would be no problem, because one of the zeros is an unstable fixed point (the potential energy is high) and only the other is stable. But since the energy landscape is pretty rough, my molecule can actually get trapped at the unstable zero when it happens to coincide with a minimum in the energy landscape. This would obviously be solved by using simple harmonic restraints (as done with distance and dihedral restraints, but not with angle restraints, strangely enough). Is there a work-around? Or do I have to implement the harmonic form myself? Thanks, David _______________________________________________ gmx-users mailing list gmx-users@gromacs.org http://www.gromacs.org/mailman/listinfo/gmx-users Please don't post (un)subscribe requests to the list. Use the www interface or send it to [EMAIL PROTECTED] Can't post? Read http://www.gromacs.org/mailing_lists/users.php
