[Pw_forum] constraints: planar and torsion angles

[Norbert Nemec]

Hi there,

in case someone is curious about the commits I just checked in. Apart from some cleanup and some better logging output, I changed the internal handling of angle constraints:

Planar and and torsion angles used to be handled internally by their cosine. This had caused a problem for angles of 0 or 180 degree, where the derivative of the constraint would become zero and the constraint could not be enforced correctly. Specifically, this caused problems for planar benzene molecules that I tried to constrain.

With my change, the constraints are now internally handled as angle, the torsion angle as signed angle. It works beautifully for my test case. I adjusted the metadynamics code, otherwise, no code seems to be affected.

For the user, there should be no difference except in the case that someone would have explicitly specified torsion angles with incorrect sign in the input file. I doubt that anyone would do that...

Greetings,
Norbert
-- 
GMX DSL: Internet-, Telefon- und Handy-Flat ab 19,99 EUR/mtl.  
Bis zu 150 EUR Startguthaben inklusive! http://portal.gmx.net/de/go/dsl