[gmx-users] poly(lactic acid) .itp or .top file

[Chris O'Brien]

Hello all,

I am trying to develop an accurate topology file for poly(lactic acid). 
Most features of the topology file are obvious, but I have some questions 
about the dihedral parameters. How do I take quantum modeling (MP2 and DFT 
level) information about the barrier for rotating the dihedral angle and 
convert that into the parameters listed in the .itp file?

Same question for the improper dihedrals.  How important is the force 
constant value to successful modeling?  Can you just make it large to 
discourage (for example) a change of chirality?  If it is important to have 
these numbers accurately, does anybody know the best way to calculate them?

Thank you,

Chris O'Brien
Clemson University