amber torsion energy

Letif Mones letif... at
Mon Apr 22 15:23:20 UTC 2013


I did a molecular mechanical calculation in cp2k using an amber topology file (force field: amber99). When I checked the bonded energy terms I found that the bond and angle terms are correct but the dihedral energy is twice as the energy calculated by sander. I think the reason is that in the amber FF the form of the torsion potential is: K / 2 * [ 1 + cos[ M*PHI - PHI0 ] ] while cp2k uses the form of  K * [ 1 + cos[ M*PHI - PHI0 ] ].
So should not the torsion force constant read from an amber topology file be multiplied by 0.5 (and the improper one too as it has the same form)?


More information about the CP2K-user mailing list