amber torsion energy

Letif Mones letif... at gmail.com
Mon Apr 22 17:23:20 CEST 2013


Hi,

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)?

Letif





More information about the CP2K-user mailing list