[gmx-users] Negative AFM forces??

[George Patargias DPhil]

Hello

I am sorry to bother everybody for this.

Thanks Berk for your previous answer about the AFM forces.
What is still not clear about the AFM pulling forces is
this: If the force exerted on the pulled group is indeed
F = k*(z_spring - z_pullgroup) then why do I get negative
forces? Does this mean that pulled group can overcome the
spring???

Thanks in advance.
George