[gmx-users] (no subject)

[ARGYRIOS KARATRANTOS]

I have a polymer chain grafted on a surface and do energy minimization (steepest
descent) . when I take no interaction between surface and chain everything
works fine. When I use van der wall interaction between surface and the chain
after the energy minimization I get

Potential energy = nan 

What does this mean? can I continue an mdrun after having this message or
something goes wrong
Argyris Karatrantos