Help: energy minimization does not work


I tried to run DNA simulations from the initial configurations from a pdb file. It seems that the 3spn model is comfortable with some configurations that produce too large force.

So it prints out following message( I do not know whether to consider it as a error message or not)

Large force i=68, j=142,itag=60, jtag=110,r=3.745416
forecoul=0.000000, forcelj=1705.857988

Apparently, it complains that some force is huge. To solve this problem, I use energy minimization. Theoretically, it should work, but it does not work in my case. I use the default minimization style, and no matter how strictly I impose the minimization condition, it does not work.

In addition to that, I try to manually change the coordinates of the pair that produces large force, it does not work. (itag and jtag represents the atom ids that leading to this problem.)

Have anyone ever experienced this kind of situation?

Thank you

Are you sure you have specified the LJ potential parameters correctly
(i.e. right units)?