[gmx-users] Translational Pulling

[Ray Chao]

H
​i, Justin,

Actually I was using freeze groups together with pulling. However, the
atoms seemed to be frozen and weren't pulled away at all. Following is my
mdp file:

freezegrps               = X  Z
freezedim                = Y Y Y Y Y Y

pull                           =  umbrella
pull-geometry         =  distance
pull-dim                   =  N N Y
pull-ngroups            =  2
pull-group1-name   =  X
pull-group2-name   =  Z
pull-coord1-groups =  1   2
pull-coord1-rate       =  -0.01  ;velocity 0.01 nm/ps

I also tried to used constraints pulling, but it gave an error of "The pull
constraint reference distance for group 0 is <= 0".  What change do I need
to make to make the group X and Z approach each other?

Thank you very much
​