[gmx-users] pulling with constant force

[Ming Tang]

Dear list,

I want to pull my protein away from each other using a constant force. I fix one end (group 'start') and used the following pull code but found that 2 pulling groups are getting closer no matter whether I set pull-coord1-k  as 1000 or -1000.


; COM pulling.
pull                = constant-force
pull-geometry       = direction-periodic
pull-start          = yes
pull-ngroups        = 2
pull-ncoords        = 1
pull-coord1-groups  = 1 2
pull-group1-name    = start
pull-group2-name    = end
pull-coord1-k       = 1000
pull-coord1-vec     = 1 0 0

is my code correct? Do I have to set a virtual point to pull the 'end' group?

Your help will be appreciated!