[gmx-users] umberlla sampling

[Ali Mohyeddin]

Dear Justin,

In the tutorial of "umbrella sampling
<http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin/gmx-tutorials/umbrella/index.html>",
what happens if we set the pull_coord1_rate to zero value? Does it work
like a harmonic force (spring) between two groups with a constant distance
averagely?  Indeed, I need to fix the distance between two groups and then
start to pull them.

;Pull code
pull                    = yes
pull_ngroups            = 2
pull_ncoords            = 1
pull_group1_name        = Chain_B
pull_group2_name        = Chain_A
pull_coord1_type        = umbrella      ; harmonic biasing force
pull_coord1_geometry    = distance      ; simple distance increase
pull_coord1_groups	= 1 2
pull_coord1_dim         = N N Ypull_coord1_rate        = 0
; 0 nm per ps = 10 nm per ns
pull_coord1_k           = 1000          ; kJ mol^-1 nm^-2
pull_coor1_start        = yes           ; define initial COM distance >0

Best regards,

Ali Mohyeddin