[gmx-users] Umbrella Sampling: At diff force constant

[Md Masrul Huda]

Dear All:

I am doing umbrella sampling for a dimer (Consist of two molecules
 stacking  together, no physical bond). I tried different force constants,
I got different PMF for each of them. Could you suggest me, How reliably
can I choose force constant.  Followings are the settings:

; Pull code
pull                    = yes
pull_ncoords            = 1
pull_ngroups            = 2
pull_group1_name        = FXD
pull_group2_name        = PUL
pull_coord1_type        = umbrella
pull_coord1_geometry    = distance
pull_coord1_dim         = N N Y
pull_coord1_groups      = 1 2
pull_coord1_start       = yes
pull_coord1_rate        = 0.0
pull_coord1_k           = 1000/500/200

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 Thanks in advance for your valuable suggestions.

Sincerely yours,
Masrul