[gmx-users] How the "Fmax" is determined without "emtol" in the mdp file?

[ZHANG Cheng]

Thank you so much, Justin and Mark!




------------------ Original ------------------
From:  "ZHANG Cheng"<272699575 at qq.com>;
Date:  Fri, Jan 18, 2019 09:55 PM
To:  "gromacs.org_gmx-users"<gromacs.org_gmx-users at maillist.sys.kth.se>;

Subject:  How the "Fmax" is determined without "emtol" in the mdp file?



I am doing an energy minimization in a vacuum condition. There is no "emtol" in the mdp file. The energy converges in the end, and tell me "Fmax < 10" as shown below. So how this "< 10" is determined?


Steepest Descents converged to Fmax < 10 in 4063 steps
Potential Energy  = -2.3973977e+04
Maximum force     =  9.8130465e+00 on atom 405
Norm of force     =  1.5696382e+00







My mdp file is:


integrator               = steep
nsteps                   = 10000 
nstxout                  = 0
nstfout                  = 0
nstlog                   = 100 


cutoff-scheme            = Verlet
nstlist                  = 20
ns_type                  = grid
pbc                      = xyz
verlet-buffer-tolerance  = 0.005


coulombtype              = reaction-field 
rcoulomb                 = 1.1
epsilon_r                = 15    ; 2.5 (with polarizable water)
epsilon_rf               = 0
vdw_type                 = cutoff  
vdw-modifier             = Potential-shift-verlet
rvdw                     = 1.1