[gmx-users] LINCS waring during MD.

[Rajan Kumar]

Hi all,

I am trying to study wetting of water on Graphene oxide(GO). Energy
minimization for my
gives me following result which, I think is ok.
---------------------------------------------------------------------------------
Step= 5137, Dmax= 1.1e-06 nm, Epot= -9.40777e+03 Fmax= 4.76973e+01, atom=
2237
Step= 5138, Dmax= 1.3e-06 nm, Epot= -9.40776e+03 Fmax= 4.63983e+01, atom=
2237
Stepsize too small, or no change in energy.
Converged to machine precision,
but not to the requested precision Fmax < 20

Double precision normally gives you higher accuracy.

writing lowest energy coordinates.

Steepest Descents converged to machine precision in 5139 steps,
but did not reach the requested Fmax < 20.
Potential Energy  = -9.4077695e+03
Maximum force     =  4.7697334e+01 on atom 2237
Norm of force     =  3.9314783e+00
-------------------------------------------------------------------------------
Since, I don't have solvent in my system, just a water droplet, I proceeded
directly to mdrun, which gives me the usual LINCS warning after a few steps.
--------------------------------------------------------------------------------
Step 649931, time 649.931 (ps)  LINCS WARNING
relative constraint deviation after LINCS:
rms 0.000283, max 0.002029 (between atoms 3008 and 3010)
bonds that rotated more than 30 degrees:
 atom 1 atom 2  angle  previous, current, constraint length
  3008   3009   31.1    0.0949   0.0951      0.0950

-------------------------------------------------------
Program mdrun, VERSION 4.5.5
Source code file: constr.c, line: 189

Fatal error:
Too many LINCS warnings (1000)

-------------------------------------------------------

Same system with same mdp(http://goo.gl/Fx66sO) setting, I ran for 500 ps
does not give any error.
Please help me identify the problem.


-- 
Rajan Kumar
Indian Institute of Technology, Guwahati