[gmx-users] Energy conservation with water

[Michael Shirts]

I'd suggest compiling in double precision, and running with the following
parameters:

dt                                   = 0.002
nstlist                            = 10
rlist                                = 1.2
coulombtype               = PME
rcoulomb                     = 1.1
vdw-type                      = Switch
rvdw                              = 1.1
rvdw-switch                 = 1.05
tcoupl                            = No
pcoupl                          = No
constraints                   = all-bonds
constraint-algorithm   = shake
unconstrained-start    = no
Shake-SOR                 = no
shake-tol                      = 1e-12

This should give fairly good results for energy conservation.

You may possibly need to used improved Ewald parameters; I had
decent success with:

fourierspacing           = 0.10
pme_order                 = 6
ewald_rtol                  = 1e-06