[gmx-users] warning 1-4 interaction in QMMM simulation

[andrian]

Dear gromacs users

i was trying to perform micro-iterative QMMM optimization using 
gromacs/orca interface... in mdp file, i set bOpt = yes, then i got a 
warning like this:

"Warning: 1-4 interaction between 3 and 6 at distance 3.565 which is 
larger than the 1-4 table size 2.000 nm, These are ignored for the rest 
of the simulation, This usually means your system is exploding, if not, 
you should increase table-extension in your mdp file, or with user 
tables increase the table size"

note: my sistem has been successfully minimized and also NVT restrained 
simulation...


anyone can help ? thank you so much..

cheers

***************************************
title                    = my_mdp_file
cpp                      = /lib/cpp
include                  =
define                   =

integrator               = steep

tinit                    = 0
dt                       = 0.01
nsteps                   = 100

nstcomm                  = 1
comm_grps                = system

emtol                    = 100.0
emstep                   = 0.001

nstxout                  = 1
nstvout                  = 1
nstfout                  = 1
nstlog                   = 1
nstenergy                = 1
nstxtcout                = 1
xtc-precision            = 1000
xtc_grps                 = system
energy_grps              = QMatoms MMatoms

nstlist                  = 1
ns_type                  = grid
pbc                      = xyz
rlist                    = 1.0
coulombtype              = PME
rcoulomb-switch          = 0
rcoulomb                 = 1.0
epsilon_r                = 1.0
fourierspacing          = 0.12
ewald_rtol         = 1e-5

vdwtype                  = Cut-off
rvdw                     = 1.0
DispCorr                 = No

QMMM                     = yes
QMMM-grps                = QMatoms
QMmethod                 = RHF
QMbasis                  = STO-3G
QMMMscheme               = normal
QMcharge                 = 1
QMmult                   = 1
bOPT                     = yes
bTS                      = no

constraints              = none

<ORCAINFO file>
! AM1 PModel

%scf
   SCFMode Direct
   MaxIter 1500
   UseCheapInts true
end

qmmm.inp file produced by gromacs

#input-file generated by gromacs
!QMMMOpt TightSCF
! AM1 PModel


%scf
   SCFMode Direct
   MaxIter 1500
   UseCheapInts true
end
%geom
    Constraints
         {C 0 C}
         {C 8 C}
      end
    end
*xyz  1 1
   6 109.5018196  61.3748932  61.6309643
   1  2.3429996   2.3269998   2.5830004
   1  2.2759999   2.4849999   2.5680000
   6  2.4526897   2.4437210   2.4452071
   1  2.5284982   2.3686990   2.4200514
   8  2.5167450   2.5439975   2.5247785
   1  2.4429335   2.4939966   2.3479901
   1  2.4590001   2.5799999   2.5840002
   1 12.1445608  12.8626895  13.1234348
   8  2.7731431   2.5095880   2.3919705
   1  2.8239998   2.5810000   2.4270001
   1  2.6960000   2.5050002   2.4649999
   1  2.7079999   2.5490001   2.3260000
*

-- 
Andrian Saputra
Department of Pharmaceutical Science
Sumatera Institute of Technology, Indonesia