[gmx-users] Warning: 1-4 interaction

[Moeed]

Hi everyone,

My attempt to conduct a NPT failed although everything seemed to be going
well. Topology is OK and I am just curious why system is blowing up all of a
sudden towards the end of simulation. I should mention that by changing
fourierspacing from 0.12 to 0.3 everything works fine till the end of run
and comparison between energy terms (up until the crash point) shows very
slight difference between two runs ( less than 2% even for electrostatic
terms). I am aware that blowing up is due to unphysical forces but is this
happening by accidient or there is an underlying reason I should take care
of.

Thanks,
Best,
Moeed

========================================
step 164300, remaining runtime:   241 s
step 164400, remaining runtime:   240 s
step 164500, remaining runtime:   240 s
step 164600, remaining runtime:   239 s
Warning: 1-4 interaction between 260 and 267 at distance 73679654.990 which
is larger than the 1-4 table size 2.250 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
=========================================
results till t=320 ps (before first run crash)
fourierspacing      =  0.12

LJ-14                       757.246    26.6239    26.5661 -0.0189929
-6.07777

Coulomb-14                 -186.509    15.9866    15.9529 -0.0112174
-3.5896

LJ (SR)                    -2691.84    117.026    107.231  -0.507373
-162.361

Coulomb (SR)                725.662    17.6483    17.5876  0.0158275
5.06483



fourierspacing      =  0.3


LJ-14                       757.129    26.4936    26.4578 -0.0149128
-4.77214

Coulomb-14                 -199.523     14.949     14.158 -0.0519427
-16.6218

LJ (SR)                     -2670.5    111.201    109.688    0.19784
63.3092

Coulomb (SR)                739.794    16.1807    15.4473  0.0521352
16.6834
====================================================
pbc              =  xyz


;        Run control
integrator          =  md
dt                  =  0.002
nsteps              =  1000000 ;5000
nstcomm             =  100

;        Output control
nstenergy           =  100
nstxout             =  100
nstvout             =  0
nstfout             =  0
nstlog              =  1000
nstxtcout          =  1000

;        Neighbor searching
nstlist             =  10
ns_type             =  grid

;        Electrostatics/VdW
coulombtype         =  PME
vdw-type            =  Shift
rcoulomb-switch     =  0
rvdw-switch         =  0.9 ;0

;        Cut-offs
rlist               =  1.25
rcoulomb            =  1.25 ;1.1
rvdw                =  1.0

;        PME parameters
fourierspacing      =  0.3
fourier_nx          =  0
fourier_ny          =  0
fourier_nz          =  0
pme_order          =  4
ewald_rtol         =  1e-5
optimize_fft      =  yes

;        Temperature coupling
Tcoupl              =  v-rescale
tc-grps             =  System  ;HEX
tau_t               =  0.1     ;0.1
ref_t               =  400     ;300

;        Pressure coupling
Pcoupl              =  Parrinello-Rahman
Pcoupltype          =  isotropic
tau_p               =  1      1           ;0.5
compressibility     =  4.5e-5 4.5e-5
ref_p               =  70    70

;        Velocity generation
gen_vel             =  yes
gen_temp            =  300.0
gen_seed            =  173529

;        Bonds
constraints             = all-bonds
constraint-algorithm = lincs
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