error in gcmc result

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1

Dear Axel and users,

I am trying to run the GCMC simulation of a rigid and fixed mof structure to adsrob CO2 molecules. In simulation, the UFF/DREIDING inter-atomic parameters are used for MOF along with a three-site model parameter for CO2 (TraPPE). which pair coefficients carried data of UFF data. I just used the TraPPE parameters given in example/gcmc/CO2.txt.

I am using the lammps-23oct2017 version.

but in result file atom value not changing with respect to steps and other parameter changing but in gcmc atom no varry is very important.can any one suggest why it happening.when i changed it by pair style lj/cut instead of pair_style lj/cut/coul/long 12.500 ,it gave good result atom no got change.so,where is the problem in force-field parameter or any other place.

kindly suggest me about the problem how to figure out and valuable advice.
Thank you very much.

Regards,
satyaranjan

LAMMPS (23 Oct 2017)
Reading data file …
orthogonal box = (-17.1959 -17.1959 -17.1959) to (37.7508 37.7508 37.7508)
1 by 1 by 1 MPI processor grid
reading atoms …
675 atoms
Finding 1-2 1-3 1-4 neighbors …
special bond factors lj: 0 0 0
special bond factors coul: 0 0 0
0 = max # of 1-2 neighbors
0 = max # of 1-3 neighbors
0 = max # of 1-4 neighbors
1 = max # of special neighbors
Read molecule gas:
3 atoms with 6 types
0 bonds with 0 types
0 angles with 0 types
0 dihedrals with 0 types
0 impropers with 0 types
3 atoms in group gas
672 atoms in group sol
Ewald initialization …
WARNING: Using 12-bit tables for long-range coulomb (…/kspace.cpp:321)
G vector (1/distance) = 0.115288
estimated absolute RMS force accuracy = 0.437615
estimated relative force accuracy = 0.00131786
KSpace vectors: actual max1d max3d = 61 3 171
kxmax kymax kzmax = 3 3 3
WARNING: Fix gcmc using full_energy option (…/fix_gcmc.cpp:445)
0 atoms in group FixGCMC:gcmc_exclusion_group:2
0 atoms in group FixGCMC:rotation_gas_atoms:2
WARNING: Neighbor exclusions used with KSpace solver may give inconsistent Coulombic energies (…/neighbor.cpp:472)
Neighbor list info …
update every 1 steps, delay 10 steps, check yes
max neighbors/atom: 2000, page size: 100000
master list distance cutoff = 14.5
ghost atom cutoff = 14.5
binsize = 7.25, bins = 8 8 8
1 neighbor lists, perpetual/occasional/extra = 1 0 0
(1) pair lj/cut/coul/long, perpetual
attributes: half, newton on
pair build: half/multi/newton
stencil: half/multi/3d/newton
bin: standard
Setting up Verlet run …
Unit style : real
Current step : 0
Time step : 1
Per MPI rank memory allocation (min/avg/max) = 12.65 | 12.65 | 12.65 Mbytes
Step Atoms Volume Press TotEng Enthalpy Density
0 675 165892.04 2783183.7 1660098.4 8393636.5 0.09676333
10 675 165892.04 2783181.6 1660095.9 8393628.7 0.09676333
20 675 165892.04 2783179.9 1660093.8 8393622.7 0.09676333
30 675 165892.04 2783180 1660094 8393623.1 0.09676333

2

Dear Axel and users,
I am trying to run the GCMC simulation of a rigid and fixed mof structure
to adsrob CO2 molecules. In simulation, the UFF/DREIDING inter-atomic
parameters are used for MOF along with a three-site model parameter for
CO2 (TraPPE). which pair coefficients carried data of UFF data. I just
used the TraPPE parameters given in example/gcmc/CO2.txt. ​

I am using the lammps-23oct2017 version.

​

​there are several principal issues here.​
- your system is *tiny*. doing gcmc insertion moves are likely to cause
high energy differences and thus will be not very probable.
- your initial energy/pressure is *gigantic*. so either your initial
structure is bad or your force field parameters or both.
- it is rather pointless to try gcmc with a system that doesn't look like
it is properly relaxed.
- you are mix and matching force field parameters. that is a bad idea.
- it is not very relevant here, but there have been plenty of improvements
and fixes to the gcmc facility in LAMMPS, so you should upgrade your
version to the latest release.

​but in result file atom value not changing with respect to steps and other
parameter changing but in gcmc atom no varry is very important.can any one
suggest why it happening.when i changed it by pair style lj/cut
instead of pair_style
lj/cut/coul/long 12.500 ,it gave good result atom no got change.so,where is
the problem in force-field parameter or any other place.

kindly suggest me about the problem how to figure out and valuable advice.

​you need help and training from an experienced collaborator. the issues
​you are seeing are due to lack of proper understanding of the fundamentals
of managing MD simulations. a mailing list is not a classroom and thus you
cannot expect to get the support that you need only from this list. we may
help you with technical issues, and throw in the occasional advanced
technique suggestion, but we cannot teach you how to do your research as
such.

​axel.​