GCMC in LAMMPS giving an error "Lost Atoms"

Respected All,

I have written a script in Lammps, for GCMC. My system is adsorption of gas on Zeolite (taken from literature). After running the simulation, I am getting an error “Lost atoms”.

Here I am pasting the molecule input, LAMMPS input, data files, and the Output for your reference. It would be helpful to me if someone could suggest a way to clear the issue.

p.s: In the data file, I have included the coordinates of 6912 atoms that belong to the framework, while the remaining 4 atoms belong to the molecule.

LAMMPS version: September 2015 (colvars)

Thank you,

Yours sincerely,

Vardhan

Input:

Chabazite

units real
dimension 3
atom_style full
bond_style none
angle_style none
boundary p p p
pair_style lj/cut/coul/long 14.0 14.0 ## cut-off distance
pair_modify mix arithmetic shift no tail yes
kspace_style ewald 1.0e-6

read_data zeolite.data ## zeolite
region chabazite prism 0.0000 54.1169 0.0000 46.8666 0.0000 58.9931 -27.0584 0.0000 0.0000 side in units box
molecule h2smol h2s.txt

pair_coeff 1 1 0.0441 2.310 14.0 ## silicon

pair_coeff 2 2 0.1057 3.304 14.0 ## oxygen

pair_coeff 1 1 0.2424 3.600 14.0 ## S_h2s

pair_coeff 2 2 0.0994 2.500 14.0 ## H_h2s

pair_coeff 3 3 0.0000 0.000 14.0 ## S_com

mass 3 32.0650 ## S_h2s

mass 4 1.00794 ## H1_h2s

mass 5 1.e-20 ## S_com

group chabazite type 1 2
group h2s type 3 4 5

fix freeze chabazite setforce 0.0 0.0 0.0
velocity chabazite set 0.0 0.0 0.0 sum no
neighbor 2.0 bin
neigh_modify every 1 delay 10 check yes
velocity h2s create 298.0 9821144
timestep 1.0

fix h2s_rigidnvt h2s rigid/nvt/small molecule temp 298.0 298.0 1 mol h2smol

fix_modify h2s_rigidnvt dynamic/dof yes

fix h2s_gcmc h2s gcmc 1 100 100 0 9821144 298.0 1.0 20.0 mol h2smol pressure 0.986923 fugacity_coeff 0.992430 full_energy

variable sulfur atom “type==3”
variable hydrogen atom “type==4”
variable offsite atom “type==5”

group sulfur dynamic h2s var sulfur
group hydrogen dynamic h2s var hydrogen
group offsite dynamic h2s var offsite

variable nS equal count(sulfur)
variable nH equal count(hydrogen)
variable nX equal count(offsite)

variable tacc equal f_h2s_gcmc[2]/(f_h2s_gcmc[1]+0.1)
variable iacc equal f_h2s_gcmc[4]/(f_h2s_gcmc[3]+0.1)
variable dacc equal f_h2s_gcmc[6]/(f_h2s_gcmc[5]+0.1)
variable racc equal f_h2s_gcmc[8]/(f_h2s_gcmc[7]+0.1)

compute_modify thermo_temp dynamic/dof yes

thermo_modify lost ignore

thermo_style custom step temp press pe ke density atoms v_iacc v_dacc v_tacc v_racc v_nS v_nH v_nX

thermo 1

dump h2s_traj all xyz 2 dump.xyz

dump h2s_traj all image 2 dump.jpeg type type

dump_modify h2s_traj flush yes

run 20

molecule:

h2s molecule

4 atoms
3 bonds
3 angles

Coords

1 0.0000 0.0000 0.0000 ## S_h2s
2 0.9640 -0.9309 0.0000 ## H1_h2s
3 -0.9640 -0.9309 0.0000 ## H2_h2s
4 0.0000 -0.3000 0.0000 ## S_com

Types

1 1 ## S_h2s
2 2 ## H1_h2s
3 2 ## H2_h2s
4 3 ## S_com

Charges

1 0.00 ## S_h2s
2 0.21 ## H1_h2s
3 0.21 ## H2_h2s
4 -0.42 ## S_com

Bonds

1 1 1 2
2 1 1 3
3 2 1 4

Angles

1 1 2 1 3
2 2 2 1 4
3 2 4 1 3

Data file:

Chabazite

6916 atoms ## number of atoms
3 bonds
3 angles
0 dihedrals
0 impropers
5 atom types ## atom types, Si & O
2 bond types
2 angle types
0 dihedral types
0 improper types
0.0000 54.1169 xlo xhi
0.0000 46.8666 ylo yhi
0.0000 58.9931 zlo zhi
-27.0584 0.0000 0.0000 xy xz yz ## tilt factors for triclinic

Masses

1 28.0855 ## silicon
2 15.9990 ## oxygen
3 32.0650 ## S_h2s
4 1.00794 ## H1_h2s
5 1.e-20 ## S_com

Atoms

1 1 1 1.5 17.2009 42.9612 55.6093
2 1 1 1.5 21.8405 45.6394 55.6093
3 1 1 1.5 21.8401 40.2823 55.6093
.
.
.
.
.6911 1 2 -0.75 4.3759 0.2318 2.4581
6912 1 2 -0.75 -4.3338 10.3132 1.9160
6913 2 3 0.00 0.1000 0.1000 0.0000
6914 2 4 0.21 1.4400 0.1000 0.0000
6915 2 5 -0.42 0.3084 0.3158 0.0000
6916 2 4 0.21 0.0532 1.4392 0.0000

Pair Coeffs

1 0.0441 2.310 ## silicon
2 0.1057 3.304 ## oxygen
3 0.2424 3.600 ## S_h2s
4 0.0994 2.500 ## H_h2s
5 0.0000 0.000 ## S_com

Bonds

1 1 6913 6914
2 1 6913 6916
3 2 6913 6915

Angles

1 1 6914 6913 6916
2 2 6914 6913 6915
3 2 6915 6913 6916

Output
Ewald initialization …
G vector (1/distance) = 0.245045
estimated absolute RMS force accuracy = 0.000374866
estimated relative force accuracy = 1.1289e-06
KSpace vectors: actual max1d max3d = 6652 20 34460
kxmax kymax kzmax = 15 20 16
0 atoms in group FixGCMC:gcmc_exclusion_group:h2s_gcmc
0 atoms in group FixGCMC:rotation_gas_atoms:h2s_gcmc
WARNING: Neighbor exclusions used with KSpace solver may give inconsistent Coulombic energies (…/neighbor.cpp:441)
Neighbor list info …
1 neighbor list requests
update every 1 steps, delay 10 steps, check yes
master list distance cutoff = 16
ghost atom cutoff = 16
Memory usage per processor = 18.508 Mbytes
Step Temp Press PotEng KinEng Density Atoms iacc dacc tacc racc nS nH nX
0 0.015904701 3747097.1 906768.17 0.32773768 1.5367248 6916 0 0 0 0 1 2 1
ERROR: Lost atoms: original 7128 current 6912 (…/thermo.cpp:395)

THE END

two comments:

a) your LAMMPS version is very old. there have been quite a few
corrections and improvements to fix gcmc since. i strongly recommend
to upgrade LAMMPS to the latest version
b) you should equilibrate your "host" structure first without running
gcmc. you have a giant pressure and potential energy at step 0. that
is not a good sign and could be an indication of a problem with the
structure your data file, and not with fix gcmc.

axel.