gcmc simple example

Hello lammps users, I am a new lammps learner and I wanna make clear about the fix gcmc command by perform a simple example, such as CH4 gas. So I tried myself to write the input script which may be uncompleted and have some errors. I appreciate it that if anyone can help me to modify the code. Cause’ it is urgent for me, I am awfully looking forword to your reply.

Thanks!

Best Regards,
Mengjia
Nanjing University, PRC.

The following is my input script :

#LAMMPS of ch4
units real
atom_style atomic
boundary s s s
timestep 0.5

create geometry

region box block 0.0 200.0 0.0 100.0 -250.0 250.0
create_box 1 box #1 types of atoms
mass 1 16.0425 # CH4
pair_style lj/sf 11.43 #cut-off=3*sigma-ch4
pair_coeff 1 1 0.2943 3.810

define groups

group ch4 type 1

fix 2 all gcmc 10 100 100 1 587623 298.0 -0.5 0.01

run 10000
thermo_style multi
thermo 100
write restart ch4

ERROR: Illegal simulation box (…/domain.cpp:356)