Temperature fall to zero in gcmc

Dear lammps-users,

I used gcmc+nvt to simulate the methane (group methane) adsorption in clay slit using command, the clay (group illite) was kept rigid.

#keep illite slit rigid
neigh_modify delay 0 every 1 check yes exclude group illite illite
fix fixillite illite setforce 0.0 0.0 0.0
#initial minimize
minimize 1.0e-4 1.0e-6 100 1000
reset_timestep 0

methane md+gcmc

compute Tch4 methane temp
compute_modify Tch4 dynamic/dof yes
fix {pressure}methanenvt methane nvt temp {temp} {temp} 100.0 fix_modify {pressure}methanenvt dynamic/dof yes temp Tch4

fix sorption methane gcmc {Nfreq} {Nexchange} {Nmove} 12 9999999 {temp} {mu} {disp} pressure {pressatom} & fugacity_coeff {fugacity_coeff} charge 0 group methane grouptype 12 methane tfac_insert 2

I got a unreasonable result, the temperature fall to zero and the potential energy becomes very high when the number of methane in system was zero, even some other methane were inserted in system. And when I run pure gcmc without nvt MD, everything seems right, temperature and potential energy all fluctuate in normal range.

The output of GCMC+MD was attached. Anyone has suggestions? How to perform a right simulation of GCMC+MD?

Best regard.

Dongbo Wang

1.out (45 KB)

Aidan (CCd) can likely answer this Q.


Thanks for your reply. I’m looking forward to Aidan’s answer.