lammps/examples/gcmc/in.gcmc.lj

# GCMC for LJ simple fluid, no dynamics
# T = 2.0
# rho ~ 0.5
# p ~ 1.5
# mu_ex ~ 0.0
# comparable to Frenkel and Smit GCMC Case Study, Figure 5.8 

# variables modifiable using -var command line switch

variable        mu index -1.25
variable        temp index 2.0
variable	disp index 1.0
variable        lbox index 5.0

# global model settings

units           lj
atom_style      atomic
pair_style      lj/cut 3.0 
pair_modify	tail no # turn of to avoid triggering full_energy

# box

region		box block 0 ${lbox} 0 ${lbox} 0 ${lbox}
create_box	1 box

# lj parameters

pair_coeff	* * 1.0 1.0
mass		* 1.0

# we recommend setting up a dedicated group for gcmc

group		gcmcgroup type 1

# gcmc

fix             mygcmc gcmcgroup gcmc 1 100 100 1 29494 ${temp} ${mu} ${disp}

# atom count

variable 	type1 atom "type==1"
group 		type1 dynamic gcmcgroup var type1
variable        n1 equal count(type1)

# averaging

variable	rho equal density
variable	p equal press
variable	nugget equal 1.0e-8
variable        lambda equal 1.0
variable     	muex equal ${mu}-${temp}*ln(density*${lambda}+${nugget})
fix 		ave all ave/time 10 100 1000 v_rho v_p v_muex v_n1 ave one file rho_vs_p.dat
variable	rhoav equal f_ave[1]
variable	pav equal f_ave[2]
variable	muexav equal f_ave[3]
variable	n1av equal f_ave[4]

# output

variable	tacc equal f_mygcmc[2]/(f_mygcmc[1]+${nugget})
variable	iacc equal f_mygcmc[4]/(f_mygcmc[3]+${nugget})
variable	dacc equal f_mygcmc[6]/(f_mygcmc[5]+${nugget})
compute_modify  thermo_temp dynamic yes
thermo_style    custom step temp press pe ke density atoms v_iacc v_dacc v_tacc v_rhoav v_pav v_muexav v_n1av
thermo          1000

# run

run             10000