lammps/examples/gcmc/in.gcmc.lj

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# 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