Hi lammps users,
I am running simulation about a simple 2D cooling progress. There are 600 solid wall atoms and 1000 fluid atoms. And the initial temperature for wall and fluid atoms is 100K and 300K respectively. Cooling progress for all liquid atoms, however, is not been observed. I will grateful for any review. my input file and part of results are shown as follows
Input file:
units metal
variable T_wall equal 100
variable T_fluid equal 300
variable spring_constant equal 32
dimension 2
boundary p f p
atom_style atomic
neighbor 1.0 bin
#-------------------------model----------------------------
lattice sq 4
#region box block 0 100 0 60 -0.25 0.25
region box block 0 100 0 20 -0.25 0.25
create_box 2 box
#-------------------------region----------------------------
region r_bot_wall block INF INF INF 2 INF INF
region r_top_wall block INF INF 17.0 INF INF INF
region r_flow block INF INF 2.01 16.99 INF INF
region r_flow_1 block INF INF 3.0 16.0 INF INF
#--------------------------create atoms----------------------
create_atoms 1 region box
delete_atoms region r_flow
group g_bot_wall region r_bot_wall
group g_top_wall region r_top_wall
group g_boundary union g_bot_wall g_top_wall
create_atoms 2 random 1000 987654 r_flow_1
group g_flow type 2
mass 1 107.86820
mass 2 39.948
#-----------------------------LJ potential------------------
pair_style lj/cut 10.0
pair_coeff 1 1 0.408 2.551 10.0
pair_coeff 2 2 0.0104 3.405 10.0
pair_coeff 1 2 0.0652 2.978 10.0
#------------------------initialization velocity------------
velocity g_boundary create ${T_wall} 987654 dist gaussian
velocity g_flow create ${T_fluid} 982454 dist gaussian
#-------------------------spring model for wall atoms----------------------------------------------
fix spring_boundary_wall g_boundary spring/self ${spring_constant}
#-------------------------energy minimization-------------------------------------
minimize 1.0e-6 1.0e-9 10000 20000
min_style cg
neigh_modify delay 1 check yes
#-------------------------thermostat for boundary---------------------------------
compute th_com_wall g_boundary temp
fix th_fix_wall g_boundary langevin {T_wall} {T_wall} 0.1 699483
fix_modify th_fix_wall temp th_com_wall
#-------------------------thermostat for liquid------------------------------------
compute th_com_flow g_flow temp
fix th_scale_flow g_flow langevin {T_fluid} {T_fluid} 0.1 699483
fix_modify th_scale_flow temp th_com_flow
fix 1 g_flow nve
fix 2D all enforce2d
fix spring_recenter_1 g_boundary recenter INIT INIT INIT
#------------------------------------equilibrium---------------------------------------
thermo 50000
thermo_style custom step temp pe etotal press c_th_com_wall
thermo_modify temp th_com_flow
dump 1 all atom 50000 dump.flow.lammpstrj
timestep 0.001 #1fs
run 1000000
#------------------------------------------cooling---------------------------------------
unfix th_scale_flow
timestep 0.001 #1fs
run 100000000
Part of output results:
step temp (fluid) pe etotal press temp (wall)
10000000 301.88594 -147.80967 -121.82114 -14210.851 100
10050000 303.80657 -147.98811 -121.83424 -14080.876 100
10100000 301.56028 -147.78287 -121.82237 -14289.941 100
10150000 297.73027 -147.46366 -121.83287 -13792.612 100
10200000 304.71753 -148.06772 -121.83542 -14123.021 100
10250000 295.72202 -147.28893 -121.83103 -13916.466 100
10300000 294.06483 -147.14892 -121.83368 -14105.636 100
10350000 303.14187 -147.92636 -121.82971 -13939.447 100
10400000 290.92003 -146.87705 -121.83254 -14121.636 100
10450000 299.05886 -147.58886 -121.84371 -13908.394 100
10500000 307.24879 -148.27989 -121.82968 -14583.084 100
10550000 302.25204 -147.85106 -121.83101 -14051.313 100
10600000 302.15235 -147.84872 -121.83725 -14198.357 100
10650000 291.76508 -146.95118 -121.83392 -14024.474 100
10700000 306.11183 -148.19077 -121.83844 -14131.939 100
10750000 286.24672 -146.47101 -121.82882 -14062.151 100
10800000 307.61966 -148.3187 -121.83657 -14228.103 100
10850000 303.42176 -147.95852 -121.83778 -13896.82 100
Best wishes,
Qiangqiang Sun