Hi,all lammps user,
I am trying to use fix heat to do some jobs, but get some trouble. Below is my input file and question:
units metal
dimension 3
boundary p p p
atom_style full
read_data water-aurob.data #date file with water and gold nanorob, atom type of Au, H, O are 1, 2, 3, respectively.
group water type 2 3
group Au type 1
pair_style hybrid lj/cut/coul/cut 10.0 eam
bond_style harmonic
angle_style harmonic
#TIP3P water H=2, O=3, force field of water
pair_coeff 3 3 lj/cut/coul/cut 4.4276e-3 3.1880
pair_coeff 2 2 lj/cut/coul/cut 0.0000 0.0000
pair_coeff 2 3 lj/cut/coul/cut 0.0000 0.0000
bond_coeff 1 19.5343 0.9572
angle_coeff 1 2.3875 104.52
#interaction of water and au O=3, Au=1
pair_coeff 1 3 lj/cut/coul/cut 0.025592 3.6000
pair_coeff 1 2 lj/cut/coul/cut 0.0000 0.0000
#Au=1
pair_coeff 1 1 eam Au_u3.eam
neighbor 5.0 bin
neigh_modify every 5 delay 0 check yes
compute AuTemp Au temp #compute the temperature of Au
#output
thermo 100
thermo_style custom step temp pe ke vol press c_AuTemp
dump 1 all custom 1000 dump.water id x y z type
#Q1. in data file, each atom is noted with an ID, but in dump file, the atom’s ID is different with that in data file. Why the atom ID changes when dumping out?
What should I do to keep the atom ID same with that in data file?
timestep 0.002
#Equilibration
velocity all create 300.0 987652 dist gaussian
minimize 1.0e-4 1.0e-6 100 1000
fix 1 all npt temp 300 300 0.2 iso 1.0 1.0 0.1
run 5000
unfix 1
#Q2. After equilibrating, the temperature of Au is much lower than water. Below is tail of output.
step temp pe ke vol press c_AuTemp
4300 302.75023 -104088.16 9004.5097 2356077.1 -55.260318 117.49543
4400 303.2544 -104323.92 9019.505 2355043.5 -574.64413 117.47622
4500 303.7522 -103545.95 9034.3107 2352714 38.880211 117.13783
4600 302.64991 -104348.73 9001.5261 2352159.9 -168.85495 117.27725
4700 303.30205 -102656.08 9020.9222 2350598.7 166.41136 117.0715
4800 303.38856 -103859.01 9023.4952 2348929.5 -153.07481 116.188
4900 302.56047 -102998.83 8998.866 2347876.6 166.78818 114.59478
5000 302.39127 -104118.56 8993.8335 2347087.8 -84.769079 114.7133
5018 303.6491 -103782.3 9031.2445 2347267.9 -31.962956 115.53735
variable flux atom 40000*((2E-5)zz+(4E-12)*z+1.0445)
#this is a flux depend on the atom position.
thermo 10
fix 21 Au heat 1 v_flux
fix 22 all nve
run 50
unfix 21
thermo 100
run 50000
#Q3. When fix heat is called, AuTemp increase. After unfix, AuTemp decrease and temperature of water increase due to
heat transport from Au to water. However, temperature of water increase continuously though AuTemp is lower than it.
Finally, both temperature of water and Au become very high. Why this happen?
Any advice will be appreciated!