The model consists of the SiC particle and Cu matrix. Fix npt is used to relax the model at first.
velocity all create ${T} 8819988 mom yes rot yes dist gaussian
fix relax all npt temp ${T} ${T} 0.1 iso 0.0 0.0 1.0 (T=1000K, units:metal, boundary: PPP)
The temperature of the Cu matrix and the SiC particle is computed.
The same thing happened when fix nvt is used to relax all(group).
When fix nvt is used to the SiC group and Al group, temperature of them is 1000K and that of all group is 1000K. Is it right?
fix relax_cu cu nvt temp ${T} ${T} 0.1
fix_modify relax_cu temp cutemp
fix relax_sic sic nvt temp ${T} ${T} 0.1
fix_modify relax_sic temp sictemp
austlammps:
Is it right?
Yes and no. Due to choosing two independent thermostat you have enforced equipartitioning between the two groups. But if you want to understand whether your system is properly equilibrated and whether there are intrinsic issues with your setup that will cause one group to accumulate kinetic energy versus the other, then not.
For starters, you should not look at individual temperature values (e.g. at the end of a run) but the trends and especially from the very beginning. Are the values converging toward the desired equipartitioning or not, perhaps only slowly. Also, you may want to use a dissipative thermostat instead of fix nvt (e.g. fix nve + fix langevin) at the beginning of the equilibration to speed up the equipartitioning process.
#***************1initialization***************
units metal
dimension 3
boundary p p p
atom_style atomic
timestep 0.001
neighbor 2.0 bin
neigh_modify every 1 delay 10 check yes
#***************parameters***************
variable prerelax_step equal 100000
#***************modelling and setting***************
variable latconst_a equal 4.150 #1000K lattice constant
variable latconst_s equal 4.389 #1000K lattice constant
variable Al_x equal 27
variable Al_y equal 54
variable Al_z equal 27
variable sic_y equal ${Al_y}*${latconst_a}/2/${latconst_s}
##nano SiC 半径，直径12variable SiC_r equal 12 #12*4.389=52.668
#create cu
lattice fcc ${latconst_a} origin 0.25 0.25 0.25
region aluminum block -${Al_x} ${Al_x} 0 ${Al_y} -${Al_z} ${Al_z}
create_box 3 aluminum
create_atoms 3 region aluminum
#sic
lattice custom ${latconst_s} a1 1.0 0.0 0.0 a2 0.0 1.0 0.0 a3 0.0 0.0 1.0 &
basis 0.0 0.0 0.0 &
basis 0.5 0.5 0.0 &
basis 0.0 0.5 0.5 &
basis 0.5 0.0 0.5 &
basis 0.25 0.25 0.25 &
basis 0.25 0.75 0.75 &
basis 0.75 0.25 0.75 &
basis 0.75 0.75 0.25
region sic_del sphere 0 ${sic_y} 0 ${SiC_r}
delete_atoms region sic_del
create_atoms 2 region sic_del &
basis 1 1 &
basis 2 1 &
basis 3 1 &
basis 4 1 &
basis 5 2 &
basis 6 2 &
basis 7 2 &
basis 8 2
mass 1 28.085 #Si
mass 2 12.011 #C
mass 3 26.982 #Al
write_data model.data
#**************************group sic al
group sic region sic_del
group al subtract all sic
info group
#***************************************************interatomic potential********
pair_style hybrid eam/fs tersoff morse 10 morse 10
pair_coeff * * eam/fs Al_mm.eam.fs NULL NULL Al
pair_coeff * * tersoff SiC_1989.tersoff Si C NULL
pair_coeff 1 3 morse 1 0.4824 1.322 2.920 #Al-Si
pair_coeff 2 3 morse 2 0.4691 1.738 2.246 #Al-C
#***************************************************minimize********
min_style cg
minimize 1e-18 1e-18 10000 10000
#**************************************************variable**************************
variable T equal 1000
shell mkdir t_${T} ./t_${T}/relax_${T}
variable path_relax string ./t_${T}/relax_${T}/
#***************equilibration***********************relax_{T}*********
reset_timestep 0
timestep 0.001
compute altemp al temp
compute sictemp sic temp
thermo 100
thermo_style custom step temp c_altemp c_sictemp pe pxx pyy pzz ke
dump relax all custom 10000 ${path_relax}relax_nanoSiCAl${T}.equil.*.lammpstrj id type x y z
velocity all create ${T} 8819988 mom yes rot yes dist gaussian
#fix relax all npt temp ${T} ${T} 0.1 iso 0.0 0.0 1.0
fix relax_al al nvt temp ${T} ${T} 0.1
fix_modify relax_al temp altemp
fix relax_sic sic nvt temp ${T} ${T} 0.1
fix_modify relax_sic temp sictemp
#fix_modify relax temp altemp
run ${prerelax_step}
undump relax
unfix relax_al
unfix relax_sic
units metal
atom_style atomic
atom_modify map array
boundary p p p
atom_modify sort 0 0.0
# temperature
variable t equal 1800.0
# cubic diamond unit cell
variable a equal 5.431
lattice custom $a &
a1 1.0 0.0 0.0 &
a2 0.0 1.0 0.0 &
a3 0.0 0.0 1.0 &
basis 0.0 0.0 0.0 &
basis 0.0 0.5 0.5 &
basis 0.5 0.0 0.5 &
basis 0.5 0.5 0.0 &
basis 0.25 0.25 0.25 &
basis 0.25 0.75 0.75 &
basis 0.75 0.25 0.75 &
basis 0.75 0.75 0.25
region myreg block 0 4 &
0 4 &
0 4
create_box 8 myreg
create_atoms 1 region myreg &
basis 1 1 &
basis 2 2 &
basis 3 3 &
basis 4 4 &
basis 5 5 &
basis 6 6 &
basis 7 7 &
basis 8 8
mass * 28.06
velocity all create $t 5287287 loop geom
# Equilibrate using Stillinger-Weber model for silicon
pair_style sw
pair_coeff * * Si.sw Si Si Si Si Si Si Si Si
thermo_style custom step temp epair etotal econserve press
thermo 10
fix 1 all nvt temp $t $t 0.1
timestep 1.0e-3
neighbor 1.0 bin
neigh_modify every 1 delay 10 check yes
run 100
write_restart restart.equil
clear
read_restart restart.equil
pair_style sw threebody on
pair_coeff * * mWxL.sw mW mW mW mW xL xL xL xL
thermo_style custom step temp epair etotal econserve press
thermo 10
fix 1 all nvt temp $t $t 0.1
timestep 1.0e-3
neighbor 1.0 bin
neigh_modify every 1 delay 10 check yes
run 100
clear
read_restart restart.equil
pair_style hybrid sw threebody on sw threebody off
pair_coeff * * sw 1 mWxL.sw mW mW mW mW NULL NULL NULL NULL
pair_coeff * 5*8 sw 2 mWxL.sw mW mW mW mW xL xL xL xL
info coeffs
thermo_style custom step temp epair etotal econserve press
thermo 10
fix 1 all nvt temp $t $t 0.1
timestep 1.0e-3
neighbor 1.0 bin
neigh_modify every 1 delay 10 check yes
run 100