Hello,
Iam an amateur LAMMPS coder I wrote a code for the solidification of an alloy when i have run the code using the Tdump value equal to 1 in the fix command the temperature of the system in the thermo output statement is not reaching the desired temperature as described in the Fix but when i changed the Tdump value to 0.002 iam approximately reaching the desired temperature but the Manual says too small a Tdump value leads to fluctuations in the temperature and is not recommended.I would be glad if some one could say me how we exactly determine the Tdump value for a system and also suggest any changes required in the code .Iam sharing my code below and Thanks in advance.
---------- Initialize Simulation ---------------------
clear
units metal
dimension 3
boundary p p p
atom_style atomic
atom_modify map array
---------- Create Atoms ---------------------
lattice fcc 4
region box block 0 20 0 20 0 20 units lattice
create_box 4 box
lattice fcc 4 orient x 1 0 0 orient y 0 1 0 orient z 0 0 1
create_atoms 4 box
#replicate 20 20 20
set region box type/fraction 1 0.25 12541567
set region box type/fraction 2 0.25 12543796
set region box type/fraction 3 0.25 12541522
set region box type/fraction 4 0.25 12145
---------- Define Interatomic Potential ---------------------
pair_style eam/alloy
pair_coeff * * CoFeNiPd.set Co Fe Ni Pd
neighbor 2.0 bin
neigh_modify every 1 check yes
timestep 0.002 #from jafray 0.002 picometers
velocity all create 300 12345 mom yes rot no
---------- calculatingcentro symmetry to know whether the atom is distorted or not---------------------
compute csym all centro/atom fcc
compute peratom all pe/atom
compute pattern all cna/atom 3.414
thermo 100000
thermo_style custom step temp pe lx ly lz press pxx pyy pzz enthalpy
---------- Run Minimization ---------------------
#solidification of hea
dump 2 all custom 100000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 2 element Co Fe Ni Pd
fix 2 all npt temp 300 2300 1 iso 0 0 1
run 100000000
undump 2
unfix 2
dump 3 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 3 element Co Fe Ni Pd
fix 3 all npt temp 2300 2300 1 iso 0 0 1
run 5000000
undump 3
unfix 3
dump 4 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 4 element Co Fe Ni Pd
fix 4 all npt temp 2300 2200 1 iso 0 0 1
run 5000000
undump 4
unfix 4
dump 5 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 5 element Co Fe Ni Pd
fix 5 all npt temp 2200 2100 1 iso 0 0 1
run 5000000
undump 5
unfix 5
dump 6 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 6 element Co Fe Ni Pd
fix 6 all npt temp 2100 2000 1 iso 0 0 1
run 5000000
undump 6
unfix 6
dump 7 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 7 element Co Fe Ni Pd
fix 7 all npt temp 2000 1900 1 iso 0 0 1
run 5000000
undump 7
unfix 7
dump 8 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 8 element Co Fe Ni Pd
fix 8 all npt temp 1900 1800 1 iso 0 0 1
run 5000000
undump 8
unfix 8
dump 9 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 9 element Co Fe Ni Pd
fix 9 all npt temp 1800 1700 1 iso 0 0 1
run 5000000
undump 9
unfix 9
dump 10 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 10 element Co Fe Ni Pd
fix 10 all npt temp 1700 1600 1 iso 0 0 1
run 5000000
undump 10
unfix 10
dump 11 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 11 element Co Fe Ni Pd
fix 11 all npt temp 1600 1500 1 iso 0 0 1
run 5000000
undump 11
unfix 11
dump 12 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 12 element Co Fe Ni Pd
fix 12 all npt temp 1500 1400 1 iso 0 0 1
run 5000000
undump 12
unfix 12
dump 13 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 13 element Co Fe Ni Pd
fix 13 all npt temp 1400 1200 1 iso 0 0 1
run 5000000
undump 13
unfix 13
dump 14 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 14 element Co Fe Ni Pd
fix 14 all npt temp 1200 1100 1 iso 0 0 1
run 5000000
undump 14
unfix 14
dump 15 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 15 element Co Fe Ni Pd
fix 15 all npt temp 1100 1000 1 iso 0 0 1
run 5000000
undump 15
unfix 15
dump 16 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 16 element Co Fe Ni Pd
fix 16 all npt temp 1000 900 1 iso 0 0 1
run 5000000
undump 16
unfix 16
dump 17 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 17 element Co Fe Ni Pd
fix 17 all npt temp 900 800 1 iso 0 0 1
run 5000000
undump 17
unfix 17
dump 18 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 18 element Co Fe Ni Pd
fix 18 all npt temp 800 700 1 iso 0 0 1
run 5000000
undump 18
unfix 18
dump 19 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 19 element Co Fe Ni Pd
fix 19 all npt temp 700 600 1 iso 0 0 1
run 5000000
undump 19
unfix 19
dump 20 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 20 element Co Fe Ni Pd
fix 20 all npt temp 600 500 1 iso 0 0 1
run 5000000
undump 20
unfix 20
dump 21 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 21 element Co Fe Ni Pd
fix 21 all npt temp 500 400 1 iso 0 0 1
run 5000000
undump 21
unfix 21
dump 22 all custom 5000000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 22 element Co Fe Ni Pd
fix 22 all npt temp 400 300 1 iso 0 0 1
run 5000000
undump 22
unfix 22
dump 23 all custom 2500000 dump.td.* id type xs ys zs c_csym c_peratom c_pattern
dump_modify 23 element Co Fe Ni Pd
fix 23 all npt temp 300 300 1 iso 0 0 1
run 2500000
undump 23
unfix 23
write_data graph5.dat
write_restart graph5.rest
variable natoms equal “count(all)”
variable teng equal “c_peratom”
variable length equal “lx”
variable ecoh equal “v_tperatom/v_natoms”
#print “Total energy (eV) = {teng};"
print "Number of atoms = {natoms};”
print “Lattice constant (Angstoms) = {length};"
#print "Cohesive energy (eV) = {ecoh};”