Hello Everyone,
I am using LAMMPS 22 Aug 2018 stable version. I am attempting these SGC simulations on an HPC cluster (I use multiple nodes). The interatomic potentials I am using for this purpose are 2NN MEAM. The issue is - the concentration of impurity atoms § in the bulk (Fe) doesn’t seem to converge (with fix atoms/swap ‘semigrand’ set to ‘yes’). I already know the equilibrium P concentration in bulk Fe. But I am trying to see the same through these simulations. All I am trying for is to obtain the equilibrium impurity concentration and configuration in the bulk Fe at different temperatures with atoms swapping probability as a function of difference in chemical potentials of Fe and P.
If my inputs are not logical, there is no way I can get results. So I keep looking for possible mistakes from me. So far I have tried quite a few things. Few are - 1. Increased the system size to see the change in concentration (that I am expecting), 2. credibility of the 2NN MEAM potential that I am using for these simulations (I am using the 2NN MEAM potential with which some other group has obtained the results using a different MD code), 3. run the simulations for 1ns.
Sorry for the inconvenience but it would be very helpful if someone could give any suggestions. Here is the input script:
variable T equal 1300
units metal
dimension 3
boundary p p p
atom_style atomic
read_data Fe-P_bulk.lmp
pair_style meam/c
pair_coeff * * library.meam Fe P FeP.meam Fe P
fix 1 all box/relax iso 0.0001 nreset 10
thermo 10
thermo_style custom step temp pxx pyy pzz press pe etotal lx ly lz
minimize 1.0e-12 1.0e-12 100000 100000
unfix 1
velocity all create $T 825577 mom yes rot no
reset_timestep 0
fix 2 all npt temp $T $T 0.1 iso 0.0 0.0 0.1
run 100000
unfix 2
fix 3 all nvt temp $T $T 0.1
run 100000
unfix 3
dump 2 all custom 10 dump.semiGC id type xu yu zu
dump_modify 2 append yes
reset_timestep 0
timestep 0.001
fix 4 all atom/swap 1 500 12345 $T semi-grand yes types 1 2 mu 1.9 1.0
fix 5 all nvt temp $T $T 0.1
run 1000000
Thanks and regards
Praveen
LTH
Lund, Sweden