Hi,

I am trying to characterize main thermodynamic properties of a high entropy alloy with a meam potential. I am mainly interested in the definition of the system pe, avg lattice constant and rdf @ 300 K, for different alloy compositions. I am running a simulation like this:

*units metal*

*boundary p p p*

*atom_style atomic*

*atom_modify map array*

*lattice fcc 3.68*

*region whole block 0 40 0 40 0 40*

*create_box 5 whole*

*lattice fcc 3.68 orient x 1 0 0 orient y 0 1 0 orient z 0 0 1*

*create_atoms 1 region whole*

*variable fMn equal 0.20*

*variable fNi equal (1-${fMn})/4*

*variable fCr equal (1-${fMn})/4*

*variable fFe equal (1-${fMn})/4*

*set type 1 type/fraction 2 $((v_fNi+v_fCr+v_fFe+v_fMn)) 5467*

*set type 2 type/fraction 3 $((v_fCr+v_fFe+v_fMn)/(v_fNi+v_fCr+v_fFe+v_fMn)) 6556*

*set type 3 type/fraction 4 $((v_fFe+v_fMn)/(v_fCr+v_fFe+v_fMn)) 7754*

*set type 4 type/fraction 5 $(v_fMn/(v_fFe+v_fMn)) 8574*

*pair_style meam/c*

*pair_coeff * * library.meam Co Ni Cr Fe Mn CoNiCrFeMn.meam Co Ni Cr Fe Mn*

*compute csym all centro/atom bcc*

*compute myRDF all rdf 500 1 1 2 2 cutoff 4.8*

*thermo 1000*

*thermo_style custom step pe lx ly lz press pxx pyy pzz*

*velocity all create 300.0 548494 rot yes dist gaussian*

*fix 1 all npt temp 300 300 0.1 iso 1 1 1*

*run 50000*

*minimize 1e-10 1e-10 10000 10000*

*unfix 1*

*reset_timestep 0*

*fix 4 all ave/time 100 1 100 c_myRDF[*] file my_rdf.txt mode vector*

*run 100*

*unfix 4*

*variable mype equal pe*

*variable real_ao equal “lx/40”*

*print ${mype} append PE.data*

*print ${real_ao} append lattice.data*

As far as I know, pe should stabilize around a certain value while pressure should stabilize around 0 (or 1 in my case), in order to consider a system relaxed. However, while my pe does stabilize, my pressure starts at about -1e5 bar at the first timestep and then fluctuates between -200 and 100 bar, it goes like this . Is it sufficient to consider the system stable or there is something wrong with the model? Thank you.

Cheers,

Stefano