Uniaxial Compression Simulation
This is a LAMMPS input to study deformation mechanisms during uniaxial compression process of an aluminum single crystal oriented in the <100> direction. Technically, this example uses a parallel molecular dynamics code, LAMMPS (Large Scale Atomic/Molecular Massively Parallel Simulator).
# Input file for uniaxial compressive loading of single crystal aluminum # Mark Tschopp, November 2010 # Initalization units metal dimension 3 boundary p p p atom_style atomic variable latparam equal 4.05 lattice fcc ${latparam} region whole block 0 10 0 10 0 10 create_box 1 whole region upper block INF INF INF INF INF INF units box lattice fcc ${latparam} orient x 1 0 0 orient y 0 1 0 orient z 0 0 1 create_atoms 1 region upper # Force-field (interatomic potential) defination pair_style eam/alloy pair_coeff * * Al99.eam.alloy Al # Equilibration process settings compute csym all centro/atom fcc compute peratom all pe/atom reset_timestep 0 timestep 0.001 velocity all create 300 12345 mom yes rot no fix 1 all npt temp 300 300 1 iso 0 0 1 drag 1 thermo 1000 thermo_style custom step lx ly lz press pxx pyy pzz pe temp run 20000 # Deformation process settings unfix 1 variable tmp equal "lx" variable L0 equal ${tmp} print "Initial Length, L0: ${L0}" reset_timestep 0 fix 1 all npt temp 300 300 1 y 0 0 1 z 0 0 1 drag 1 variable srate equal 1.0e10 variable srate1 equal "-v_srate / 1.0e12" fix 2 all deform 1 x erate ${srate1} units box remap x # Output strain and stress info to file for units metal, pressure is in [bars] = 100 [kPa] = 1/10000 [GPa] and p2, p3, p4 are in GPa variable strain equal "(lx - v_L0)/v_L0" variable p1 equal "v_strain" variable p2 equal "-pxx/10000" variable p3 equal "-pyy/10000" variable p4 equal "-pzz/10000" fix def1 all print 100 "${p1} ${p2} ${p3} ${p4}" file Al_comp_100.def1.txt screen no dump 1 all cfg 250 dump.comp_*.cfg mass type xs ys zs c_csym c_peratom fx fy fz # Use cfg for AtomEye software dump_modify 1 element Al thermo 1000 thermo_style custom step v_strain temp v_p2 v_p3 v_p4 ke pe press run 20000
1. In this LAMMPS input, “Initialization” section defines the style of units, the dimension, and initial atomic structure.
2. We need to define the interatomic potentials for various atoms interactions. Simulation is run with the Embedded Atom Model (EAM) interatomic potential in current MD study.
3. It’s now time for simulation to actually run, which begins with the equilibration process. The simulated aluminum sample has to be equilibrated before the deformation at T=300 K and P=0 bar as initial temperature and pressure, respectively.
4. “Deformation section” is last section of the simulation, but not the least. This is where deformation is actually carried out. Different variables such as strain rate, pressures, stress has been defined and then later printed in the log files.
Reference
https://icme.hpc.msstate.edu