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Working Example

Putting together the blocks introduced in this Starter Pack gives a complete, working exaStamp input file. The example below generates a BCC Tantalum crystal at 600 K with lattice/init_temperature_new, relaxes it towards 300 K under the eam_alloy_force potential with a Langevin thermostat, and periodically writes .xyz snapshots:

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# --- Particles species (see Particles Species) ---
species:
  - Ta: { mass: 180.95 Da, z: 73, charge: 0 e- }

# --- Domain + system setup: BCC lattice at 600 K (see Simulation Domain / Input Data) ---
setup_system:
  - domain:
      cell_size: 3.3 ang
      grid_dims: [ 20, 20, 20 ]
      bounds: [ [ 0 ang, 0 ang, 0 ang ], [ 66 ang, 66 ang, 66 ang ] ]
      periodic: [ true, true, true ]
      expandable: false
  - init_rcb_grid
  - lattice:
      structure: BCC
      types: [ Ta, Ta ]
      size: [ 3.3 ang, 3.3 ang, 3.3 ang ]
  - init_temperature_new:
      T: 600 K

# --- Interatomic potential: EAM alloy, single pass (see Interatomic Potential) ---
eam_alloy_force:
  rcut: 5.30 ang
  parameters:
    file: "Ta1_Ravelo_2013.eam.alloy"

compute_force:
  - eam_alloy_force

# --- Numerical scheme: Langevin NVT, 300 K target (see Numerical Scheme) ---
numerical_scheme: verlet_lnvt

langevin_thermostat:
  T: 300 K
  gamma: 0.1 ps^-1

# --- Global control (see Global Control) ---
global:
  max_iteration: 1000
  dt: 1.0e-3 ps
  rcut_inc: 1.0 ang
  simulation_thermostate_screen_frequency: 10
  simulation_thermostate_file_frequency: 10
  simulation_restart_frequency: 1000
  simulation_snapshot_frequency: 100
  simulation_analysis_frequency: 0

# --- Output: XYZ snapshots (see Output Data) ---
write_snapshot: write_snapshot_xyz

Note

For compactness, domain and init_rcb_grid are nested directly inside setup_system above instead of being declared as separate top-level keys. This is not a problem: the simulation block already calls domain once, earlier in its body, before setup_system runs — nesting a fresh domain: step inside setup_system simply re-invokes that same operator with the full lattice-ready parameters right before init_rcb_grid/lattice need them, overwriting the earlier, auto-deduced values. Both forms are equivalent; keeping everything needed to populate the domain in one place is just easier to read.

Each block maps directly back to the page that introduced it:

Block Covered in
species Particles Species
setup_system (domain, init_rcb_grid, lattice, init_temperature_new) Simulation Domain, Input Data
eam_alloy_force, compute_force Interatomic Potential
numerical_scheme, langevin_thermostat Numerical Scheme
global Global Control
write_snapshot Output Data

Tip

Save this as e.g. ta_bcc.msp and launch it with mpirun -np ${N_MPI} exaStamp ta_bcc.msp (see Running your simulation); it needs the Ta1_Ravelo_2013.eam.alloy parameter file to be available alongside it.