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Main Features

  • General features

    • Shared-memory multithreading (OpenMP)
    • Message-passing parallelism (MPI)
    • Graphics Processing Units (GPUs) via CUDA and HIP
    • Can run on a single processor or with MPI only, though multithreading is recommended
    • With MPI, spatial decomposition via Recursive Coordinate Bisection (RCB)
    • Open-source under the Apache License 2.0
    • Highly portable, modular C++20 code built on the Onika/exaNBody framework
    • Entire simulation graph can be user-defined in the input file (simulation block)
    • Easy to extend with new features and functionality
    • Input files use an extended YAML-based format
    • Run one or multiple simulations concurrently from a single script
    • Assign independent resources to run the simulation and perform on-the-fly analysis
    • Large suite of regression tests

  • Particle Types

    • Atomic systems (metals, oxides, ceramics etc...)

    • Rigid molecules (H_2 O, TATB etc...)

    • Flexible molecules (polymers, molecular crystals etc...)

  • Interatomic potentials

    • Pair potentials: Buckingham, Exp-6, Lennard-Jones, ZBL, Morse, tabulated
    • Short-range electrostatics: Coulombic
    • Long-range electrostatics: Ewald, Wolf, reaction-field
    • Many-body potentials: EAM, MEAM
    • Machine-learning interatomic potentials (MLIPs): SNAP, N2P2, ACE
    • Interface to the OpenKIM repository of potentials
    • Bond potentials: harmonic, FENE, Morse, nonlinear, Class II (COMPASS), quartic (breakable), tabulated, scripted
    • Angle potentials:
    • Dihedral potentials:
    • Improper potentials:
    • Hybrid potentials: combine multiple pair, bond, angle, dihedral, and improper terms in a single simulation
    • Overlay potentials: superposition of multiple pair and many-body potentials

  • Particles creation

    • Read external files (.xyz, .data, .mpiio)
    • Create atoms on specific spatial regions
    • Logical operation to define regions and populate them with particles
    • Replication of the system
    • Uniform or gaussian oise on atomic positions, atomic velocities and forces in specific regions

  • Thermodynamic and boundary conditions

    • General triclinic simulation domain
    • Isochoric-isoenergetic (NVE) ensemble
    • Isochoric-isothermal (NVT) ensemble
    • Isobaric-Isothermal (NPT) ensemble
    • Two-temperature model (TTM)
    • Parrinello/Rahman, Nosé-Hoover integrators
    • Region-wise thermostatting of particles
    • Pressure or component-wise stress barostats using Nosé/Hoover
    • Deformation paths formalism for straining the box (any type of deformation can be applied)
    • Periodic, Free, Mirror boundary conditions

  • Time integration

    • Velocity-Verlet integrator
    • User-defined time integrator
    • Rigid body integration for rigid molecules
    • Energy minimization via conjugate gradient and relaxation dynamics

  • Statistics and diagnostics

    • Simulation graph
    • Performance results
    • Highly customizable configuration

  • On-the-fly analysis

    • Particle to grid projection
    • Local average of per-particle field
    • Local structural metrics (entropy, number of neighbors, centrosymmetry, crystal structure classification)
    • Local mechanical metrics (deformation gradient tensor, velocity gradient tensor, slip/twinning system identification)
    • Connected Component Labelling
    • Slice projection and longitudinal profile calculation
    • Histograms
    • Radial distribution function (type-wise)

  • Output

    • Thermodynamic state and logging file
    • Dump output on fixed and variable intervals, based on timestep or simulated time
    • Simulation snapshots (.xyz, .vtk, .vtp) for OVITO and ParaView
    • Binary restart files
    • Per-atom quantities that can be appended to particles in simulation snapshots