argon.rs

// Molecular dynamics simulation of argon gas in the NVE ensemble.

use velvet::prelude::*;

fn main() {
    // Load the argon gas system from a POSCAR formatted file.
    let mut system = Poscar.parse_system_from_file("resources/test/Ar.poscar");

    // Initialize the system temperature using a Boltzmann velocity distribution.
    let boltz = Boltzmann::new(300.0);
    boltz.apply(&mut system);

    // Initialize a Lennard-Jones style pair potential between all Ar-Ar pairs.
    let argon = Species::from_element(Element::Ar);
    let lj = LennardJones::new(4.184, 3.4);

    // Store all of the system's potentials in a Potentials struct.
    let potentials = PotentialsBuilder::new()
        .update_frequency(3)
        .pair(lj, (argon, argon), 8.5, 1.0)
        .build();

    // Initialize a Velocity Verlet style integrator.
    let velocity_verlet = VelocityVerlet::new(0.1);

    // Run MD with no thermostat to simulate the NVE ensemble.
    let md = MolecularDynamics::new(velocity_verlet, NullThermostat);

    // Create an output group which writes scalar properties to a file for post-processing.
    let file_group = RawOutputGroupBuilder::new()
        .destination(std::fs::File::create("argon.txt").unwrap())
        .interval(100)
        .output(PotentialEnergy)
        .output(KineticEnergy)
        .output(TotalEnergy)
        .output(Temperature)
        .build();

    // Build the configuration.
    let config = ConfigurationBuilder::new()
        .raw_output_group(file_group)
        .build();

    // Run the simulation.
    let mut sim = Simulation::new(system, potentials, md, config);
    sim.run(250_000);
}