[−]Trait lumol::GlobalPotential

pub trait GlobalPotential: GlobalCache + BoxCloneGlobal + Send + Sync {
    fn cutoff(&self) -> Option<f64>;
    fn energy(&self, configuration: &Configuration) -> f64;
    fn forces(&self, configuration: &Configuration, forces: &mut [Vector3D]);
    fn atomic_virial(&self, configuration: &Configuration) -> Matrix3;

    fn molecular_virial(&self, configuration: &Configuration) -> Matrix3 { ... }
}

A potential acting on the whole System at once.

This kind of potential is passed all the data in a system and returns the energy/forces/virial contribution for this potential. It has three main usages:

Potentials that does not fit the pair/bond/angle/dihedral framework for potentials: the coulombic potential solver is the more important example;
External potentials like an external electric field or a hard wall;
Potentials coming from external software: DFT computations, metadynamic drivers, or other.

Examples

use lumol_core::energy::{GlobalPotential, GlobalCache};
use lumol_core::types::{Vector3D, Matrix3};
use lumol_core::sys::{System, Configuration, Particle, Molecule, UnitCell};

/// Shift the energy of all the particles by a given delta.
#[derive(Clone)]
struct ShiftAll {
    delta: f64,
}

impl GlobalPotential for ShiftAll {
    fn cutoff(&self) -> Option<f64> {
        None
    }

    fn energy(&self, configuration: &Configuration) -> f64 {
        // shift all particles by delta
        self.delta * configuration.size() as f64
    }

    fn forces(&self, configuration: &Configuration, forces: &mut [Vector3D]) {
        // this potential does not changes the forces
    }

    fn atomic_virial(&self, configuration: &Configuration) -> Matrix3 {
        // the virial is null as all the forces are null
        Matrix3::zero()
    }
}

// Not implementing `GlobalCache` means that we will not be able to use
// `ShiftAll` in Monte Carlo simulations.
impl GlobalCache for ShiftAll {
    fn move_molecule_cost(&self, _: &Configuration, _: usize, _: &[Vector3D]) -> f64 {
        unimplemented!()
    }

    fn update(&self) {
        unimplemented!()
    }
}

// A simple test
let mut system = System::with_cell(UnitCell::cubic(10.0));
system.add_molecule(Molecule::new(Particle::new("Ar")));
system.add_molecule(Molecule::new(Particle::new("Ar")));

system.add_global_potential(Box::new(ShiftAll{delta: 1.0}));

assert_eq!(system.potential_energy(), 2.0);
assert_eq!(system.forces(), vec![Vector3D::zero(); 2]);
assert_eq!(system.virial(), Matrix3::zero());

Required methods

`fn cutoff(&self) -> Option<f64>`

Return the cut off radius.

`fn energy(&self, configuration: &Configuration) -> f64`

Compute the energetic contribution of this potential

`fn forces(&self, configuration: &Configuration, forces: &mut [Vector3D])`

Compute the force contribution of this potential. This function should return a vector containing the force acting on each particle in the configuration.

`fn atomic_virial(&self, configuration: &Configuration) -> Matrix3`

Compute the total virial contribution of this potential, using the atomic virial definition

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Provided methods

`fn molecular_virial(&self, configuration: &Configuration) -> Matrix3`

Compute the total virial contribution of this potential, using the molecular virial definition. This default to atomic_virial.

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Implementors

`impl GlobalPotential for SharedEwald`

`pub fn cutoff(&self) -> Option<f64>`

`pub fn energy(&self, configuration: &Configuration) -> f64`

`pub fn forces(&self, configuration: &Configuration, forces: &mut [Vector3D])`

`pub fn atomic_virial(&self, configuration: &Configuration) -> Matrix3`

`pub fn molecular_virial(&self, configuration: &Configuration) -> Matrix3`

`impl GlobalPotential for Wolf`

`pub fn cutoff(&self) -> Option<f64>`

`pub fn energy(&self, configuration: &Configuration) -> f64`

`pub fn forces(&self, configuration: &Configuration, forces: &mut [Vector3D])`

`pub fn atomic_virial(&self, configuration: &Configuration) -> Matrix3`

`pub fn molecular_virial(&self, configuration: &Configuration) -> Matrix3`

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