Struct BehlerParrinelloDescriptor 

pub struct BehlerParrinelloDescriptor {
    pub eta: Vec<f64>,
    pub rs: Vec<f64>,
    pub cutoff: f64,
}

Behler-Parrinello symmetry functions for constructing atomic descriptors.

Reference: J. Behler and M. Parrinello, PRL 98, 146401 (2007).

Fields

eta: Vec<f64>

Radial decay parameters η for G2 functions.

rs: Vec<f64>

Shift parameters R_s for G2 functions.

cutoff: f64

Cutoff radius R_c in Ångström (or same units as positions).

Implementations

impl BehlerParrinelloDescriptor

pub fn cutoff_fn(r: f64, rc: f64) -> f64

Smooth cutoff function.

f_c(r) = 0.5 * (cos(π r / R_c) + 1) for r < R_c, else 0.

pub fn radial_g1(r: f64, rc: f64) -> f64

G1 radial symmetry function: G1 = f_c(r).

pub fn radial_g2(r: f64, eta: f64, rs: f64, rc: f64) -> f64

G2 radial symmetry function: G2 = exp(-η (r - R_s)²) * f_c(r).

pub fn angular_g4( r_ij: f64, r_ik: f64, r_jk: f64, cos_theta: f64, eta: f64, zeta: f64, lambda: f64, rc: f64, ) -> f64

G4 angular symmetry function (two-body factor for a triplet i-j-k).

G4 = 2^(1-ζ) * (1 + λ cos θ)^ζ * exp(-η (r_ij² + r_ik² + r_jk²)) * f_c(r_ij) f_c(r_ik) f_c(r_jk)

pub fn compute(r_ij: f64, eta: f64, rs: f64, cutoff: f64) -> f64

Compute a single G2 descriptor value (convenience wrapper).

pub fn descriptor_vector( &self, positions: &[[f64; 3]], center_idx: usize, ) -> Vec<f64>

Build a full G2 descriptor vector for atom center_idx.

For every (η, R_s) pair the function sums G2(r_ij, η, R_s, R_c) over all neighbours j ≠ center_idx that lie within the cutoff radius.

Trait Implementations

impl Clone for BehlerParrinelloDescriptor

fn clone(&self) -> BehlerParrinelloDescriptor

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for BehlerParrinelloDescriptor

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.