Function evaluate_displacements_parallel 

pub fn evaluate_displacements_parallel<F>(
    displacements: &[Vec<[f64; 3]>],
    energy_fn: F,
) -> Vec<f64>
where
    F: Fn(&[[f64; 3]]) -> f64 + Sync,

Batch-evaluate energies for displaced geometries using parallel CPU.

energy_fn: closure that computes energy for a given geometry. displacements: list of displaced geometries.