Struct Morse 

pub struct Morse;

Morse potential implementation for 1-2 bond stretching.

Physics

Models bond stretching with anharmonicity, allowing for bond dissociation.

• Formula: $$ E = D_e [ e^{-\alpha(R - R_0)} - 1 ]^2 $$
• Derivative Factor (diff): $$ D = \frac{2 \alpha D_e e^{-\alpha(R - R_0)} \left( e^{-\alpha(R - R_0)} - 1 \right)}{R} $$

Parameters

• de: Dissociation energy $D_e$.
• r0: Equilibrium distance $R_0$.
• alpha: Stiffness parameter $\alpha$.

Inputs

• r_sq: Squared distance $r^2$ between two atoms.

Implementation Notes

• Requires sqrt and exp.
• More computationally expensive than Harmonic.

Trait Implementations

impl Clone for Morse

fn clone(&self) -> Morse

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Morse

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

Formats the value using the given formatter.

impl Default for Morse

fn default() -> Morse

Returns the “default value” for a type.

impl<T: Real> PairKernel<T> for Morse

fn energy(r_sq: T, (de, r0, alpha): Self::Params) -> T

Computes only the potential energy.

Formula

$$ E = D_e [ e^{-\alpha(R - R_0)} - 1 ]^2 $$

fn diff(r_sq: T, (de, r0, alpha): Self::Params) -> T

Computes only the force pre-factor $D$.

Formula

$$ D = \frac{2 \alpha D_e e^{-\alpha(R - R_0)} \left( e^{-\alpha(R - R_0)} - 1 \right)}{R} $$

This factor is defined such that the force vector can be computed by a single vector multiplication: $\vec{F} = -D \cdot \vec{r}$.

fn compute(r_sq: T, (de, r0, alpha): Self::Params) -> EnergyDiff<T>

Computes both energy and force pre-factor efficiently.

This method reuses intermediate calculations to minimize operations.

type Params = (T, T, T)

Associated constants/parameters required by the potential (e.g., $k, r_0$).

impl Copy for Morse