Struct CosineLinear 

pub struct CosineLinear;

Cosine Linear potential for bond angles with linear equilibrium geometry.

Physics

Models the angle bending energy for atoms with linear equilibrium geometry ($\theta_0 = 180°$), using a simple linear function of the cosine of the angle.

• Formula: $$ E = C (1 + \cos\theta) $$
• Derivative Factor (diff): $$ \Gamma = \frac{dE}{d(\cos\theta)} = C $$

Parameters

• c: Force constant $C$.

Inputs

• cos_theta: Cosine of the bond angle $\theta_{ijk}$.

Implementation Notes

• Single multiply-add for energy; zero arithmetic for derivative.
• Pure polynomial evaluation; no trigonometric functions required.
• Branchless and panic-free.

Trait Implementations

impl<T: Real> AngleKernel<T> for CosineLinear

fn energy(cos_theta: T, c: Self::Params) -> T

Computes only the potential energy.

Formula

$$ E = C (1 + \cos\theta) $$

fn diff(_cos_theta: T, c: Self::Params) -> T

Computes only the derivative factor $\Gamma$.

Formula

$$ \Gamma = C $$

This factor allows computing forces via the chain rule: $$ \vec{F} = -\Gamma \cdot \nabla (\cos\theta) $$

fn compute(cos_theta: T, c: Self::Params) -> EnergyDiff<T>

Computes both energy and derivative factor efficiently.

This method reuses intermediate calculations to minimize operations.

type Params = T

Associated constants/parameters required by the potential (e.g., $C, \theta_0$).

impl Clone for CosineLinear

fn clone(&self) -> CosineLinear

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for CosineLinear

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

Formats the value using the given formatter.

impl Default for CosineLinear

fn default() -> CosineLinear

Returns the “default value” for a type.

impl Copy for CosineLinear