Struct Opls 

pub struct Opls<T> { /* private fields */ }

OPLS Fourier series torsion potential.

Parameters

• c1, c2, c3, c4: Fourier coefficients (energy units)

Precomputed Values

• offset: Stores c1 + c2 + c3 + c4 for efficient computation

Implementations

impl<T: Vector> Opls<T>

pub fn new(c1: f64, c2: f64, c3: f64, c4: f64) -> Self

Creates a new OPLS torsion potential.

Arguments

• c1, c2, c3, c4: Fourier coefficients

Example

use potentials::torsion::Opls;

// Typical alkane torsion
let torsion = Opls::<f64>::new(0.7, 0.1, 1.5, 0.0);

pub fn simple(c1: f64, c3: f64) -> Self

Creates with only n=1 and n=3 terms (common case).

pub fn threefold(c3: f64) -> Self

Creates with only n=3 term (pure three-fold).

Trait Implementations

impl<T: Clone> Clone for Opls<T>

fn clone(&self) -> Opls<T>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T: Debug> Debug for Opls<T>

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

Formats the value using the given formatter.

impl<T: PartialEq> PartialEq for Opls<T>

fn eq(&self, other: &Opls<T>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: Vector> Potential4<T> for Opls<T>

fn energy(&self, cos_phi: T, _sin_phi: T) -> T

Computes the potential energy.

V = offset + c1*cos(phi) - c2*cos(2phi) + c3*cos(3phi) - c4*cos(4phi)

Uses Chebyshev polynomials for cos(n*phi):

• cos(2phi) = 2*cos^2(phi) - 1
• cos(3phi) = 4cos^3(phi) - 3cos(phi)
• cos(4phi) = 8cos^4(phi) - 8cos^2(phi) + 1

fn derivative(&self, cos_phi: T, sin_phi: T) -> T

Computes dV/d(phi).

dV/dphi = -c1*sin(phi) + 2*c2*sin(2phi) - 3*c3*sin(3phi) + 4*c4*sin(4phi)

fn energy_derivative(&self, cos_phi: T, sin_phi: T) -> (T, T)

Computes energy and derivative together (optimized).

Shares the computation of cos^n and sin(n*phi) terms.

impl<T: Copy> Copy for Opls<T>

impl<T> StructuralPartialEq for Opls<T>