Struct PartitionFunction 

pub struct PartitionFunction {
    pub kind: EnsembleKind,
    pub energy_levels: Vec<f64>,
    pub degeneracies: Vec<f64>,
    pub temperature: f64,
    pub chemical_potential: f64,
    pub particle_numbers: Vec<f64>,
}

Partition function for statistical mechanical ensembles.

Stores a discrete energy spectrum and computes thermodynamic quantities such as free energy, entropy, and average energy.

Fields

kind: EnsembleKind

Ensemble type.

energy_levels: Vec<f64>

Energy levels of the system.

degeneracies: Vec<f64>

Degeneracy of each energy level.

temperature: f64

Temperature in units where k_B = 1.

chemical_potential: f64

Chemical potential (used for grand canonical ensemble).

particle_numbers: Vec<f64>

Particle numbers for each state (grand canonical).

Implementations

impl PartitionFunction

pub fn canonical( energy_levels: Vec<f64>, degeneracies: Vec<f64>, temperature: f64, ) -> Self

Constructs a canonical partition function from energy levels and degeneracies.

Arguments

• energy_levels - Vector of energy eigenvalues.
• degeneracies - Degeneracy of each level (same length as energy_levels).
• temperature - Temperature (k_B = 1 units).

pub fn grand_canonical( energy_levels: Vec<f64>, degeneracies: Vec<f64>, particle_numbers: Vec<f64>, temperature: f64, chemical_potential: f64, ) -> Self

Constructs a grand canonical partition function.

pub fn microcanonical(energy_levels: Vec<f64>, degeneracies: Vec<f64>) -> Self

Constructs a microcanonical partition function (density of states).

pub fn canonical_z(&self) -> f64

Returns the canonical partition function Z = Σ g_i exp(-β E_i).

Returns 0.0 if temperature is non-positive.

pub fn grand_canonical_z(&self) -> f64

Returns the grand canonical partition function Ξ = Σ g_i exp(-β(E_i - μ N_i)).

pub fn density_of_states(&self, target_energy: f64, tolerance: f64) -> f64

Returns the microcanonical density of states Ω(E) for a target energy within tolerance.

Sums degeneracies of levels within ±tolerance of target_energy.

pub fn free_energy(&self) -> f64

Returns the Helmholtz free energy F = -k_B T ln Z (canonical).

pub fn average_energy(&self) -> f64

Returns the average energy ⟨E⟩ = -∂ ln Z / ∂β (canonical).

pub fn entropy(&self) -> f64

Returns the entropy S = (⟨E⟩ - F) / T (canonical).

pub fn heat_capacity(&self) -> f64

Returns the heat capacity C_V = ∂⟨E⟩/∂T = (⟨E²⟩ - ⟨E⟩²) / (k_B T²).

Trait Implementations

impl Clone for PartitionFunction

fn clone(&self) -> PartitionFunction

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for PartitionFunction

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

Formats the value using the given formatter.