Variable particle-number ensemble: P(N, E_i) ∝ exp[-β(E_i - μN)]/Ξ. Grand-potential Ω = -k_BT ln Ξ; mean particle-number ⟨N⟩ = ∂ln Ξ/∂(βμ). Used for adsorption isotherms (BET / Langmuir derived), open chemical systems, electrochemistry.
Variable particle-number ensemble: P(N, E_i) ∝ exp[-β(E_i - μN)]/Ξ. Grand-potential Ω = -k_BT ln Ξ; mean particle-number ⟨N⟩ = ∂ln Ξ/∂(βμ). Used for adsorption isotherms (BET / Langmuir derived), open chemical systems, electrochemistry.