subject to 𝐴𝒏 = 𝒃 and 𝑛 𝑖 ≥ 0 where 𝐴 is the matrix of the elemental composition of the species and 𝒃 is a vector of the amount of the elements. The chemical potential was calculated using the Gibbs energy of the pure species at the total pressure 𝑝 ∘ (𝜇 𝑖 ∘ ) and the chemical activity (𝑎 𝑖 )