CALPHADtype

CALPHADtype is a designation used in CALPHAD-based thermodynamic modeling to indicate the mathematical form of a phase’s thermodynamic description. It signals how the Gibbs free energy of the phase is represented and which parameters and constraints apply during calculations of phase diagrams.

Common CALPHADtype categories include substitutional solutions, interstitial solutions, compound energy formalism (CEF) models, and stoichiometric or line compounds. Substitutional solution models describe solid solutions where lattice sites are occupied by substituting elements. Interstitial solution models account for small atoms occupying interstitial sites within a host lattice. Compound energy formalism (CEF) uses a multi-sublattice framework with site fractions to describe complex intermetallics and compounds with defined crystal structures. Stoichiometric or line compounds represent phases with fixed compositions or narrowly defined ranges.

Other variants may include molecular or complex compound descriptions and specialized ordered-disordered or multi-component configurations. In practice, CALPHADtype guides the organization of thermodynamic data, the form of the Gibbs energy expression, and the parameter set used during phase equilibrium calculations. It helps database builders and software parse inputs, validate data, and perform consistent calculations across phases.

Notes: CALPHADtype conventions can vary between databases and software packages, and there is not a universal standard. Users should consult the documentation of their specific CALPHAD database or software to understand the exact meaning and allowed values of CALPHADtype in that context.