MTDATA – Phase Diagram Software from the National Physical Laboratory







Training and Support 




Other Services 





Thermodynamic models in MTDATA

The temperature and pressure dependence of the Gibbs energy and interactions between the constituents of solution phases are described by mathematical models. Those used in MTDATA are well established in the scientific literature and are supported to varying degrees by a body of data. They are incorporated in a modular way into the software and data structures. The models are closely linked to the phase type. They include:

  • A system for describing the temperature dependence of the Gibbs energy either directly or via equations for the heat capacity. The format has the flexibility to deal with all the equations normally used for representing the temperature dependence of the Gibbs energy for pure substances, other unary data and data for mixing.
  • The Murnaghan model for the thermodynamic data as a function of pressure.
  • The Inden model for magnetic contributions.
  • The compound energy model allowing solution on the individual sublattices of crystalline compounds.
  • The associated solution model for liquids in which there is strong bonding between the components, the bonding having a significant covalent character.
  • The two-sublattice ionic liquid model used for molten salts and other mainly ionic systems.
  • The extended Redlich-Kister model for predicting the multicomponent thermodynamic data of non-ideal solutions including those on individual sublattices.
  • An extended Kapoor-Frohberg model for slags.
  • The Quasi-chemical model
  • The ideal, Debye-Hückel and Pitzer models for aqueous solutions
  • The chemical ordering model
  • The Flory-Huggins model for polymer blends
  • An organic model suitable for molecules for which full experimental data are unavailable
Some of these models are exclusive to particular databases but others, for example the Redlich-Kister model for interactions in non-ideal solutions, are used in a number of databases and are included, for example, in the compound energy and associated solution models. Others are more specific and have been included to ensure that MTDATA subscribers are able to use data that meets their needs.

Back to WinMT Help start

Updated 7 May 2010