The calculation of chemical equilibria in complex systems, i.e. systems with many elements and many phases - some or all of which may be nonideal mixtures - can only be performed rigorously by minimization of the total Gibbs energy of the system. This requires the compulsory use of numerical methods to solve multi-variable, transcendental equation systems.
Additionally, in order to make such thermochemical calculations a basic tool in the development and optimization of materials and processes of many different types, high quality thermochemical databases for a wide variety of inorganic systems need to be available.
The Institute of Theoretical Metallurgy (now Materials Chemistry) at RWTH Aachen University had been involved since the 1970s in this field of research, and the work has been continued and expanded at its spin-off GTT-Technologies (Gesellschaft für Technische Thermochemie und -physik mbH) since 1983.
Today, a number of software tools based on Gibbs energy minimization are available from GTT-Technologies which are used worldwide in application areas such as metallurgy and alloy development, aqueous chemistry, nuclear materials, combustion technology, ceramics and refractory technology, geochemistry, corrosion, and many more.