Calculational aspects

The technique employed by ChemApp to calculate complex, multicomponent, multiphase chemical equilibria is called Gibbs energy minimisation (GEM). An outline of this technique can be found in an article on ChemSage, which internally uses the same calculational engine as ChemApp [Eri90]. More information on the GEM technique can be obtained from the following references –   [Smi82] – W. R. […]

Two main reasons can be given which are responsible for ChemApp’s speed: The GEM code has been under constant development for the last 30 years, since the days of SOLGASMIX. Along with the robustness of the code, its speed has always had a high priority. When ChemApp begins an equilibrium calculation, it tries to guess

ChemApp itself does not contain any code to deal with kinetic issues, but the fact that ChemApp is available as an independent library makes it ideal to be used in programs that deal with these issues. In these cases, ChemApp is used to calculate a local equilibrium (“local” either meaning “local in time”, or “local

Although ChemApp calculates even complex equilibria remarkably fast (see section 6.2), “speed” is always a relative thing. If one is frequently doing 100000 equilibrium calculations in a row as part of a simulation program, one is interested in every possible technique that saves computation time. Here are a few techniques that help speeding up the calculations.