Multivariable phase diagrams: an algorithm based on generalized thermodynamics

Abstract

By incorporating generalized concepts, the mechanics of phase diagram calculations for multivariable systems have been reduced to a simple algorithm which has been automated with a computer program called Vertex. Vertex is based on an abbreviated combinatorial algorithm which derives a piecewise linear approximation of the isopotential thermodynamic surface for a system. Computations can be terminated at different levels in this sequence to obtain a composition, mixed-variable, or Schreinemakers diagram. It is also possible to trace low variance equilibria between pseudocompounds representing the same phase. The computational variables for Vertex may include related variables such as the composition or activity of a saturated phase (for example, a fluid). A variety of buffering and sectioning constraints can also be imposed within Vertex to simplify the phase diagrams of complex systems. -from Author