Predom–Web

Which phase predominates, against two variables

System

Three elements — typically a metal with two non-metals.

Element 1

Element 2

Element 3

Temperature

Units

Or start from an example

Cu–S–O Fe–S–O

Each loads the system and lists its variables, ready to calculate. Cu–S–O at 1000 K is the default example. Case matters: Co is cobalt, CO is not an element.

Axes

Name the elements above, then list the variables. Which ones the axes can show depends on the system, so they come from the calculation rather than from a list held here.

Instructions

First enter three elements — typically a metal with two non-metals — and then set a temperature in the range 273 to 6000 K. Then click SELECT THE AXES and choose a VARIABLE for each axis. For the limits, make sure the minimum is less than the maximum. The step sets where the labels fall on the axis. The default system is Cu–S–O at 1000 K. CALCULATE draws the diagram.

The two axes must be genuinely different variables. P(O) and P(O₂) both fix the chemical potential of oxygen, so a diagram of one against the other has one dimension where it needs two; the form will say so rather than let the calculation fail on it.

About Predom–Web

Predom–Web generates an isothermal predominance area diagram, showing which compound phase is most stable over the ranges you give the two axes. Data are taken from the FACT compound (pure substances) database.

Here you are limited to three elements and to the axis variables the calculation reports for them. In the complete Predom module of the FactSage package you may enter up to three metallic elements, for a multi-metallic system, and any selection of axis variables. Species may be dropped from the calculation; the activity or partial pressure of any compound phase may be set to something other than unity; and the total pressure isobar may be any value. Predom also lists a table of invariant points and performs a detailed equilibrium calculation at any coordinate on the diagram — the invariant points and the point calculation are both offered here.

Predominance area diagrams can also be generated in the Phase Diagram module of FactSage, where non-ideal solutions — slags, alloys, molten salts, mattes, ceramics — may be included from the FACT, SGTE and private solution databases.