Matrix model

.matrix encodes an alternative formulation of the Pitzer model, using matrix mathematics instead of loops to cycle through the different combinations of solutes.

This version of the code runs much faster than the equivalent .model functions for a single solution. It therefore more suitable for using in the equilibration solver. However, if some property is being evaluated for many different solutions without the need for equilibrium calculations, then the functions in .model will probably run faster.

.assemble - prepare for matrix calculation

Generates coefficient matrices needed for the Pitzer model functions in this module.

Syntax:

allmxs = pz.matrix.assemble(ions, tempK, pres, cflib=Seawater)

Inputs:

• ions - list of ions, as described in the import/export documentation;
• tempK - a single temperature in K;
• pres - a single pressure in dbar;
• cflib - a coefficient library (optional, defaults to Seawater).

Outputs:

Every matrix required as an input to the model functions in this module.

Model functions

All other functions in this module will be the matrix equivalents of the functions with the same names in the main model, although so far only the following have been added:

• ln_acfs - natural logarithm of the solute activity coefficients;
• acfs - solute activity coefficients;
• ln_aw - natural logarithm of the water activity;
• aw - water activity.

Syntax:

var = pz.matrix.var(mols, allmxs)

The input allmxs is generated using pz.matrix.assemble (see above).