EOS fitting tutorials

Equation-of-state analysis is not one single fit. Quantas distinguishes three scientific domains that answer different questions:

• P–V: how a structure compresses along an isotherm;

• V–T: how a structure expands along an isobar;

• P–V–T: how pressure and temperature act together.

The tutorials below use curated experimental datasets and follow the same sequence in every domain:

1. inspect the input and its uncertainties;

2. choose a physically defensible EOS formulation;

3. choose a regression method consistent with the uncertainty model;

4. validate the complete batch before fitting;

5. preserve every candidate in a native HDF5 archive;

6. inspect parameters, residuals, covariance, and extrapolation;

7. calculate derived properties and generate figures.

The examples deliberately compare several formulations and solvers. The smallest residual is not automatically the best scientific model: parameter stability, uncertainty, correlations, physical limits, and the sampled domain must be considered together.

Recommended order

• Controlling EOS fitting with a batch specification
• P–V tutorial: quartz compression
• V–T tutorial: thermal expansion of rutile
• P–V–T tutorial: coupled EOS of NaF
• EOS diagnostics and calculator
• EOS plotting
• EOS MGD volume-only fitting through the Python API

The first page explains the common batch and solver concepts. The following three pages apply them in P–V, V–T, and P–V–T order.