A web tool for Principal Axis Strain Calculations

WARNING! A bug in the output meant that the calculated pressure values outputted for the 3rd order BM fits with a critical pressure were incorrect. This did not affect the refined parameters or the displayed graph.
Quick Guide. Technical information and caveats. More information available on mouseover.

Data type:
Temperature (K) Pressure (GPa)

Phase transition:If the phase has a phase transition between ambient pressure and the first data point. These options have no effect for temperature data and can be left blank.
Use a critical pressure?:
Critical pressure:

Advanced Options:
Finite strains are more appropriate for large strains. The derivation of the Birch-Murnaghan EoS uses finite Eulerian strain.

Finite strain?
Eulerian strain?

Data:One phase only
T or PK or GPaσ(T or P)K or GPaabcαβγ

PASCal is currently operating in light mode. Instructions on how to generate graphical output is available from
We hope to restore full functionality at a future date.
Developed by Matthew Cliffe and Andrew Goodwin at the University of Oxford.
Any queries or comments to matthew[dot]cliffe[at]nottingham[dot]ac[dot]uk and Andrew[dot]Goodwin[at]chem[dot]ox[dot]ac[dot]uk.
Please cite M.J. Cliffe and A.L. Goodwin, J. Appl. Cryst. (2012). 45, 1321-1329.
A preprint of the paper is also available at the arXiv.