# An open source webtool for calculating compressibilities & thermal expansion

Sun, Oct 22, 2023*Figure: PASCal Logo shows an indicatrix, which plots the anisotropy of response of a crystal.*

This paper describes the newest version of PASCal, a simple webtool designed to calculate the principal thermal expansivities, compressibilities or response to electrochemical strain of a system from lattice parameters. For low symmetry crystals, the arbitrary choice of unit cell means that if you only look at the cell lengths, it is possible to miss interesting features in the (thermo)mechanical behaviour of a crystal, for example negative thermal expansion or negative compressibilities. PASCal is designed to be an easy method for calculating the principal strain values that give the complete description of these systems. The new version is completely open source, available offline and includes electrochemical strain.

**One of the authors of this work, Monthakan, was a summer student in the group where this was her project!**

### Paper

PASCal Python: A Principal Axis Strain Calculator

M Lertkiattrakul, M L Evans, M J Cliffe

*JOSS*, **8**, 5556 (2023).