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PASCal: a principal axis strain calculator for thermal expansion and compressibility determination

2012/11/15 by Matthew J. Cliffe, Andrew L. Goodwin · 31 citations
Materials Science · Earth and Planetary Sciences · Engineering · #Thermal Expansion and Ionic Conductivity #High-pressure geophysics and materials #Energetic Materials and Combustion

paper · doi:10.1107/s0021889812043026

Abstract

This article describes a web-based tool ( PASCal ; principal axis strain calculator; http://pascal.chem.ox.ac.uk) designed to simplify the determination of principal coefficients of thermal expansion and compressibilities from variable-temperature and variable-pressure lattice parameter data. In a series of three case studies, PASCal is used to reanalyse previously published lattice parameter data and show that additional scientific insight is obtainable in each case. First, the two-dimensional metal–organic framework [Cu 2 (OH)(C 8 H 3 O 7 S)(H 2 O)]·2H 2 O is found to exhibit the strongest area negative thermal expansion (NTE) effect yet observed; second, the widely used explosive HMX exhibits much stronger mechanical anisotropy than had previously been anticipated, including uniaxial NTE driven by thermal changes in molecular conformation; and third, the high-pressure form of the mineral malayaite is shown to exhibit a strong negative linear compressibility effect that arises from correlated tilting of SnO 6 and SiO 4 coordination polyhedra.

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