Matthew J. Cliffe, Andrew L. Goodwin
We describe a web-based tool (pascal; principal axis strain calculator) aimed at simplifying the determination of principal coefficients of thermal expansion and com- pressibilities from variable-temperature and variable-pressure lattice parameter data. In a series of three case studies, we use pascal to re-analyse previously-published lat- tice parameter data and show that additional scientific insight is obtainable in each case. First, the two-dimensional metal-organic framework Cu-SIP-3 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 both the strongest negative linear compressibility (NLC) effect yet observed for an oxide framework and also a pressure-induced softening characteristic of an incipient dynamic instability.
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http://arxiv.org/abs/1204.3007
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