Results of a series of molecular dynamics simulations of cubic siliceous zeolites suggest that pressure-induced softening—the phenomenon in which a material becomes progressively more compressible under pressure—is likely to be a common feature of framework materials that show negative thermal expansion. The correlation between the negative thermal expansion and the pressure-induced softening is investigated on the basis of thermodynamics.

• Received 14 January 2013

DOI:https://doi.org/10.1103/PhysRevB.87.214109