Negative Poisson's ratios in siliceous zeolite MFI-silicalite

Abstract

Brillouin scattering measurements of the single-crystal elastic properties of the as-made zeolite silicalite ∫ (C3 H7)4 NF∫4 [Si96 O192] -MFI provides the first experimental evidence for on-axis negative Poisson's ratios (auxeticity) in a synthetic zeolite structure. MFI laterally contracts when compressed and laterally expands when stretched along x1 and x2 directions in the (001) plane (12 =-0.061, 21 =-0.051). The aggregate Poisson's ratio of MFI, although positive, has an anomalously low value =0.175 (3) compared to other silicate materials. These results suggest that the template-free MFI-silicalite [Si96 O192] might have potential applications as tunable sieve where molecular discriminating characteristics are adjusted by application of stress along specific axes. © 2008 American Institute of Physics.