Defect structures in Frank–Kasper type square–triangle tiling of multimodal cage-type mesoporous silicas. (13th February 2017)

• Record Type: Journal Article
• Authors: Sakamoto, Yasuhiro
• Is Part Of: Journal of physics. Volume 29:Number 12(2017)
• Publication Date: 2017-02-13
• Subjects: mesoporous silica -- electron microscopy -- tetrahedrally close-packed structure -- shield defect -- dodecagonal quasicrystal; Condensed matter -- Periodicals; Matière condensée -- Périodiques; Vaste stoffen; Vloeistoffen; Natuurkunde; Electronic journals; Computer network resources; 530.4105
• DOI: 10.1088/1361-648X/aa5b02
• Languages: English
• ISSNs: 0953-8984

Abstract

Abstract: Multimodal cage-type mesoporous silicas (MCMSs) with Frank–Kasper type square–triangle tiling show a unique defect structure, so-called three-fold symmetric hexagons, or shields, which are caused by phason fluctuations in dodecagonal quasicrystals. We observed and characterized three types of configurations inside shields in both quasiperiodic and periodic 3 2 .4.3.4 tiling of MCMSs by transmission electron microscopy (TEM). The high-resolution TEM images of the shields were well explained by polyhedral models, which are the constituents of the Frank–Kasper type tetrahedrally close-packed structures of MCMSs. Shield defects invariably formed because of mismatch in periodic and/or aperiodic square–triangle tiling, and they were also catalyzed by other defects. Multiple shields overlapped with sharing of 30° rhombus units and showed characteristic motifs in the tiling, such as defect-mediated 12-fold wheel and stripe bundle arrangements. Hence, MCMSs with square–triangle tiling would be governed by a random-tiling-like structure stabilized by entropy rather than energy, which results in defect-free tiling.