TY - JOUR
T1 - Defect structures in Frank-Kasper type square-triangle tiling of multimodal cage-type mesoporous silicas
AU - Sakamoto, Yasuhiro
N1 - Funding Information:
This work was supported by PRESTO, Japan Science and Technology Agency (JST). We are grateful to Prof Shunai Che, Dr Chuanbo Gao (Shanghai Jiao Tong University, Shanghai, Peoples Republic of China), and Prof Osamu Terasaki (Stockholm University, Stockholm, Sweden) for providing samples and helpful discussion.
Publisher Copyright:
© 2017 IOP Publishing Ltd.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2017/2/13
Y1 - 2017/2/13
N2 - 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 32.4.3.4 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.
AB - 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 32.4.3.4 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.
KW - dodecagonal quasicrystal
KW - electron microscopy
KW - mesoporous silica
KW - shield defect
KW - tetrahedrally close-packed structure
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U2 - 10.1088/1361-648X/aa5b02
DO - 10.1088/1361-648X/aa5b02
M3 - Article
AN - SCOPUS:85013195117
VL - 29
JO - Journal of Physics Condensed Matter
JF - Journal of Physics Condensed Matter
SN - 0953-8984
IS - 12
M1 - 124002
ER -