Hexagonal stacking

The As atoms form close-packed layers in the hexagonal stacking sequence. .. BC. The Ni atoms (on sites A) are placed in the centres of all the octahedral interstices in the As layers. Ni has 6 As neighbours and As is surrounded by 6 Ni (forming a right trigonal prism). 

The original members of the M41S family consisted of MCM-41 (hexagonal phase) (Figure 2.23), MCM-48 (cubic Ia3d phase), and MCM-50 (a stabilized lamellar phase) [110,111,117], The structure of MCM-41 has a hexagonal stacking of uniform diameter porous tubes, whose size can vary from about 15 A to more than 100 A [111,117],... 

Figure 8.8. Two-dimensional array of Pt nanocrystals, (a) TEM image of thiol-deriva-tized Pt nanocrystals. Flexagonal particles form honeycomb-like arrays, (b) STM image showing the hexagonal stacking of the top three layers (reproduced with...

Tetragonal, with c.c.p. Cl-—[MnCl6] octahedra share five edges and one corner Both c.c.p. and hexagonal stacking of Cl-, Mn in J of octahedral sites... 

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