Space groups of the diamond polytypes

Abstract

Space groups and atomic coordinates for the 4H, 6H, 8H, 10H, 15R, and 21R polytypes of diamond are presented. The systematic method used to determine the highest symmetry space group for diamond polytypes is described.

X‐Ray Induced Synthesis of 8H Diamond

“…We simulated the X-ray diffraction patterns of all possible structural candidates based on SiC polymorphs. [13,14] The simulated X-ray diffraction pattern of the 8H diamond polytype agrees in peak position and intensity with the observed diffraction pattern of the new phase. Each unit cell of 8H diamond consists of 16 carbon atoms stacked as 75% cubic diamond (3C) and 25% lonsdaleite (2H hexagonal diamond) ( Fig.…”

“…The unit cell parameters are fully consistent with the electron diffraction data ( Table 2). The calculated density of 3.67 g cm À3 (after the problems in the crystal structure table are resolved, then this density value might need to be recomputed) is similar to but greater than that of both cubic diamond and lonsdaleite (3.52 g cm À3 ), [3,14] which suggests the existence of compressive stress, as discussed below. Both nanosized particles and compressive stress can produce broadening and slight shifts of the X-ray peaks consistent with the slight mismatch of some peaks in the observed and simulated patterns.…”

“…The diffraction peaks of the new hexagonal carbon phase can be accounted for, and indexed, with a model of the cell of one of the SiC polytypes in which the carbon atoms replace the silicon atoms, making the structure centrosymmetric. [13,14] Accordingly, the corresponding symmetries of these diamond polymorphs can be represented by space group P6 3 /mmc (#194; a supergroup of #186). We simulated the X-ray diffraction patterns of all possible structural candidates based on SiC polymorphs.…”

Facile self-assembly of colloidal diamond from tetrahedral patchy particles via ring selection

“…The two main diamond polytypes, cubic and hexagonal diamond, differ only in a single dimension, and can, in fact, be viewed as the limiting cases of a series of diamond polytype structures ( 32 , 33 ). These different polytype structures can be considered as stacking hybrids of cubic and hexagonal diamond; however, the periodicity of any such polytype can always be described by a hexagonal unit cell ( 33 ).…”

Carbon structures in silicon carbide derived carbon

“…These two types are considered to be the parent diamond structures because any other diamond polytypes are based on combination of layer sequences of 2H or 3C diamond. Other diamond polytypes such as hexagonal 4H, 6H, 8H and 10H and rhombohedral 15R and 21R diamond phases have been theoretically predicted [5,6] and some of them experimentally confirmed (4H, 6H and 8H [7][8][9] 9R and 15R [10,11]). …”