Lonsdaleite

Lonsdaleite is basically diamond with some bonds rotated such that it is hexagonal (layers ABAB) instead of cubic (layers ABCABC). Natually it occurs only as microscopic crystals. Via mechanosyntheic it will be producible in arbitrary sizes and quantities though just like any other layer pattern like ABCBABCBA or any other gemstone that is supported by the mechanosynthetic cores of the nanofactory at hand.

• Density: 3,2 g/ccm (wikipedia en) 3,3 bis 3,52 g/ccm (wikipedia de)
• Hardness: Mohs 7–8 (for impure specimens) -- (how near to Mohs 10 would be flawless atomically precise mechanosynthesized specimens ?)

Dihedral angles are zero making it a tiny bit higher energy than cubic diamond from that perspective.

Channels

Lonsdaleite as hexagonal diamond has hexagonal channels along its hexagonal main axis.
Very tight though. Very far from the channels in say zeolites.
Mainly hydrogen and helium diffusion or particle beam channeling.

Truning the main axis

For atomically precise gemstone based nanomachinery:
Normal cubic diamond can serve as an intermediate structure
to connect a part of lonsdaleite covaletly and densely to an other part of lonsdaleite
that has its hexagonal main axis facing in a different direction.

Similar principle may apply to other hexagonal or trigonal structure gemstones too.

Related

• Diamond like compounds – (Diamondoid)
• Diamond
• Moissanite

External Links

• https://en.wikipedia.org/wiki/Lonsdaleite
• https://en.wikipedia.org/wiki/Close-packing_of_equal_spheres

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• structue with coordinates
• structue with coordinates (archive)

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• Materials project: https://legacy.materialsproject.org/materials/mp-47/