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arXiv · 1505.02561

Extent of stacking disorder in diamond

Christoph G. Salzmann·Benjamin J. Murray·Jacob J. Shephard
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Abstract

Hexagonal diamond has been predicted computationally to display extraordinary physical properties including a hardness that exceeds cubic diamond. However, a recent electron microscopy study has shown that so-called hexagonal diamond samples are in fact not discrete materials but faulted and twinned cubic diamond. We now provide a quantitative analysis of cubic and hexagonal stacking in diamond samples by analysing X-ray diffraction data with the DIFFaX software package. The highest fractions of hexagonal stacking we find in materials which were previously referred to as hexagonal diamond are below 60%. The remainder of the stacking sequences are cubic. We show that the cubic and hexagonal sequences are interlaced in a complex way and that naturally occurring Lonsdaleite is not a simple phase mixture of cubic and hexagonal diamond. Instead, it is structurally best described as stacking disordered diamond. The future experimental challenge will be to prepare diamond samples beyond 60% hexagonality and towards the so far elusive 'perfect' hexagonal diamond.

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Christoph G. Salzmann, Benjamin J. Murray, Jacob J. Shephard. 2015-05-11. Extent of stacking disorder in diamond. https://doi.org/10.1016/j.diamond.2015.09.007

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