Fivefold twinning of diamond

Twinning in natural melilite simulating a fivefold superstructure.

Additional reflections seemingly leading to a tetragonal fivefold supercell have been observed in a number of melilites. A careful examination of the collected intensity data reveals that this feature is due to the coexistence of two twin domains related by a (120) twin plane. Reflections of the first domain (I) with h(b)(2) + k(b)(2) = 5n overlap those of the second domain (II) when both the f...

Twinning of cubic diamond explains reported nanodiamond polymorphs

The unusual physical properties and formation conditions attributed to h-, i-, m-, and n-nanodiamond polymorphs has resulted in their receiving much attention in the materials and planetary science literature. Their identification is based on diffraction features that are absent in ordinary cubic (c-) diamond (space group: Fd-3m). We show, using ultra-high-resolution transmission electron micro...

On Nodal Sextic Fivefold

In this paper we prove the birational superrigidity and nonrationality of a hypersurface X ⊂ P of degree 6 such that the hypersurface X does not contain three-dimensional linear subspaces of P and the only singularities of X are isolated ordinary double points.

A mechanism for crystal twinning in the growth of diamond by chemical vapour deposition.

A model for the formation of crystal twins in chemical vapour deposited diamond materials is presented. The twinning mechanism originates from the formation of a hydrogen-terminated four carbon atom cluster on a local {111} surface morphology, which also serves as a nucleus to the next layer of growth. Subsequent growth proceeds by reaction at the step edges with one and two carbon atom-contain...

Incoherent structural relaxation of fivefold twinned nanowires