Figure 4

Diamond nanocrystals with rectangular 0.206-nm fringes (white lines).

(a) HRTEM image of a grain from the CVD-produced sample. Corresponding FFT (insert) shows two sets of 0.206-nm {111} diffraction spots that indicate domains (i, ii) that are rotated 90° with respect to each other along <011>. (b) Structure model showing two domains of a 90º rotation twin. Black lines mark perpendicular {111} planes. The domain boundaries of the twin structure consist of five-, six- and seven-member carbon rings. The sketch of the diffraction pattern of the 90° rotation twin (insert) shows two sets of {111} diffraction spots. Domain i and ii as well as their corresponding diffraction spots are marked with grey and black balls, respectively. (c) Grain from the CVD-produced sample (d,e) Grains from the the Orgueil meteorite. Domain misorientation (tilt from <011> zone axis) results in one set of 111 diffraction spots in FFTs (c,d,e). The FFT suggests that (d) consists of three domains (white arrow) from which two are related to 90° rotation.