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Diaphite-structured nanodiamonds with six- and twelve-fold symmetries

Accepted version
Peer-reviewed

Type

Article

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Authors

Németh, P 
McColl, K 
Garvie, LAJ 
Salzmann, CG 
Pickard, CJ 

Abstract

Nanodiamonds (ND) with 1-5 nm dimensions found in meteorites or produced by chemical vapour deposition (CVD) and detonation synthesis are typically described in terms of an sp3-bonded carbon network. However, ultra-high-resolution transmission electron microscopy (uHRTEM) combined with density functional theory (DFT) modelling leads to a different structural interpretation. uHRTEM imaging and nanodiffraction studies of many NDs show six-fold symmetry features whose identity has long been controversial. We also observe diffraction patterns with twelve equally-spaced and symmetrically but unequally arranged reflections, indicating structures with crystallographically- forbidden ideal and distorted twelve-fold symmetry. Structural models based on our DFT calculations lead to an interpretation of these unusual features found throughout the meteoritic and CVD samples in terms of sp3 domains arranged around and coherently bonded to graphitic domains embedded within the diamond matrix. The bonding at the sp2-sp3 interface can explain the unusual features observed in electron energy-loss spectra (EELS) below the onset of the main diamond C1s core-loss edge leading to predictions of low-dimensional conductivity behaviour. The presence of sp2- as well as sp3-bonded regions allows us to interpret previously unexplained features of the Raman spectra and EELS data of ND materials.

Description

Keywords

Nanodiamonds, Diaphite, Ultra-high-resolution TEM, Density functional calculations, Six-and twelve-fold symmetries, sp(2)-and sp(3)-bonded nanomaterials

Journal Title

Diamond and Related Materials

Conference Name

Journal ISSN

0925-9635
1879-0062

Volume Title

119

Publisher

Elsevier BV
Sponsorship
Engineering and Physical Sciences Research Council (EP/P022596/1)
European Commission Horizon 2020 (H2020) Future and Emerging Technologies (FET) (785219)
European Commission Horizon 2020 (H2020) Future and Emerging Technologies (FET) (881603)