Structural Stability of Clean, Passivated, and Partially Dehydrogenated Cuboid and Octahedral Nanodiamonds Up to 2 Nanometers in Size

Abstract

The use of precisely applied mechanical forces to induce site-specific chemical transformations is called positional mechanosynthesis, and diamond is an important early target for achieving mechanosynthesis experimentally. The next major experimental milestone may be the mechanosynthetic fabrication of atomically precise 3D structures, creating readily accessible diamond-based nanomechanical components engineered to form desired architectures possessing superlative mechanical strength, stiffness, and strength-to-weight ratio. To help motivate this future experimental work, the present paper addresses the basic stability of the simplest nanoscale diamond structures-cubes and octahedra-possessing clean, hydrogenated, or partially hydrogenated surfaces. Computational studies using Density Functional Theory (DFT) with the Car-Parrinello Molecular Dynamics (CPMD) code, consuming ∼1,466,852.53 CPU-hours of runtime on the IBM Blue Gene/P supercomputer (23 TFlops), confirmed that fully hydrogenated nanodiamonds up to 2 nm (∼900-1800 atoms) in size having only C(111) faces (octahedrons) or only C(110) and C(100) faces (cuboids) maintain stable sp 3 hybridization. Fully dehydrogenated cuboid nanodiamonds above 1 nm retain the diamond lattice pattern, but smaller dehydrogenated cuboids and dehydrogenated octahedron nanodiamonds up to 2 nm reconstruct to bucky-diamond or onion-like carbon (OLC). At least three adjacent passivating H atoms may be removed, even from the most graphitization-prone C(111) face, without reconstruction of the underlying diamond lattice.

A first‐principles investigation on interactions between various surface‐terminated diamond films

“…When the surface is covered by a monolayer of H atoms, the length of C─C bond increases dramatically to 1.61 Å, 0.23 Å longer than that of the clean surface. The results are quite consistent with those obtained in previous reports . It further confirms the accuracy of the diamond surface model constructed in our work.…”

“…The results are quite consistent with those obtained in previous reports. 33,34 It further confirms the accuracy of the diamond surface model constructed in our work. When the surface is covered by a monolayer of F, OH, or NH 2 , the C─C bond lengths are 1.61, 1.63, and 1.64 Å, respectively, which are very similar to that of H-terminated diamond surface.…”

Nanodiamond for hydrogen storage: Temperature-dependent hydrogenation and charge-induced dehydrogenation

“…[24][25][26] Hydrogenation of nanodiamonds have been studied by different groups, which focus on the size-dependent electronic properties of hydrogen-terminated nanodiamonds and characterisation of hydrogen functionalisation including the hydrogen-assistant separation of the nanodiamond aggregates. [27][28][29][30][31][32][33][34][35][36] It was shown that aggregated nanodiamond powders can be readily hydrogenated through annealing in hydrogen gas at 500 C and 10 À6 mbar, owing to the reconstructed surface with a large number of sp 2 -bonded carbon atoms. 34 The hydrogenation can be also achieved by exposing to microwave hydrogen plasma in the gas phase.…”