Nanodiamond clusters are ubiquitous products of detonation, and are therefore relatively cheap and plentiful. Because of their potentially unique properties, they have been targeted for a number of applications. These applications include efficient electron field-emitters and quantum dots whose electronic properties could be tuned via surface chemisorption. To explore the properties of these structures for nanotechnology applications, the vibrational density of states, heat capacity and electronic structure of nanodiamond clusters containing between 34 and 1,600 carbon atoms were calculated using an analytic potential, and tight-binding and ab-initio Hamiltonians. All clusters had shapes represented by an octahedron with (111) facets with the top and the bottom vertices truncated to introduce (100) surfaces. The tight-binding Hamiltonian consisted of environment-dependent matrix elements, and C-H parameters fit to reproduce energy states of cyclic C6 and ethane. Both tight-binding and O(N) ab-initio methods were used to produce the local density of states and potential distribution. The calculations predict an electronic density of states similar to bulk diamond for clusters with characteristic size greater than ~2.5 nm, and insignificant differences in the potential distribution between the clusters and bulk diamond for sizes greater than ~1 nm. Hydrogen passivated nanodiamond clusters are estimated to have an electron affinity ranging between -1.8 eV and -1.1 eV depending on the surface reconstruction type.
Denis A. Areshkin
Department of Materials Science and Engineering, North Carolina State University
Raleigh, NC 27695-7907 USA