Nanocomposite carbon (n-C) films may be described as hybrid materials, consisting of C nanostructures embedded in a host amorphous carbon (a-C) matrix. This form of C offers the unique possibility to intermingle the properties of C nanostructures with those of pure a-C, and thus tailor the mechanical and electronic properties by controlling the type and size of the embedded structures and the hybrid state of the a-C matrix.

Here, I review recent computational work in my group aiming at an accurate atomistic description of n-C films. The methods employed are state-of-the-art Monte Carlo and tight-binding molecular dynamics simulations. Focus is given on two vastly different n-C materials.

The first one consists of diamond nanocrystals in a-C. It is shown [1] that nanodiamonds are stable in only dense, tertrahedral a-C matrices. The films exhibit high strength and hardness, and extreme elastic moduli approaching those of diamond [2], making them ideal for ultrahard coatings and MEMS/NEMS devices. Furthemore, our simulations elucidate for the first time the deformation properties and fracture mechanisms of n-C films.

The second nanomaterial discussed here consists of C nanotubes embedded in low-density a-C matrix [3]. It is shown that van der Waals forces are crucial in shaping up the interfacial geometry, producing a curved graphitic wall surrounding the tubes without direct bonding to the matrix. This might lead to films with excellent thermal and electrical conductivity in the tube direction.

[1] M.G. Fyta, I.N. Remediakis, and P.C. Kelires, Phys. Rev. B 67, 035423 (2003). [2] M.G. Fyta, I.N. Remediakis, P.C. Kelires, and D.A. Papaconstantopoulos, Phys. Rev. Lett. 96, 185503 (2006). [3] M.G. Fyta and P.C. Kelires, Appl. Phys. Lett. 86, 191916 (2005).

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1. Atomistic Models for the Mechanical Response of Nanocrystalline Materials