arXiv subjects

P. C. Kelires

Publications and source records attributed to P. C. Kelires.

3 recordsLinked to original sources

arXiv2007

Probing the sp^2 dependence of elastic moduli in ultrahard diamond films

The structural and elastic properties of diamond nanocomposites and ultrananocrystalline diamond films (UNCD) are investigated using both empirical potentials and tight binding schemes. We find that both materials are extremely hard, but their superb diamondlike properties are limited by their sp^2 component. In diamond composites, the sp^2 atoms are found in the matrix and far from the interface with the inclusion, and they are responsible for the softening of the material. In UNCD, the sp^2 atoms are located in the grain boundaries. They offer relaxation mechanisms which relieve the strain but, on the other hand, impose deformations that lead to softening. The higher the sp^2 component the less rigid these materials are.

cond-mat.mtrl-sci↗

arXiv2005

Simulations of composite carbon films with nanotube inclusions

We study the interfacial structure, stability, and elastic properties of composite carbon films containing nanotubes. Our Monte Carlo simulations show that Van der Waals forces play a vital role in shaping up the interfacial geometry, producing a curved graphitic wall surrounding the tubes. The most stable structures are predicted to have intermediate densities, high anisotropies, and increased elastic moduli compared to pure amorphous carbon films.

cond-mat.mtrl-sci↗

arXiv2000

Thermodynamics of C incorporation on Si(100) from ab initio calculations

We study the thermodynamics of C incorporation on Si(100), a system where strain and chemical effects are both important. Our analysis is based on first-principles atomistic calculations to obtain the important lowest energy structures, and a classical effective Hamiltonian which is employed to represent the long-range strain effects and incorporate the thermodynamic aspects. We determine the equilibrium phase diagram in temperature and C chemical potential, which allows us to predict the mesoscopic structure of the system that should be observed under experimentally relevant conditions.

cond-mat.mtrl-sci↗