Thermodynamic behavior of the carbon schwarzite fcc (C-36)(2)

The thermodynamic behavior of the carbon schwarzite fcc (Formula presented) has been studied by tight-binding molecular-dynamics simulations at constant temperature and pressure. The system is totally (Formula presented) bonded and it can be represented as a folded graphite sheet made by hexagonal and heptagonal rings. The structure has a density (Formula presented) as low as (Formula presented) at (Formula presented) K and a bulk modulus B, evaluated by measuring the volume variation upon application of an external hydrostatic load, as large as (Formula presented) Mbar. At (Formula presented) K, the structure unfolds via a topological transformation, which brings the value of the topological connectivity of the structure (Formula presented) from (Formula presented) (for a cell including four molecules) to (Formula presented) (which is the value of a graphite sheet). The behavior of the structural, dynamical, and electronic-structure properties has been evaluated in the whole temperature range, below and above the temperature of the topological transition.