Pressure-dependent structural, mechanical, electronic, optical, and thermal properties of fullerene (C₆₀): A first-principles density functional theory study

Fullerene (C₆₀) is a unique carbon nanostructure with strong structural stability, electronic properties, and technological potential in nanotechnology and molecular electronics. In this work, we investigated the pressure-dependent structural, mechanical, electronic, optical, and thermal properties of crystalline fullerene (fullerite) in its face-centered cubic (fcc) phase using DFT over the pressure range 0–25 GPa. The optimized structural parameters obtained with van der Waals corrections were in good agreement with the experimental data, which shows that dispersion interactions are important in molecular crystals. The equation-of-state parameters were found to be 2845 ų and a bulk modulus of 18.1 GPa, suggesting that fullerite is very compressible. All elastic constants were found to be Born-stable in this case, showing that it is very compressible. The bulk modulus increased rapidly with pressure, while compressibility and softness decreased; the lattice stiffened. Electronic structure calculations showed a decrease of the HOMO–LUMO energy gap from 2.24 eV at ambient pressure to 1.72 eV at 25 GPa due to the intermolecular orbital overlap. Also, under greater pressure, the electronegativity and electrophilicity of the electronic transition increased, while electronic hardness decreased, indicating greater electron acceptance and chemical reactivity. Optical properties were dominated by π–π* electronic transitions, which are strong in dielectric and absorption. The specific heat, the Debye temperature, large thermal expansion, and low thermal conductivity were also found in molecular solids. This is an indication that external pressure could help to tune the physical properties of fullerene, which is a promising material in molecular electronics, photovoltaics, sensing, and energy storage.