Physicochemical characterization of a new porous 2D semiconductor carbon allotrope, C ₁₆ : an investigation via density functional theory and machine learning-based molecular dynamics

This study comprehensively characterizes, with suggested applications, a novel two-dimensional carbon allotrope, C₁₆, using density functional theory and machine learning-based molecular dynamics. This nanomaterial is derived from naphthalene and bicyclopropylidene molecules, forming a planar configuration with sp² hybridization and featuring 3-, 4-, 6-, 8-, and 10-membered rings. The cohesive energy of -7.1 eV per atom, the absence of imaginary frequencies in the phonon spectrum, and the retention of the system's topology after ab initio molecular dynamics simulations confirm the structural stability of C₁₆. The nanomaterial exhibits a semiconducting behavior with a direct band gap of 0.59 eV and anisotropic optical absorption in the y direction. Assuming a complete absorption of incident light, it registers a power conversion efficiency of 13%, demonstrating relatively good potential for applications in solar energy conversion. Excluding the vacuum effect along the non-periodic z direction, the planar lattice thermal conductivity κ_L reaches ultralow values of 1.90 × 10^-2 W (m K)^-1, 0.90 × 10^-2, and 0.59 × 10^-2 for T = 300 K, 600 K, and 1000 K, respectively along both x and y directions. Very close to the Fermi level, the thermoelectric figure of merit (zT) can reach a maximum value of 0.93 at room temperatures along both planar directions, indicating an excellent ability to convert a temperature gradient into electrical power. Additionally, C₁₆ demonstrates high mechanical strength, with Young's modulus values of 500 GPa and 630 GPa in the x and y directions, respectively. Insights into the electronic, optical, thermoelectric, and mechanical properties of C₁₆ reveal its promising capability for energy conversion applications.