Potential molecular semiconductor devices: Cyclo-C_{: n} (n = 10 and 14) with higher stabilities and aromaticities than acknowledged cyclo-C₁₈

The successful synthesis and isolation of cyclo-C₁₈ in experiments is a ground-breaking development in carbon rings. Herein, we studied the thermodynamic stabilities of cyclo-C_n (4 ≤ n ≤ 34) with hybrid density functional theory. When n = 4N + 2 (N is an integer), cyclo-C_n were thermodynamically stable. In particular, cyclo-C₁₀ and cyclo-C₁₄ were more thermodynamically, kinetically, dynamically, and optically stable compared with the acknowledged cyclo-C₁₈, and were potential candidates for zero-dimensional carbon rings. Cyclo-C_n (n = 10 and 14) show similar molecular semiconductor characteristics to the acknowledged cyclo-C₁₈. The carbon atoms were sp hybridized in cyclo-C₁₀, cyclo-C₁₄, and cyclo-C₁₈. Cyclo-C₁₄ and cyclo-C₁₈ had alternating abnormal single and triple bonds, but cyclo-C₁₀ had equal bonds. Cyclo-C₁₀, cyclo-C₁₄, and cyclo-C₁₈ with large aromaticities had out-of-plane and in-plane π systems, which were perpendicular to each other. The number of π electrons in the out-of-plane and in-plane π systems, respectively, followed the standard Hückel aromaticity rule.