Theoretical study on the structural, electronic, and optical properties of BnCn (n=1-13) clusters

We applied density functional theory (DFT) calculations to investigate the low-energy geometries and electronic characteristics of stoichiometric BnCn (n = 1-13) clusters. We performed harmonic vibration frequency analysis to ensure that the ground-state isomers are the real local minima. BnCn clusters tend to evolve from planar and annular structures to quasiplanar bowl structures to maintain the lowest structural energy as cluster size n increases. The clusters with even n have large HOMO-LUMO gaps and high stability. We used the time-dependent DFT (TDDFT) calculations to acquire the optical absorption spectra for the lowest-energy BnCn (n = 4, 6, 8, 10, 12) clusters. The clusters exhibit strong absorption in the ultraviolet region. With the increasement of n, the absorption of clusters, particularly that of the B8C8 cluster, intensifies in the visible region. Therefore, the clusters investigated in this work can be used to fabricate novel two-dimensional materials for visible-light absorption and have potential applications in various fields, such as catalysis.