Comprehensive Survey of the Structures of C4, C4−, and C4+ Clusters

Abstract Historic debates on the true structure of C 4 cluster based on the experimental results of EPR, infrared spectroscopy and Coulomb explosion, as well as theoretical calculations have prompted us to comprehensively survey the geometries of C 4 clusters. A total of 37 possible geometries for neutral C 4 , 24 C 4 anions (C 4 − ) and 27 C 4 cations (C 4 + ) have been optimized with both MP2 and density functional theory (B3LYP) calculations and verified with subsequent frequency calculations. The results align very well with all experimental observations, including the detection of rhombic C 4 structure in Coulomb explosion experiment and the cis‐bent structure, in addition to the most stable linear geometries for C 4 and C 4 − , and the electron affinity and ionization potential of C 4 .