Theoretical study of AlC3: linear or cyclic ground state?

A theoretical study of the AlC3 species has been carried out. There are three species that lie quite close in energy: a rhombic four-membered ring, 1(2A1), a T-shape structure, 2(2B2), and a linear species, 3(2Π). The linear isomer is predicted to be lower in energy, but 1(2A1) lies only about 1–2 kcal mol−1 higher. In any case, it seems that both isomers could be accesible to experimental detection. Our conclusion is in contrast with a previous theoretical study on this system that predicted a quartet state as the global minimum.