Theoretical study of AlC3: linear or cyclic ground state?

A theoretical study of the AlC3 species has been carried out. There are thr ee species that lie quite close in energy: a rhombic four-membered ring, 1( (2)A(1)), a T-shape structure, 2(B-2(2)), and a linear species, 3((II)-I-2) . The linear isomer is predicted to be lower in energy, but 1((2)A(1)) lies only about 1-2 kcal mol(-1) higher. In any case, it seems that both isomer s could be accesible to experimental detection. Our conclusion is in contra st with a previous theoretical study on this system that predicted a quarte t state as the global minimum. (C) 2000 Elsevier Science B.V. All rights re served.