Structures and stabilities of MgC3 isomers: a theoretical study

A theoretical study of the MgC3 species has been carried out. There are fou r species lying within 2 kcal/mol and that could be accessible to experimen tal detection: two open-chain structures, 1s((1)A') and 1s((3)Pi), and two rhombic four-membered rings, 3s((1)A(1)) and 3t((3)A(1)). The rhombic singl et species seems to be the best candidate for the global minimum, though th e corresponding triplet is nearly isoenergetic. Our conclusion is in contra st with a previous theoretical study on this system that predicted a three- membered ring species as the global minimum. (C) 2001 Elsevier Science B.V. All rights reserved.