title: Do non-centro-symmetric linear X-Y-X molecules exist? The case for the (I)2Pi(u) state of CuCl2.
abstract: The potential energy surface of the low-lying excited state (I)(2)Pi(u) of CuCl(2) is constructed by using the ionization potential equation-of-motion coupled-cluster method and also the RASPT2 method with a large active space of 21 electrons in 17 orbitals to improve the results. It is found by the multiconfiguration calculation that this state has a barrier of 53 cm(-1) between two equivalent minima in which the linear molecule has a dipole moment. In our computations artifactual symmetry breaking is carefully avoided. Further refinement, including consideration of interaction between the two excited (2)Pi states, yields a somewhat higher barrier between 100 and 500 cm(-1). The mechanism of formation of the double-minimum potential is explained by the pseudo-Jahn-Teller effect theory. Computed spectroscopic constants are in good agreement with experimental ones.
authors.affiliation: Institute for Theoretical Chemistry, Chemistry and Biochemistry Department, The University of Texas at Austin, Austin, Texas 78712-0165, USA.
authors.forename: Wenli
authors.initials: W
authors.lastname: Zou
authors.forename: Isaac B
authors.initials: IB
authors.lastname: Bersuker
authors.forename: James E
authors.initials: JE
authors.lastname: Boggs