title: Generation of potential energy curves for the X1Sigma(+)g, B1Delta(+)g, and B'1Sigma(+)g states of C2 using the effective valence shell Hamiltonian method.
abstract: Calculations of the ground and excited state potential energy curves of C2 using the third-order effective valence Hamiltonian (Hv3rd) method are benchmarked against full configuration interaction and other correlated single-reference perturbative and nonperturbative theories. The large nonparallelity errors (NPEs) exhibited even by state-of-art coupled cluster calculations through perturbative triples indicate a serious deficiency of these single-reference theories. The Hv method, on the other hand, produces a much reduced NPE, rendering it a viable approximate many-body method for accurately determining global ground and excited state potential energy curvessurfaces.
authors.affiliation: Indian Institute of Astrophysics, Bangalore-560034, India. rkchaudh@kff1.uchicago.edu
authors.forename: Rajat K
authors.initials: RK
authors.lastname: Chaudhuri
authors.forename: Karl F
authors.initials: KF
authors.lastname: Freed