title: Anharmonic rovibrational calculations of singlet cyclic C4 using a new ab initio potential and a quartic force field.
abstract: We report a CCSD(T)/cc-pCV5Z quartic force field (QFF) and a semi-global CCSD(T)-F12b/aug-cc-pVTZ potential energy surface (PES) for singlet, cyclic C4. Vibrational fundamentals, combinations, and overtones are obtained using vibrational second-order perturbation theory (VPT2) and the vibrational configuration-interaction (VCI) approach. Agreement is within 10 cm(-1) between the VCI calculated fundamentals on the QFF and PES using the MULTIMODE (MM) program, and VPT2 and VCI results agree for the fundamentals. The agreement between VPT2-QFF and MM-QFF results is also good for the C4 combinations and overtones. The J = 1 and J = 2 rovibrational energies are reported from both VCI (MM) on the PES and VPT2 on the QFF calculations. The spectroscopic constants of (12)C4 and two C2v-symmetry, single (13)C-substituted isotopologues are presented, which may help identification of cyclic C4 in future experimental analyses or astronomical observations.
authors: Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
authors: Xiaohong
authors: X
authors: Wang
authors: SETI Institute, 189 Bernardo Ave, Suite 100, Mountain View, California 94043, USA.
authors: Xinchuan
authors: X
authors: Huang
authors: Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
authors: Joel M
authors: JM
authors: Bowman
authors: MS 245-1, NASA Ames Research Center, Mofffett Field, California 94035, USA.
authors: Timothy J
authors: TJ
authors: Lee