Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
SETI Institute, 189 Bernardo Ave, Suite 100, Mountain View, California 94043, USA.
J Chem Phys. 2013 Dec 14;139(22):224302. doi: 10.1063/1.4837177.
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.
我们报告了一个 CCSD(T)/cc-pCV5Z 四次力场 (QFF) 和一个半全局 CCSD(T)-F12b/aug-cc-pVTZ 位能面 (PES) 用于单重态、环状 C4。使用振动二级微扰理论 (VPT2) 和振动组态相互作用 (VCI) 方法获得了振动基频、组合和泛频。使用 MULTIMODE (MM) 程序，在 QFF 和 PES 上使用 VCI 计算的基本振动与 VPT2 的结果之间的一致性在 10 cm(-1) 以内，并且对于基本振动，VPT2 和 VCI 的结果是一致的。VPT2-QFF 和 MM-QFF 结果之间对于 C4 组合和泛频的一致性也很好。报告了来自 PES 上的 VCI (MM) 和 QFF 计算上的 VPT2 的 J = 1 和 J = 2 转动振动能量。给出了 (12)C4 和两个 C2v 对称、单 (13)C 取代的同位素的光谱常数，这可能有助于在未来的实验分析或天文观测中识别环状 C4。
