Highly accurate potential-energy and dipole moment surfaces for vibrational state calculations of methane - art. no. 064311

作     者：Oyanagi, C Yagi, K Taketsugu, T Hirao, K 

作者机构：Ochanomizu Univ Dept Chem Bunkyo Ku Tokyo 1128610 Japan Univ Tokyo Sch Engn Dept Appl Chem Tokyo 1138656 Japan Hokkaido Univ Grad Sch Sci Div Chem Sapporo Hokkaido 0600810 Japan 

出 版 物：《JOURNAL OF CHEMICAL PHYSICS》 (化学物理学杂志)

年 卷 期：2006年第124卷第6期

页      面：64311-1-64311-页

核心收录：

学科分类：081704[工学-应用化学] 07[理学] 070304[理学-物理化学(含∶化学物理)] 08[工学] 0817[工学-化学工程与技术] 0703[理学-化学] 0702[理学-物理学] 

基　　金：Ministry of Education  Science and Culture  and Sports 

主　　题：SELF-CONSISTENT-FIELD QUARTIC FORCE-FIELD CLASSICAL TRAJECTORYCALCULATIONS DOUBLE-RESONANCE OBSERVATION PERTURBATION-THEORY VARIATIONAL CALCULATIONS ROVIBRATIONAL ENERGIES DYNAMICS CALCULATIONS ANHARMONIC COUPLINGS POLYATOMIC-MOLECULES 

摘      要：Full-dimensional ab initio potential-energy surface (PES) and dipole moment surface are constructed for a methane molecule at the CCSD(T)/cc-pVTZ and MP2/cc-pVTZ levels of theory, respectively, by the modified Shepard interpolation method based on the fourth-order Taylor expansion [MSI(4th)]. The reference points for the interpolation have been set in the coupling region of CH symmetric and antisymmetric stretching modes so as to reproduce the vibrational energy levels related to CH stretching vibrations. The vibrational configuration-interaction calculations have been performed to obtain the energy levels and the absorption intensities up to 9000 cm(-1) with the use of MSI(4th)-PES. The calculated fundamental frequencies and low-lying vibrational energy levels show that MSI(4th) is superior to the widely employed quartic force field, giving a better agreement with the experimental values. The absorption bands of overtones as well as combination bands, which are caused by purely anharmonic effects, have been obtained up to 9000 cm(-1). Strongly coupled states with visible intensity have been found in the 6500-9000 cm(-1) region where the experimental data are still lacking.