Anharmonic vibrational frequencies and vibrationally-averaged structures of key species in hydrocarbon combustion: HCO , HCO, HNO, HOO, HOO-, CH3 , and CH3

作者：Keceli Murat; Shiozaki Toru; Yagi Kiyoshi; Hirata So^*

来源：Molecular Physics, 2009, 107(8-12): 1283-1301.

DOI：10.1080/00268970902889626

• molecular vibrations
• anharmonicity
• potential energy surfaces
• electron correlation
• hydrocarbon combustion

A general scheme to predict anharmonic vibrational frequencies and vibrationally-averaged structures and rotational constants of molecules is presented with applications to some key species in hydrocarbon combustion (some also of importance in atmospheric and/or interstellar chemistry): HCO , HCO, HNO, HOO, HOO-, CH3 , and CH3. A combination of coupled-cluster singles and doubles (CCSD), CCSD with a second-order perturbation correction in the space of triples [CCSD(2)(T)] and in the space of triples and quadruples [CCSD(2)(TQ)], and a correlation-consistent basis set series has been employed to achieve the complete-correlation, complete-basis-set limits of the potential energy surfaces (PESs) of these species near equilibrium geometries. A new, compact representation of PESs that combines two existing representations, namely, a fourth-order Taylor expansion and numerical values on a rectilinear grid, has been proposed and shown to yield accurate frequencies, when combined with vibrational general-order configuration-interaction method. The predicted frequencies (and the observed in parentheses, when available) of the fundamentals are as follows: 823 (830), 2175 ( 2184), and 3083 (3089) cm(-1) in HCO ; 1079 (1081), 1874 (1868), 2432 ( 2434) cm(-1) in HCO; 1503 (1501), 1572 ( 1565), and 2683 (2684) cm(-1) in HNO; 1121 (1098), 1399 (1392), and 3447 ( 3436) cm(-1) in HOO; 739, 1088, and 3587 cm(-1) in HOO-; 1383 (1359 /- 7), 1384 (1370 /- 7), 2940, and 3096 (3108) cm(-1) in CH3 ; 565 (606), 1377, 3002 (3004), and 3139 (3161) cm(-1) in CH3. The mean absolute deviation in the predicted frequencies is 11 cm(-1)

• 出版日期2009