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首页> 外文期刊>Spectrochimica acta, Part A. Molecular and biomolecular spectroscopy >Anharmonic analysis of the vibrational spectrum of ketene by density functional theory using second-order perturbative approach
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Anharmonic analysis of the vibrational spectrum of ketene by density functional theory using second-order perturbative approach

机译：用二阶微扰方法通过密度泛函理论分析乙烯酮的振动光谱

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The paper reports main results of a comprehensive study of the vibrational spectrum of ketene computed using second-order perturbation theory treatment based on quartic, cubic and semidiagonal quartic force constants. Two different models-a homogeneous model using the same density functionals and basis functions for the harmonic calculations and anharmonic corrections and a hybrid model in which the two parts of the calculation are conducted using different density functionals and basis sets-have been employed in the present calculations. Different DFT and CCSD methods and DZ and TZ extended basis sets involving diffuse and polarization functions have been used to calculate optimized and vibrationally averaged geometrical parameters, the harmonic and anharmonic vibrational frequencies and the spectroscopic constants such as anharmonicity constants, rotational constants, rotation-vibration coupling constants, Nielsen's centrifugal distortion constants and Coriolis coupling constants. Homogeneous model is found to be superior to the hybrid model in several respects. Difficulties in the hybrid model may arise due to one of the following reasons: (a) the basic: requirement that the geometry optimization and frequency calculations must be done at the same level of theory to have valid frequencies is not met in the hybrid model; (b) the molecular structure gets reoptimized at the low level for anharmonic corrections; (c) in addition, the perturbation could also diverge for the above reasons, particularly for the very low, very anharmonic terms where the harmonic approximation is not close enough. to make the perturbation work. (c) 2006 Published by Elsevier B.V.
机译：本文报告了基于二阶扰动理论处理，基于四次，三次和半对角四次力常数计算的乙烯酮振动谱的综合研究的主要结果。目前，已经采用了两种不同的模型，即使用相同密度函数和基函数进行谐波计算和非谐校正的均质模型，以及使用不同密度函数和基组进行计算的两个部分的混合模型。计算。已使用不同的DFT和CCSD方法以及涉及扩散和偏振函数的DZ和TZ扩展基集来计算优化和振动平均的几何参数，谐波和非谐振动频率以及光谱常数，例如非谐常数，旋转常数，旋转振动耦合常数，尼尔森的离心变形常数和科里奥利耦合常数。发现同质模型在几个方面都优于混合模型。混合模型中的困难可能是由于以下原因之一：（a）基本要求：混合模型中不满足几何学优化和频率计算必须在相同理论水平上进行以具有有效频率的要求; （b）在低水平上重新优化了分子结构以进行非谐校正; （c）此外，由于上述原因，摄动也可能会发散，特别是对于谐波近似不够近的非常低，非常不谐和的项。使摄动工作。 （c）2006年由Elsevier B.V.发布

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