Uncertainties in scaling factors for ab initio vibrational frequencies
Uncertainties in scaling factors for ab initio vibrational frequencies
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DOI：
10.1021/jp052793n
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发表时间：
2005-09-22
影响因子：
2.9
通讯作者：
Kacker, RN
中科院分区：
文献类型：
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作者：
Irikura, KK;Johnson, RD;Kacker, RN
由从头算确定的振动频率通常由经验因子决定。经验标度因子部分补偿了振动非谐性和对电子关联的不完全处理所产生的误差。这些错误不是随机的，而是系统性的偏差。我们报告了40种理论和基组组合的比例因子，用于从计算的简谐频率预测基频。经验比例系数带有不确定性。我们首次量化并报告了与比例因子相关的不确定性。不确定因素比人们普遍承认的要大；比例系数只有两位数。例如，HF/6-31G(D)的比例因数为0.8982+/-0.0230(标准不确定度)。标度因子中的不确定性导致了预测振动频率的相应不确定性。对与比例因数相关的不确定度进行量化的拟议方法是基于国际标准化组织(ISO)出版的《测量不确定度表示指南》。使用的数据来自计算化学比较和基准数据库(CCCBDB)，该数据库由美国国家标准与技术研究所维护，其中包括358个分子的3939个独立振动。
Vibrational frequencies determined from ab initio calculations are often scaled by empirical factors. An empirical scaling factor partially compensates for the errors arising from vibrational anharmonicity and incomplete treatment of electron correlation. These errors are not random but are systematic biases. We report scaling factors for 40 combinations of theory and basis set, intended for predicting the fundamental frequencies from computed harmonic frequencies. An empirical scaling factor carries uncertainty. We quantify and report, for the first time, the uncertainties associated with the scaling factors. The uncertainties are larger than generally acknowledged; the scaling factors have only two significant digits. For example, the scaling factor for HF/6-31G(d) is 0.8982 +/- 0.0230 (standard uncertainty). The uncertainties in the scaling factors lead to corresponding uncertainties in predicted vibrational frequencies. The proposed method for quantifying the uncertainties associated with scaling factors is based on the Guide to the Expression of Uncertainty in Measurement, published by the International Organization for Standardization (ISO). The data used are from the Computational Chemistry Comparison and Benchmark Database (CCCBDB), maintained by the National Institute of Standards and Technology, which includes more than 3939 independent vibrations for 358 molecules.