{"doi":"10.1021/jp960976r","title":"Harmonic Vibrational Frequencies:  An Evaluation of Hartree−Fock, Møller−Plesset, Quadratic Configuration Interaction, Density Functional Theory, and Semiempirical Scale Factors","abstract":"Scaling factors for obtaining fundamental vibrational frequencies, low-frequency vibrations, zero-point vibrational energies (ZPVE), and thermal contributions to enthalpy and entropy from harmonic frequencies determined at 19 levels of theory have been derived through a least-squares approach. Semiempirical methods (AM1 and PM3), conventional uncorrelated and correlated ab initio molecular orbital procedures [Hartree−Fock (HF), Møller−Plesset (MP2), and quadratic configuration interaction including single and double substitutions (QCISD)], and several variants of density functional theory (DFT: B-LYP, B-P86, B3-LYP, B3-P86, and B3-PW91) have been examined in conjunction with the 3-21G, 6-31G(d), 6-31+G(d), 6-31G(d,p), 6-311G(d,p), and 6-311G(df,p) basis sets. The scaling factors for the theoretical harmonic vibrational frequencies were determined by a comparison with the corresponding experimental fundamentals utilizing a total of 1066 individual vibrations. Scaling factors suitable for low-frequency vibrations were obtained from least-squares fits of inverse frequencies. ZPVE scaling factors were obtained from a comparison of the computed ZPVEs (derived from theoretically determined harmonic vibrational frequencies) with ZPVEs determined from experimental harmonic frequencies and anharmonicity corrections for a set of 39 molecules. Finally, scaling factors for theoretical frequencies that are applicable for the computation of thermal contributions to enthalpy and entropy have been derived. A complete set of recommended scale factors is presented. The most successful procedures overall are B3-PW91/6-31G(d), B3-LYP/6-31G(d), and HF/6-31G(d).","journal":"The Journal of Physical Chemistry","year":1996,"id":5914,"datarank":1.3209186724902677,"base_score":8.80612448326845,"endowment":8.80612448326845,"self_citation_contribution":1.3209186724902677,"citation_network_contribution":0.0,"self_endowment_contribution":1.3209186724902677,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":6674,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.0643,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"1996-01-01","fair_score":55.0,"fair_percentile":80.29903254177661,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":56390,"name":"Leo Radom","orcid":"0000-0001-8249-1314","position":1,"is_corresponding":false},{"id":56389,"name":"Anthony P. 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