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Theoretical quantum chemical study of benzoic acid£ºgeometrical para meters and vibrational wavenumbers. Palafox , M.Alcolea;Nunez,J.L.;Gil,M.(departamento de quimica Fisica I,Facultad de ciencias Quimicas,Vniversidad Complutense,Madrid£¬Spanish 28040-ES).international Journal of Quantum Chemistry 2002,89(1),1-24(Eng),John Wiley & Sons,Inc. The structure of benzoic acid as monomer was studied by semiempirical,abinitio,and d. functional methods using several basis sets. The performance of these methods in calcg. and describing the vibrational frequencies of benzoic acid and several derivs. was detd. The cyclic dimer form of benzoic acid was also reproduced. Two new procedures of scaling the frequencies were presented. For the ring modes, specific scale equations and scale factors were used from benzoic mol. For the carboxylic group, scaling equations and specific scale factors at different levels were also detd. To be used in benzoic acid derivs. A reassignment of several bands was done. A comparison of the cost/effective method and procedure of scaling was carried out. A significant redn. Of the error in the predicted frequencies was obtained over the one-factor std. scaling produce. £¨×Ô¼º´ò³öÀ´µÄ£¬¿ÉÒÔ»áÓÐһЩµØ·½ÓÐÎó~~£© °ÝÍи÷λ~~~ |
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Properties, Dynamics, and Electronic Structure of Atoms and Molecules Theoretical quantum chemical study of benzoic acid: Geometrical parameters and vibrational wavenumbers M. Alcolea Palafox *, J. L. N¨²ñez, M. Gil Departamento de Qu¨ªmica F¨ªsica I, Facultad de Ciencias Qu¨ªmicas, Universidad Complutense, Madrid 28040-ES, Spain email: M. Alcolea Palafox (alcolea@quim.ucm.es) *Correspondence to M. Alcolea Palafox, Departamento de Qu¨ªmica F¨ªsica I, Facultad de Ciencias Qu¨ªmicas, Universidad Complutense, Madrid 28040-ES, Spain Keywords benzoic acid • scaling • ab initio methods • vibrational frequencies Abstract The structure of benzoic acid as monomer was studied by semiempirical, ab initio, and density functional methods using several basis sets. The performance of these methods in calculating and describing the vibrational frequencies of benzoic acid and several derivatives was determined. The cyclic dimer form of benzoic acid was also reproduced. Two new procedures of scaling the frequencies were presented. For the ring modes, specific scale equations and scale factors were used from benzene molecule. For the carboxylic group, scaling equations and specific scale factors at different levels were also determined to be used in benzoic acid derivatives. A reassignment of several bands was done. A comparison of the cost/effective method and procedure of scaling was carried out. A significant reduction of the error in the predicted frequencies was obtained over the one-factor standard scaling procedure. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 -------------------------------------------------------------------------------- Received: 12 September 2001; Revised: 11 February 2002; Accepted: 13 February 2002 Digital Object Identifier (DOI) 10.1002/qua.10202 About DOI |

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