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Titolo: MOLECULAR DENSITYOFSTATES FROM ESTIMATED VAPORPHASE HEATCAPACITIES
Autore: BOZZELLI JW; CHANG AY; DEAN AM;
 Indirizzi:
 NEW JERSEY INST TECHNOL NEWARK NJ 07102 EXXON RES & ENGN CO,CORP RES LABS ANNANDALE NJ 08801
 Titolo Testata:
 International journal of chemical kinetics
fascicolo: 3,
volume: 29,
anno: 1997,
pagine: 161  170
 SICI:
 05388066(1997)29:3<161:MDFEVH>2.0.ZU;2C
 Fonte:
 ISI
 Lingua:
 ENG
 Soggetto:
 SELFCONSISTENT EQUATIONS; THERMAL UNIMOLECULAR REACTIONS; RATE CONSTANTS; THERMODYNAMIC PROPERTIES; RADICAL REACTIONS; BIMOLECULAR QRRK; COMPUTER CODE; ENTHALPY; ENTROPY; O2;
 Tipo documento:
 Article
 Natura:
 Periodico
 Settore Disciplinare:
 Science Citation Index Expanded
 Citazioni:
 40
 Recensione:
 Indirizzi per estratti:



 Citazione:
 J.W. Bozzelli et al., "MOLECULAR DENSITYOFSTATES FROM ESTIMATED VAPORPHASE HEATCAPACITIES", International journal of chemical kinetics, 29(3), 1997, pp. 161170
Abstract
Heat capacity data between 298 and 1500K are used to derive a reducedset of apparent vibrational frequencies that can be used for estimation of molecular density of states, rho(E). Estimates for a number of molecule and radical species, using a reduced set of three frequencies with noninteger degeneracies, are shown to compare favorably to directcount methods, which require specification of the complete frequency set. Use of the reduced set of three frequencies leads to significant improvement in calculations of rho(E)/Q as compared to similar calculations which use only a single geometric or arithmeticmean frequency approximation. Since vapor phase heat capacity data of molecules and radicals can be estimated accurately by a group additivity formalism, this approach provides a method to estimate rho(E) for use in calculations of pressure effects in unimolecular and chemical activation reaction systems. The accuracy of the rho(E)/Q distributions obtained from heat capacity data makes this a viable method for those cases where thecomplete frequency distribution is not known. It is especially valuable for those cases where contributions to rho(E) from internal rotors or low frequency vibrations such as inversions are not well known. This approach is useful for quantum RRK or inverse Laplace transform calculations of k(E) since no assignment of transition state properties isnecessary. The reduced frequency set can also be combined with Delta Hf(298) and S(298) to provide a compact data set to describe thermodynamic properties at any temperature. (C) 1997 John Wiley & Sons, Inc.
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Documento generato il 24/10/20 alle ore 11:09:56