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Titolo:
MOLECULAR DENSITY-OF-STATES FROM ESTIMATED VAPOR-PHASE HEAT-CAPACITIES
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:
0538-8066(1997)29:3<161:MDFEVH>2.0.ZU;2-C
Fonte:
ISI
Lingua:
ENG
Soggetto:
SELF-CONSISTENT EQUATIONS; THERMAL UNIMOLECULAR REACTIONS; RATE CONSTANTS; THERMODYNAMIC PROPERTIES; RADICAL REACTIONS; BIMOLECULAR QRRK; COMPUTER CODE; ENTHALPY; ENTROPY; O-2;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
40
Recensione:
Indirizzi per estratti:
Citazione:
J.W. Bozzelli et al., "MOLECULAR DENSITY-OF-STATES FROM ESTIMATED VAPOR-PHASE HEAT-CAPACITIES", International journal of chemical kinetics, 29(3), 1997, pp. 161-170

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 arithmetic-mean 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 H-f(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