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|Type:||Artigo de periódico|
|Title:||Enthalpies Of Formation Of Phosphorus And Oxygen Compounds Determined By The Correlation Consistent Composite Approach|
|Abstract:||The heats of formation of small molecules (O 2, O 3, P 2, P 4, PO, PO 2, PO 3, P 2O, P 2O 2, and P 4O 6) have been determined by a modified version of the correlation consistent composite approach (ccCA). The equilibrium geometries and vibrational frequencies were computed via density functional theory, using the M06-2X exchange-correlation functional and 6-31G(2df,p) basis sets. The original methodology requires CCSD(T) energy, which now is obtained by CR-CCSD(T)-L method. The theoretical heats of formation, whose accuracy is estimated as ranging from ±4 to ±10 kJ mol -1, are closer to the available experimental data, but O 3 and P 4O 6 are exceptions, exceed the desired value of ±10 kJ mol -1. The ccCA result for ozone (159.2 kJ mol -1) shows a deviation in comparison to experimental data (142.67 ± 1.7 kJ mol -1), but it is closer to the calculated value 154.0 kJ mol -1 by the high-level quantum chemical calculation (W1U; Janoschek and Fabian, J. Mol. Struct. 2006, 780-781, 80). The value of heat formation to P 4O 6 was estimated to be -1706.3 kJ mol -1. This value is quite different of experimental data, and additional studies are needed to understand this deviation. © 2012 Wiley Periodicals, Inc. Products obtained from reactions between oxygen atoms and phosphorous compounds can be useful for many applications such as laser systems, catalysts, involving ligands in asymmetric metal catalysis, and so forth. So, the acquisition of quantitative characteristics for electronic structure of these compounds is very useful. The thermochemical parameters, such as free energy, heat, and entropy of formation, are the essential properties for the determination of the strength of the chemical bonds associated with these molecular systems. Copyright © 2012 Wiley Periodicals, Inc.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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