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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 (O2, O3, P2, P4, PO, PO2, PO3, P2O, P2O2, and P4O6) 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 O3 and P4O6 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, 780781, 80). The value of heat formation to P4O6 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. (c) 2012 Wiley Periodicals, Inc.|
|Subject:||enthalpies of formation|
phosphorus and oxygen compounds
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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