title: G4CEP: A G4 theory modification by including pseudopotential for molecules containing first-, second- and third-row representative elements.
abstract: The G4CEP composite method was developed from the respective G4 all-electron version by considering the implementation of compact effective pseudopotential (CEP). The G3/05 test set was used as reference to benchmark the adaptation by treating in this work atoms and compounds from the first and second periods of the periodic table, as well as representative elements of the third period, comprising 440 thermochemical data. G4CEP has not reached a so high level of accuracy as the G4 all-electron theory. G4CEP presented a mean absolute error around 1.09 kcal mol(-1), while the original method presents a deviation corresponding to 0.83 kcal mol(-1). The similarity of the optimized molecular geometries between G4 and G4CEP indicates that the core-electron effects and basis set adjustments may be pointed out as a significant factor responsible for the large discrepancies between the pseudopotential results and the experimental data, or even that the all-electron calculations are more efficient either in its formulation or in the cancellation of errors. When the G4CEP mean absolute error (1.09 kcal mol(-1)) is compared to 1.29 kcal mol(-1) from G3CEP, it does not seem so efficient. However, while the G3CEP uncertainty is ±4.06 kcal mol(-1), the G4CEP deviation is ±2.72 kcal mol(-1). Therefore, the G4CEP theory is considerably more reliable than any previous combination of composite theory and pseudopotential, particularly for enthalpies of formation and electron affinities.
authors.affiliation: Instituto de Química, Universidade Estadual de Campinas, Barão Geraldo, P.O. Box 6154, 13083-970 Campinas, São Paulo, Brazil.
authors.forename: Cleuton de Souza
authors.initials: Cde S
authors.lastname: Silva
authors.affiliation: Departamento de Ciências Exatas e Biotecnológicas, Universidade Federal do Tocantins, Campus de Gurupi, 77410-530 Gurupi, Tocantins, Brazil.
authors.forename: Douglas Henrique
authors.initials: DH
authors.lastname: Pereira
authors.affiliation: Instituto de Química, Universidade Estadual de Campinas, Barão Geraldo, P.O. Box 6154, 13083-970 Campinas, São Paulo, Brazil.
authors.forename: Rogério
authors.initials: R
authors.lastname: Custodio