title: The accuracy of ab initio molecular geometries for systems containing second-row atoms.
abstract: The performance of the standard hierarchy of ab initio models--that is, Hartree-Fock theory, second-order Moller-Plesset theory, coupled-cluster singles-and-doubles theory, and coupled-cluster singles-doubles-approximate-triples theory--in combination with correlation-consistent basis sets is investigated for equilibrium geometries of molecules containing second-row elements. From an analysis on a collection of 31 molecules (yielding statistical samples of 41 bond distances and 13 bond angles), the statistical errors (mean deviation, mean absolute deviation, standard deviation, and maximum absolute deviation) are established at each level of theory. The importance of core correlation is examined by comparing calculations in the frozen-core approximation with calculations where all electrons are correlated.
authors.affiliation: Dipartimento di Scienze Chimiche, Università degli Studi di Trieste, via Licio Giorgieri 1, I-34127 Trieste, Italy. coriani@units.it
authors.forename: Sonia
authors.initials: S
authors.lastname: Coriani
authors.forename: Domenico
authors.initials: D
authors.lastname: Marchesan
authors.forename: Jürgen
authors.initials: J
authors.lastname: Gauss
authors.forename: Christof
authors.initials: C
authors.lastname: Hättig
authors.forename: Trygve
authors.initials: T
authors.lastname: Helgaker
authors.forename: Poul
authors.initials: P
authors.lastname: Jørgensen