title: Surprising quenching of the spin-orbit interaction significantly diminishes H2O···X [X = F, Cl, Br, I] dissociation energies.
abstract: The H2O···X complexes, with X = F, Cl, Br, and I, show considerable viability with nonspin-orbit De(D0) dissociation energy values of 3.73(2.42), 3.60(2.68), 3.54(2.72), and 3.36(2.77) kcal mol(-1) for X = F, Cl, Br, and I, respectively, obtained at the CCSD(T)-F12b/aug-cc-pVTZ(-PP) level of theory using relativistic pseudopotentials (PPs) for Br and I. Spin-orbit (SO) corrections, computed with the Breit-Pauli operator in the interacting states approach at the all-electron MRCI+Q/aug-cc-pwCVTZ(-PP) level, are found to depend sensitively and unpredictably on the O···X separations. 96% (F), 87% (Cl), 54% (Br), and 30% (I) quenching of the SO corrections significantly reduces the dissociation energies of the H2O···X complexes, resulting in De(D0) values of 3.38(2.06), 2.86(1.94), 1.64(0.83), and 1.23(0.64) kcal mol(-1) for X = F, Cl, Br, and I, respectively.
authors.affiliation: Laboratory of Molecular Structure and Dynamics, Institute of Chemistry, Eötvös University , P.O. Box 32, H-1518 Budapest 112, Hungary.
authors.forename: Gábor
authors.initials: G
authors.lastname: Czakó
authors.forename: Attila G
authors.initials: AG
authors.lastname: Császár
authors.forename: Henry F
authors.initials: HF
authors.lastname: Schaefer