Sequences of basis sets that systematically converge towards the complete basis set (CBS) limit have been developed for the coinage metals (Cu, Ag, Au) and group 12 elements (Zn, Cd, Hg). These basis sets are based on recently published small-core relativistic pseudopotentials [Figgen D, Rauhut G, Dolg M, Stoll H (2005) Chem Phys 311:227] and range in size from double- through quintuple-ζ. Series of basis sets designed for valence-only and outer-core electron correlation are presented, as well as these sets augmented by additional diffuse functions for the accurate description of negative ions and weak interactions. Selected benchmark calculations at the coupled cluster level of theory are presented for both atomic and molecular properties. The latter include the calculation of both spectroscopic and thermochemical properties of the homonuclear dimers Cu2, Ag2, and Au2, as well as the van der Waals species Zn2, Cd2, and Hg2. The CBS limit results, including the effects of core-valence correlation and spin-orbit coupling, represent some of the most accurate carried out to date and result in new recommendations for the equilibrium bond lengths of the group 12 dimers. Comparisons are also made to a limited number of all-electron Douglas–Kroll–Hess (DKH) calculations (second and third order) carried out using new correlation consistent basis sets of triple-ζ quality.

http://tyr0.chem.wsu.edu/~kipeters/pages/pdfs/tca114.283.2005.pdf

Systematically convergent basis sets for transition metals. II. Pseudopotential-based correlation consistent basis sets for the group 11 (Cu, Ag, Au) and 12 (Zn, Cd, Hg) elements

A coupled cluster composite approach has been used to accurately determine the spectroscopic constants, bond dissociation energies, and heats of formation for the X12Π3/2 states of the halogen oxides ClO, BrO, and IO, as well as their negative ions ClO-, BrO-, and IO-. After determining the frozen core, complete basis set (CBS) limit CCSD(T) values, corrections were added for core−valence correlation, relativistic effects (scalar and spin−orbit), the pseudopotential approximation (BrO and IO), iterative connected triple excitations (CCSDT), and iterative quadruples (CCSDTQ). The final ab initio equilibrium bond lengths and harmonic frequencies for ClO and BrO differ from their accurate experimental values by an average of just 0.0005 A and 0.8 cm-1, respectively. The bond length of IO is overestimated by 0.0047 A, presumably due to an underestimation of molecular spin−orbit coupling effects. Spectroscopic constants for the spin−orbit excited X22Π1/2 states are also reported for each species. The predicted...

http://tyr0.chem.wsu.edu/~kipeters/Pages/pdfs/JPC110.13877.2006.pdf

On the spectroscopic and thermochemical properties of ClO, BrO, IO, and their anions.

. During springtime in the polar regions, unique photochemistry converts inert halide salt ions (e.g. Br−) into reactive halogen species (e.g. Br atoms and BrO) that deplete ozone in the boundary layer to near zero levels. Since their discovery in the late 1980s, research on ozone depletion events (ODEs) has made great advances; however many key processes remain poorly understood. In this article we review the history, chemistry, dependence on environmental conditions, and impacts of ODEs. This research has shown the central role of bromine photochemistry, but how salts are transported from the ocean and are oxidized to become reactive halogen species in the air is still not fully understood. Halogens other than bromine (chlorine and iodine) are also activated through incompletely understood mechanisms that are probably coupled to bromine chemistry. The main consequence of halogen activation is chemical destruction of ozone, which removes the primary precursor of atmospheric oxidation, and generation of reactive halogen atoms/oxides that become the primary oxidizing species. The different reactivity of halogens as compared to OH and ozone has broad impacts on atmospheric chemistry, including near complete removal and deposition of mercury, alteration of oxidation fates for organic gases, and export of bromine into the free troposphere. Recent changes in the climate of the Arctic and state of the Arctic sea ice cover are likely to have strong effects on halogen activation and ODEs; however, more research is needed to make meaningful predictions of these changes.

/pdf/halogens-and-their-role-in-polar-boundary-layer-ozone-3v9c7c6k0c.pdf

Halogens and their role in polar boundary-layer ozone depletion

New relativistic energy-consistent pseudopotentials have been generated for the 5d transition metals Hf–Pt. The adjustment was done in numerical two-component multiconfiguration Hartree–Fock calculations, using atomic valence-energy spectra from four-component multiconfiguration Dirac–Hartree–Fock calculations as reference data. The resulting two-component pseudopotentials replace the [Kr]4d104f14 cores of the 5d transition metals and can easily be split into a scalar-relativistic and a spin-orbit part. They reproduce the all-electron reference energy data with deviations of ∼0.01 eV for configurational averages and ∼0.05 eV for individual relativistic states. Full series of correlation consistent basis sets from double to quintuple-zeta have also been developed in this work for use with the new pseudopotentials. In addition, all-electron triple-zeta quality correlation consistent basis sets are also reported in order to provide calibration for the pseudopotential treatment. The accuracy of both the pseud...

Energy-consistent pseudopotentials and correlation consistent basis sets for the 5d elements Hf-Pt.

A review of the theoretical and computational modeling of bimolecular reactions is given. The review is divided into several sections which are as follows: gas-phase thermal reactions; gas-phase state-selected reactions and product state distributions; and condensed-phase bimolecular reactions. The section on gas-phase thermal reactions covers the enthalpies and free energies of reaction, kinetics, saddle points and potential energy surfaces, rate theory for simple barrier reactions and bimolecular reactions over potential wells. The section on gas-phase state-selected reactions focuses on electronically adiabatic reactions and electronically nonadiabatic reactions. Finally, the section on condensed-phase bimolecular reactions covers reactions in liquids, reactions on surfaces and in solids and tunneling at low temperature.

Modeling the Kinetics of Bimolecular Reactions

One of the possible key products in the oxidation and transport of atmospheric mercury is mercury monoxide, HgO. In the present work, large-scale multireference configuration interaction, as well as coupled cluster, wave functions have been used in conjunction with a series of correlation consistent basis sets to calculate the near-equilibrium potential energy functions of the first two electronic states of HgO. In the absence of spin−orbit coupling, the lowest 1Σ+ and 3Π states are nearly isoenergetic with a binding energy with respect to ground-state atoms of only 2−3 kcal/mol at the estimated complete basis set limit. After spin−orbit coupling effects are accurately included, the resulting X0+ state has a D0 of just 4.0 kcal/mol, leading to a ΔHf(0 K) of 70.4 kcal/mol. These values are in stark contrast to the currently accepted experimental values. The implications of these results to atmospheric mercury chemistry are briefly discussed.

http://tyr0.chem.wsu.edu/~kipeters/Pages/pdfs/JPC107.1783.2003.pdf

Mercury Monoxide: A Systematic Investigation of Its Ground Electronic State

A global potential energy surface (PES) for the 1A‘ ground state of HgBr2 has been constructed in order to determine the rate constants for atmospherically important reactions involving mercury and bromine. The total energy of HgBr2 was calculated by the multireference configuration interaction level of theory with series of correlation consistent basis sets up to quadruple-ζ quality with subsequent extrapolation to the complete basis set limit. An additive correction for spin−orbit coupling was also included. The global PES was represented piecewise by interpolating three separate parts of the surface with the reproducing kernel Hilbert space method and connecting them smoothly by switch functions. Quasiclassical trajectory calculations carried out on the surface yielded 298 K thermal rate constants of 3.89 × 10-11 cm3/(mol·s) for the abstraction reaction HgBr + Br → Hg + Br2, 2.98 × 10-11 cm3/(mol·s) for the recombination reaction Br + HgBr → HgBr2, and 3.97 × 10-11 cm3/(mol·s) for the exchange reaction...

http://tyr0.chem.wsu.edu/~kipeters/Pages/pdfs/JPC109.8765.2005.pdf

Accurate Global Potential Energy Surface and Reaction Dynamics for the Ground State of HgBr2

The near-equilibrium potential energy functions of the lowest two electronic states (1Σ+, 3Π) of the group 12 chalcogenides, i.e. {Zn, Cd, Hg} + {O, S, Se, Te, Po}, have been calculated from large-scale multireference configuration interaction (MRCI) and coupled cluster calculations. Use of a sequence of correlation consistent basis sets with accurate relativistic pseudopotentials allowed for the extrapolation of the potential functions to the complete basis set (CBS) limit. Inclusion of spin–orbit coupling yields an avoided crossing between the Ω = 0+ components of the 1Σ+ and 3Π states, which in some cases strongly affects the ground state spectroscopic constants. In almost all cases the calculated ground electronic state corresponds to , except for CdPo, HgSe, HgTe, and HgPo, where the 3Π2 state is calculated to be lowest. Spectroscopic constants and dissociation energies are determined for all states both before and after the inclusion of spin–orbit coupling. Accurate equilibrium dipole moments (witho...

The group 12 metal chalcogenides: an accurate multireference configuration interaction and coupled cluster study

Accurate 0 K enthalpies have been calculated for reactions of mercury with a series of small iodine-containing molecules (I2, IBr, ICl, and IO). The calculations have been carried out with the coupled cluster singles and doubles method with a perturbative correction for connected triple excitations [CCSD(T)] using sequences of correlation consistent basis sets and accurate relativistic pseudopotentials. Corrections have been included to account for core-valence correlation, spin−orbit coupling, scalar relativity, and the Lamb shift. In a few cases coupled cluster calculations with iterative triple (CCSDT) and quadruple (CCSDTQ) excitations have been carried out to estimate the effects of higher order electron correlation. The pseudopotential calculations have also been compared to all electron calculations using second- and third-order Douglas−Kroll−Hess Hamiltonians. In addition to the reaction enthalpies, heats of formation, bond lengths, and harmonic vibrational frequencies have been calculated for the...

http://tyr0.chem.wsu.edu/~kipeters/Pages/pdfs/JPC109.10363.2005.pdf

Benjamin C. Shepler

Papers

On the spectroscopic and thermochemical properties of ClO, BrO, IO, and their anions.

Mercury Monoxide: A Systematic Investigation of Its Ground Electronic State

Accurate Global Potential Energy Surface and Reaction Dynamics for the Ground State of HgBr2

The group 12 metal chalcogenides: an accurate multireference configuration interaction and coupled cluster study

Ab initio thermochemistry involving heavy atoms: an investigation of the reactions Hg + IX (X = I, Br, Cl, O).