Peter Schwerdtfeger

Relativistic effects in gold chemistry. I. Diatomic gold compounds

Nonrelativistic and relativistic Hartree–Fock (HF) and configuration interaction (CI) calculations have been performed in order to analyze the relativistic and correlation effects in various diatomic gold compounds. It is found that relativistic effects reverse the trend in most molecular properties down the group (11). The consequences for gold chemistry are described. Relativistic bond stabilizations or destabilizations are dependent on the electronegativity of the ligand, showing the largest bond destabilization for AuF (86 kJ/mol at the CI level) and the largest stabilization for AuLi (−174 kJ/mol). Relativistic bond contractions lie between 1.09 (AuH+) and 0.16 A (AuF). Relativistic effects of various other properties are discussed. A number of as yet unmeasured spectroscopic properties, such as bondlengths (re), dissociation energies (De), force constants (ke), and dipole moments (μe), are predicted.

The accuracy of the pseudopotential approximation. II. A comparison of various core sizes for indium pseudopotentials in calculations for spectroscopic constants of InH, InF, and InCl

Small‐ and medium‐core pseudopotentials representing [Ar]3d10‐ and [Kr]‐like cores, respectively, have been adjusted for the In atom, supplementing the energy‐consistent three‐valence‐electron large‐core ([Kr]4d10 core) pseudopotential of the Stuttgart group. The performance of these potentials is tested against those of other groups and against experiment, in calculations for the ground‐state potential curves of InH, InF, and InCl, both at the self‐consistent‐field and correlated levels. The role of the core size is discussed, and systematic errors of large‐ and medium‐core pseudopotentials are analyzed.

Accuracy of energy-adjusted quasirelativistic ab initio pseudopotentials: All-electron and pseudopotential benchmark calculations for Hg, HgH and their cations

The results of valence-only self-consistent field calculations on Hg n+ (n = 0, 1, 2) and HgH n+ (n = 0, 1) using nonrelativistic and quasirelativistic energy-adjusted ab initio pseudopotentials for Hg are compared with corresponding all-electron values from nonrelativistic (Hartree-Fock) and relativistic (Dirac-Fock) atomic as well as from nonrelativistic (Hartree-Fock) and quasirelativistic (Hartree-Fock with no-pair Hamiltonian) molecular calculations. The accuracy of the energy-adjusted ab initio pseudopotential scheme, e.g., the reproduction of the major relativistic effects, is demonstrated both for the atom and the molecule. Correlation effects are included in the quasirelativistic pseudopotential studies by means of large-scale configuration interaction calculations. The quasirelativistic pseudopotential results obtained in the intermediate coupling scheme are in excellent agreement with available experimental data.

A systematic search for minimum structures of small gold clusters Aun (n=2–20) and their electronic properties

A systematic search for global and energetically low-lying minimum structures of neutral gold clusters Au(n) (n=2-20) is performed within a seeded genetic algorithm technique using density functional theory together with a relativistic pseudopotential. Choosing the energetically lowest lying structures we obtain electronic properties by applying a larger basis set within an energy-consistent relativistic small-core pseudopotential approach. The possibility of extrapolating these properties to the bulk limit for such small cluster sizes is discussed. In contrast to previous calculations on cesium clusters [B. Assadollahzadeh et al., Phys. Rev. B 78, 245423 (2008)] we find a rather slow convergence of any of the properties toward the bulk limit. As a result, we cannot predict the onset of metallic character with increasing cluster size, and much larger clusters need to be considered to obtain any useful information about the bulk limit. Our calculated properties show a large odd-even cluster size oscillation in agreement, for example, with experimental ionization potentials and electron affinities. For the calculated polarizabilities we find a clear transition to lower values at Au14, the first cluster size where the predicted global minimum clearly shows a compact three-dimensional (3D) structure. Hence, the measurement of cluster polarizabilities is ideal to identify the 2D-->3D transition at low temperatures for gold. Our genetic algorithm confirms the pyramidal structure for Au20.

Metallophilic Interactions in Closed-Shell Copper(I) Compounds—A Theoretical Study

Cuprophilic interactions in neutral perpendicular model dimers of the type (CH3CuX)2 (X = OH2, NH3, SH2, PH3, N2, CO, CS, CNH, CNLi) were analyzed by ab initio quantumchemical methods. The basis set superposition error for the weakly interacting CH3CuX subunits is significant and is discussed in detail. A new correlation-consistent pseudopotential valence basis set for Cu. derived at the second-order Møller-Plesset level suppresses considerably the basis set superposition error in Cu-Cu interactions compared to the standard Hartree-Fock optimized valence basis set. This allowed the first accurate predictions of cuprophilicity, which has been the subject of considerable debate in the past. The dependence of the strength of cuprophilic interactions on the nature of the ligand X was addressed. The Cu-Cu interaction increases with increasing sigma-donor and pi-acceptor capability of the ligand and is approximately one-third of the well-documented aurophilic interactions. By fitting our potential-energy data to the Hershbach-Laurie equation, we determined a relation between the Cu-Cu bond length and the Cu-Cu force constant; this is important for future studies on vibrational behaviour. The role of relativistic effects on the structure and the interaction energy is also discussed. Finally we investigated cuprophilic interactions in (CH3Cu)4 as a model species for compounds isolated and characterized by X-ray diffraction.

All-electron and relativistic pseudopotential studies for the group 1 element polarizabilities from K to element 119

Two-component and scalar relativistic energy-consistent pseudopotentials for the group 1 elements from K to element 119 are presented using nine electrons for the valence space definition. The accuracy of such an approximation is discussed for dipole polarizabilities and ionization potentials obtained at the coupled-cluster level as compared to experimental and all-electron Douglas-Kroll results.

Relativistic atomic orbital contractions and expansions: magnitudes and explanations

The magnitude of the relativistic contraction or expansion of atomic orbitals is usually obtained by a comparison of the expectation values of r in a Dirac-Fock calculation and in a Hartree-Fock calculation. As, however, the Dirac Hamiltonian is implicitly given in a different picture from the non-relativistic Schrodinger Hamiltonian, the operator r does not correspond to the same physical quantity in the two cases. A proper definition of relativistic AO contraction/expansion should use the same physical quantity in both the relativistic and non-relativistic cases; for instance experiments with photons measure matrix elements of Pcharger which is represented by the operator r in the Dirac picture and by U,,rU&, in the Schrodinger picture ( U,, is the Foldy-Wouthuysen transformation). Accordingly, the conventional values of the relativistic AO contraction consist of two contributions. One is due to the relativistic modification of the orbital; the other one is due to the different meanings of r in the Schrodinger and Dirac pictures. This latter difference turns out to be significant for Is AO, where it is 50%. The large relativistic contraction of valence s AO of heavy elements is investigated. Using perturbation theory or the resolution of the identity into projection operators, the orthogonality of the valence AO on the strongly contracted inner core orbitals is shown to have a slight valence-expanding effect, while mixing in of the higher continuum orbitals by the relativistic correction of the Hamiltonian is responsible for the overall contraction.

Homogeneous Gold Catalysis: Mechanism and Relativistic Effects of the Addition of Water to Propyne

Homogeneous catalysis employing gold compounds is a rapidly developing field. Au(III) catalysts in particular are interesting, since they exhibit catalytic properties unseen in other metals. In this study we report for the first time the complete mechanism of the nucleophilic addition of water to triple bonds that have not specifically been activated. The effect that the coordination of solvent molecules has on the course of the catalytic cycle is demonstrated, and the importance of hydrogen bonds to guide the substrate through the mechanism is highlighted. The influence of relativistic effects, which are particularly important for very heavy metals such as gold, is investigated, and it is concluded that the catalytic activity of gold could be seen as a relativistic effect.

The chemistry of the superheavy elements. I. Pseudopotentials for 111 and 112 and relativistic coupled cluster calculations for (112)H+, (112)F2, and (112)F4

One- and two-component (spin–orbit coupled) relativistic and nonrelativistic energy adjusted pseudopotentials and basis sets for the elements 111 and 112 are presented. Calculations on the positively charged monohydride of the recently discovered superheavy element 112 are reported. Electron correlation is treated at the multireference configuration interaction and coupled cluster level and fine structure effects are derived from a single-reference configuration interaction treatment. Relativistic effects decrease the (112)H+ bond distance by 0.41 A. This bond contraction is similar to the one calculated recently for (111)H [Chem. Phys. Lett. 250, 461 (1996)]. As a result the bond distance of (112)H+ (1.52 A) is predicted to be smaller compared to those of the hydrides of the lighter congeners HgH+ (1.59 A), CdH+ (1.60 A) and similar to that of ZnH+ (1.52 A). We predict that (112)H+ is the most stable hydride in the Group 12 series due to relativistic effects. As in the case of (111)H the relativistic inc...

Relativistic coupled cluster calculations for neutral and singly charged Au3 clusters

Relativistic coupled cluster studies are performed for the structures, dissociation energies, ionization potentials and electron affinities for Au, Au2 and Au3. The calculations show that the upward shifts of the ionization potentials and electron affinities of Aun clusters by approximately 2 eV compared to Cun or Agn base on relativistic effects. Au3+ is predicted to adopt a trigonal planar structure (D3h, 1A1), Au3 a E⊗e Jahn–Teller distorted structure (C2v,2A1) 0.1 eV below the linear 2Σu+ arrangement, and Au3− adopts a linear structure (1Σg+).