Ab initio effective core potentials (ECP’s) have been generated to replace the Coulomb, exchange, and core‐orthogonality effects of the chemically inert core electron in the transition metal atoms Sc to Hg. For the second and third transition series relative ECP’s have been generated which also incorporate the mass–velocity and Darwin relativistic effects into the potential. The ab initio ECP’s should facilitate valence electron calculations on molecules containing transition‐metal atoms with accuracies approaching all‐electron calculations at a fraction of the computational cost. Analytic fits to the potentials are presented for use in multicenter integral evaluation. Gaussian orbital valence basis sets are developed for the (3d,4s,4p), (4d,5s,5p), and (5d,6s,6p) orbitals of the first, second, and third transition series atoms, respectively. All‐electron and valence‐electron atomic excitation energies are also compared for the low‐lying states of Sc–Hg, and the valence‐electron calculations are found to reproduce the all‐electron excitation energies (typically within a few tenths of an eV).

Ab initio effective core potentials for molecular calculations. Potentials for the transition metal atoms Sc to Hg

Nitrogen (N)-doped carbon materials exhibit high electrocatalytic activity for the oxygen reduction reaction (ORR), which is essential for several renewable energy systems. However, the ORR active site (or sites) is unclear, which retards further developments of high-performance catalysts. Here, we characterized the ORR active site by using newly designed graphite (highly oriented pyrolitic graphite) model catalysts with well-defined π conjugation and well-controlled doping of N species. The ORR active site is created by pyridinic N. Carbon dioxide adsorption experiments indicated that pyridinic N also creates Lewis basic sites. The specific activities per pyridinic N in the HOPG model catalysts are comparable with those of N-doped graphene powder catalysts. Thus, the ORR active sites in N-doped carbon materials are carbon atoms with Lewis basicity next to pyridinic N.

Active sites of nitrogen-doped carbon materials for oxygen reduction reaction clarified using model catalysts

Today, coupled-cluster theory offers the most accurate results among the practical ab initio electronic-structure theories applicable to moderate-sized molecules. Though it was originally proposed for problems in physics, it has seen its greatest development in chemistry, enabling an extensive range of applications to molecular structure, excited states, properties, and all kinds of spectroscopy. In this review, the essential aspects of the theory are explained and illustrated with informative numerical results.

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Coupled-cluster theory in quantum chemistry

Physical Review B

https://courses.washington.edu/cfr523/documents/Alonso2010CatalyticConversion.pdf

Catalytic conversion of biomass to biofuels

Direct molecular dynamics and density-functional theoretical study of the electrochemical hydrogen oxidation reaction and underpotential deposition of H on Pt(111)

The electronic level structure of eka-lead (element 114), the synthesis of which was reported last year, is studied by the recently developed intermediate Hamiltonian Fock-space coupled-cluster method. Very large basis sets are used, with l up to 8, and 36 electron are correlated. The accuracy of the resulting transition energies is tested by applying the same method to Pb; calculated ionization potentials and excitation energies agree with experiment within a few hundredths of an eV, and similar accuracy is expected for the heavier element. Ionization potentials and excitation energies of E114 are considerably higher than for Pb, due to the relativistic stabilization of the 7s and 7p1/2 orbitals. This indicates that eka-lead will probably be more inert and less metallic than lead.

Electronic structure of eka-lead (element 114) compared with lead

The self-consistent-field treatment of the frequency-independent Breit interaction is reviewed with applications to many-electron atoms. The implementation of the matrix Dirac-Fock-Breit self-consistent-field procedure is presented for Gaussian-type basis sets that show no near-linear dependency problem. The matrix Dirac-Fock-Breit procedure has the advantage over the finite-difference approach that it does not complicate the self-consistent-field procedure in basis-set expansion calculations. Basis sets of even- and well-tempered Gaussian functions were used to expand the large and small components of Dirac four-spinors. Expressions are derived for evaluating the matrix elements of the Dirac-Fock-Breit equations. Calculations done on rare-gas atoms He, Ne, Ar, Kr, and Xe and alkaline-earth metals Be, Mg, Ca, and Sr are presented.

Dirac-Fock-Breit self-consistent-field method: Gaussian basis-set calculations on many-electron atoms

A relativistic multireference many-body perturbation theory for quasidegenerate systems with multiple open valence shells is developed and implemented with analytic basis sets of Gaussian spinors. The theory employs a general class of multiconfigurational Dirac-Fock self-consistent-field wave functions as reference functions, and thus is applicable to open-shell systems with near degeneracy of a manifold of strongly interacting configurations. A procedure is described by which to perform multireference second-order M\o{}ller-Plesset perturbation calculations for a general class of reference functions constructed from one-particle Dirac spinors. Multireference perturbation calculations are reported for the ground and low-lying excited states of oxygen and oxygenlike ions with up to a nuclear charge of $Z=60$ in which the near degeneracy of a manifold of strongly interacting configurations mandates a multireference treatment.

Relativistic multireference many-body perturbation theory for quasidegenerate systems: Energy levels of ions of the oxygen isoelectronic sequence

A new four-component Dirac–Kohn–Sham (DKS) method is presented. The method provides a computationally efficient way to perform fully relativistic and correlated ground state calculations on heavy-atom molecular systems with reliable accuracy. The DKS routine has been implemented in the four-component Dirac–Hartree–Fock program system REL4D. Two-component generally contracted, kinetically balanced Gaussian-type spinors (GTSs) are used as basis spinors. The one-electron and Coulomb integrals are computed analytically, and exchange-correlation potentials are calculated with a numerical grid-quadrature routine. An approximation scheme is presented to reduce the evaluation time of the two-electron repulsion integrals over full sets of small-component GTSs, (SS|SS). Benchmark calculations for the ground states of the group IB hydrides, MH, and dimers, M2 (M=Cu, Ag, and Au), by the DKS method are presented.

Yasuyuki Ishikawa

Papers

Direct molecular dynamics and density-functional theoretical study of the electrochemical hydrogen oxidation reaction and underpotential deposition of H on Pt(111)

Electronic structure of eka-lead (element 114) compared with lead

Dirac-Fock-Breit self-consistent-field method: Gaussian basis-set calculations on many-electron atoms

Relativistic multireference many-body perturbation theory for quasidegenerate systems: Energy levels of ions of the oxygen isoelectronic sequence

A new implementation of four-component relativistic density functional method for heavy-atom polyatomic systems