Cu and Ag as one‐valence‐electron atoms: CI results and quadrupole corrections for Cu2, Ag2, CuH, and AgH

Relativistic energy-consistent pseudopotentials--recent developments

The direct adjustment of two-component pseudopotentials (scalar-relativistic + spin-orbit potentials), to atomic total energy valence spectra derived from four-component multiconfiguration Dirac-Hartree-Fock all-electron calculations based on the Dirac-Coulomb-Breit Hamiltonian, has been made a routine tool for an efficient treatment of heavy main-group elements. Both large-core (nsp valence shell) and small-core ((n - 1)spd nsp valence shell) potentials have been generated for all the post-d elements of groups 13-17. At the example of lead and bismuth compounds (PbHal, BiH, BiO, BiHal (Hal = F, Cl, Br, I)), we show how small-core and large-core potentials can be combined in accurate, yet computationally economic, spin-free-state-shifted relativistic electronic structure calculations of molecular ground and excited states.

Understanding parity violation in molecular systems

Parity-violation energy (E(PV)) due to weak nuclear interactions between nucleons and electrons in chiral molecular systems provides a fundamental tool to verify our understanding of electronic behavior in complex systems. We used both a relativistic and a nonrelativistic approach to study a number of simple molecules and analyze the corresponding E(PV) in terms of intuitive electrodynamic concepts. We developed a qualitative model to predict the sign of E(PV) and its behavior against selected geometric distortions. Our model provides a valuable tool to screen large sets of molecules and select interesting candidates for more expensive investigations.

Relativistic pseudopotentional incorporating core/valence polarization and nonlocal effects

A relativistic pseudopotentional (RPP) for use in ab initio molecular electronic structure calculations is derived in the context of the relativistic effective core potential (REP) method of Lee et al. The resulting atom-specific RPP has salient features of the REP imbedded within it while retaining the form of a functional that is dynamically defined at runtime when used in calculations on molecules. The RPP is determined from Dirac-Fock wave functions for the isolated atom. Outer core two-electron interactions are incorporated into the RPP by means of variable coefficients that are defined in the context of the final molecular wave function. This form permits polarization of the outer core shells analogous to that occurring in all-electron molecular Hartree-Fock calculations while retaining these shells as part of the atomic pseudopotentional. Use of the RPP in post-Hartree-Fock molecular calculations permits the incorporation of core/valence correlation effects.

Nodeless valence (pseudo)spinors

Atomic calculations using small-core relativistic effective core potentials (RECPs) explicitly treating outer core electrons are used to define two-component nodeless valence spinors (NVSs) and nodeless valence pseudospinors (NVPSs). Errors attributable to nonlocal electron repulsion interactions that arise from large-core RECPs are shown to result from the inherent arbitrariness in the choice of match points and number of derivatives that define shape-consistent pseudospinors, as well as the positions of radial nodes that reside in the outer core regions of atoms. Self-consistent field calculations in omegaomega-coupling for InH and InCl using RECPs derived from NVSs and NVPSs are reported. Increased bond distances relative to those calculated using very-large-core RECPs for In agree with those due to frozen 4d(3/2) and 4d(5/2) spinors and a small-core RECP. Results for AmCl+2 also reveal that the shortening in the bond length is recovered when the very-large-core RECP is derived using nodeless valence (pseudo)spinors.