A. Zaitsevskii

Multi-partitioning Møller-Plesset perturbation theory. A state-selective formulation

Abstract A state-selective (intermediate Hamiltonian) formulation of the recently proposed multi-partitioning Moller-Plesset perturbation theory is presented. The novel approach offers the possibility to combine the decontracted treatment of the reference space parts of wavefunctions with numerical stability in the presence of intruder states and strict separability at second order. Test applications to molecular electronic structure calculations are considered.

Towards relativistic ECP / DFT description of chemical bonding in E112 compounds: spin-orbit and correlation effects in E112X versus HgX (X=H, Au)

The relativistic effective core potential (RECP) approach combined with the spin-orbit DFT electron correlation treatment was applied to the study of the bonding of eka-mercury (E112) and mercury with hydrogen and gold atoms. Highly accurate small-core shape-consistent RECPs derived from Hartree-Fock-Dirac-Breit atomic calculations with Fermi nuclear model were employed. The accuracy of the DFT correlation treatment was checked by comparing the results in the scalar-relativistic (spin-orbit-free) limit with those of high level scalar-relativistic correlation calculations within the same RECP model. E112H was predicted to be slightly more stable than its lighter homologue (HgH). The E112-Au bond energy is expected to be ca. 25–30 % weaker than that of Hg-Au. The role of correlations and magnetic (spin-dependent) interactions in E112-X and Hg-X (X=H, Au) bonding is discussed. The present computational procedure can be readily applied to much larger systems and seems to be a promising tool for simulating E112 adsorption on metal surfaces.

High resolution spectroscopy and channel-coupling treatment of the A 1Σ+–b 3Π complex of NaRb

The paper presents the study of the fully mixed A 1Σ+–b 3Π complex of the NaRb molecule based on high-resolution sub-Doppler spectroscopy and intensity measurements, ab initio relativistic calculations of energies, transition moments and spin–orbit interactions, as well as an inverted channel-coupling approach (ICCA) deperturbation analysis. A two-laser V-type pump–probe excitation scheme was employed to obtain A←X transition frequencies to 16 A-state vibrational levels from v=6 to v=21 with J from 8 to 23. Additionally, relative intensities in laser-induced A→X fluorescence spectra have been recorded, including progressions with all observable transitions to the ground state vibronic levels, the latter yielding unambiguous v assignment of the A-state levels observed. All experimental rovibronic term values and all measured intensity distributions were embedded in a direct simultaneous weighted nonlinear fitting in the framework of an elaborated ICCA allowing us to obtain deperturbed relativistic diabatic...

The c 3Σ+,b 3Π, and a 3Σ+ states of NaK revisited

We present new c 3Σ+→a 3Σ+ laser induced fluorescence spectra of the NaK molecule, which clearly indicate that v0=20 is the first vibrational level of the c 3Σ+ state lying above v=0 of B 1Π state. These spectra are used in a multistep deperturbation (B 1Π∼c 3Σ+∼b 3Π) procedure to obtain improved a 3Σ+, b 3Π and c 3Σ+ potential energy curves. The deperturbation analysis is confirmed by the calculated electronic B 1Π∼c 3Σ+ and c 3Σ+∼b 3Π spin–orbit matrix elements obtained from many-body multipartitioning perturbation theory employing the relativistic effective potential method.

Multipartitioning many-body perturbation theory calculations on temporary anions: applications to N−2 and CO−

The multipartitioning form of the second-order many-body perturbation theory for state-selective effective Hamiltonians is adapted to stabilization calculations of temporary molecular anionic states. We restrict our attention to the simplest case of a system composed of a closed-shell-like molecule and an electron. Pilot applications to the description of the 2Πg state of the nitrogen molecular anion and the 2Π state of CO− are reported.

Lifetimes and transition dipole moment functions of NaK low lying singlet states: Empirical and ab initio approach

The paper presents experimental D 1∏ state lifetime τv′J′ data and develops empirical and ab initio approaches concerning D 1∏ and B 1∏ lifetimes, as well as D 1∏–X 1∑+, B 1∏–X 1∑+ and D 1∏–A 1∑+ transition dipole moment functions μ(R) of the NaK molecule. Experimental D 1∏(v′,J′) state τv′J′ values for v′ varying from 1 to 22 have been obtained from experimentally measured electric radio frequency-optical double resonance (rf-ODR) signal contours. The rf-ODR signals have been produced by D 1∏←X 1∑+ laser induced optical transition and rf field (1–900 MHz) induced e–f transition within the D 1∏(v′,J′) level. The possibility to determine empirical absolute μ(R) function in a wide R range from experimental τv′J′ dependence on v′ and J′ has been demonstrated; such an approach has been applied to obtain μ(R) for the B 1∏–X 1∑+ transition on which relative intensity data are absent. The empirical D 1∏–X 1∑+μ(R) function has been considerably improved by simultaneous fitting of relative intensity and lifetime d...

Quasirelativistic multipartitioning perturbation theory calculations on electronic transitions in Au2

Quasirelativistic multipartitioning many-body perturbation theory is applied to ab initio calculations on electronic transitions in the gold dimer. Potential energy functions and spectroscopic constants for low-lying excited states and transition dipole moment functions for main radiative decay channels of experimentally observed states are reported.

Communications: Adsorption of element 112 on the gold surface: Many-body wave function versus density functional theory

The applicability of the relativistic density functional theory (RDFT) with conventional generalized gradient and hybrid exchange-correlation functionals to the description of the interactions of element 112 (Cn) and its lighter homolog Hg with a gold surface is assessed. The comparison of Cn-Au (Hg-Au) bond properties for two simple models of adsorption complexes on Au(111) surface obtained by RDFT and accurate many-body calculations indicates a strong underestimation of binding energies by conventional RDFT schemes. This effect provides a possible explanation of the discrepancies between the RDFT-based theoretical and experimental data concerning the thermochromatographic registration of the alpha-decay chain element 114-->Cn.

Relativistic density functional theory modeling of plutonium and americium higher oxide molecules

The results of electronic structure modeling of plutonium and americium higher oxide molecules (actinide oxidation states VI through VIII) by two-component relativistic density functional theory are presented. Ground-state equilibrium molecular structures, main features of charge distributions, and energetics of AnO3, AnO4, An2On (An=Pu, Am), and PuAmOn, n = 6-8, are determined. In all cases, molecular geometries of americium and mixed plutonium-americium oxides are similar to those of the corresponding plutonium compounds, though chemical bonding in americium oxides is markedly weaker. Relatively high stability of the mixed heptoxide PuAmO7 is noticed; the Pu(VIII) and especially Am(VIII) oxides are expected to be unstable.

Ab initio study of temporary anions of benzene and fluorobenzenes using the multipartitioning many-body perturbation theory.

We present an ab initio study of the lowest states of five temporary anions: C6H6(-), C6H5F(-), 1,4-C6H4F2(-), 1,2,3-C6H3F3(-), and 1,3,5-C6H3F3(-). Vertical positions and widths of anionic resonances have been calculated within the stabilization graph approach using the multipartitioning form of the many-body perturbation theory for state-selective effective Hamiltonians restricted to second order (MPPT-R). Good agreement with experimentally derived estimates justifies application of the MPPT-R method for theoretical investigation of haloaromatic temporary anion radicals.