Ab initio study of electronic states and radiative properties of the AcF molecule.

Relativistic coupled-cluster calculations of the ionization potential, dissociation energy, and excited electronic states under 35 000 cm-1 are presented for the actinium monofluoride (AcF) molecule. The ionization potential is calculated to be IPe = 48 866 cm-1, and the ground state is confirmed to be a closed-shell singlet and thus strongly sensitive to the T,P-violating nuclear Schiff moment of the Ac nucleus. Radiative properties and transition dipole moments from the ground state are identified for several excited states, achieving a mean uncertainty estimate of ∼450 cm-1 for the excitation energies.

Compound-tunable embedding potential method: analysis of pseudopotentials for Yb in YbF, YbF, YbCl and YbCl crystals.

The compound-tunable embedding potential (CTEP) method developed in [Lomachuk , , 2020, , 17922; Maltsev , , 2021, , 205105] to describe the electronic structure of fragments and point defects in materials is applied to crystals containing periodically arranged lanthanide atoms, which can have an open 4f-shell. We consider YbF, YbF, YbCl, and YbCl crystals for the pilot CTEP studies such that 4f-electrons are not treated explicitly at the CTEP generation stages. Instead, the pseudopotentials with 60 and 59 electrons in the core for Yb(II) and Yb(III), correspondingly, are applied and the latter treats the "4f-hole-in-core".

Accurate ab initio calculations of RaF electronic structure appeal to more laser-spectroscopical measurements.

Recently, a breakthrough has been achieved in laser-spectroscopic studies of short-lived radioactive compounds with the first measurements of the radium monofluoride molecule (RaF) UV/vis spectra. We report results from high-accuracy ab initio calculations of the RaF electronic structure for ground and low-lying excited electronic states. Two different methods agree excellently with experimental excitation energies from the electronic ground state to the Π and Π states, but lead consistently and unambiguously to deviations from experimental-based adiabatic transition energy estimates for the Σ excited electronic state, and show that more measurements are needed to clarify spectroscopic assignment of the Δ state.

Actinide and lanthanide molecules to search for strong CP-violation.

The existence of the fundamental CP-violating interactions inside the nucleus leads to the existence of a nuclear Schiff moment. The Schiff moment potential corresponds to the electric field localized inside the nucleus and directed along its spin. This field can interact with electrons of an atom and induce the permanent electric dipole moment (EDM) of the whole system.

Compound-tunable embedding potential: which oxidation state of uranium and thorium as point defects in xenotime is favorable?

Modern strategies for the safe handling of high level waste (HLW) and its long-term disposal in deep geological formations include the immobilization of radionuclides in the form of mineral-like matrices. The most promising matrices for the immobilization of actinides are ceramic forms of waste based on phosphate minerals such as monazite, xenotime, and cheralite. However, the mechanism of substitution of lanthanides and Y by actinides in phosphate minerals is not entirely clear.

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.

Relativistic effective core potential calculations of Hg and eka-Hg (E112) interactions with gold: spin-orbit density functional theory modeling of Hg-Aun and E112-Aun systems.

Interactions of eka-Hg (E112) and Hg atoms with small gold clusters were studied in the frame of the relativistic effective core potential model using the density functional theory (DFT) approach incorporating spin-dependent (magnetic) interactions. The choice of the exchange-correlation functional was based on a comparison of the results of DFT and large-scale coupled cluster calculations for E112Au and HgAu at the scalar relativistic level. A close similarity between the E112Aun and HgAun equilibrium structures was observed.

Is E112 a relatively inert element? Benchmark relativistic correlation study of spectroscopic constants in E112H and its cation.

We report the first results of relativistic correlation calculation of the spectroscopic properties for the ground state of E112H and its cation in which spin-orbit interaction is taken into account non-perturbatively. Studying the properties of E112 (eka-Hg) is required for chemical identification of its long-lived isotope, (283)112. It is shown that appropriate accounting for spin-orbit effects leads to dramatic impact on the properties of E112H whereas they are not so important for E112H(+).

In search of the electron electric dipole moment: relativistic correlation calculations of the P,T-violating effect in the ground state of HI+.

We report the first results of ab initio relativistic correlation calculation of the effective electric field on the electron, E(eff), in the ground state of the HI+ cation. This value is required for interpretation of the suggested experiment on the search for the electron electric dipole moment. The generalized relativistic effective core potential, Fock-space relativistic coupled cluster with single and double cluster amplitudes (RCC-SD), and spin-orbit direct configuration interaction (SODCI) methods are used, followed by nonvariational one-center restoration of the four-component wave function in the iodine core.

Accounting for correlations with core electrons by means of the generalized relativistic effective core potentials: atoms Hg and Pb and their compounds.

A way to account for correlations between the chemically active (valence) and innermore (core) electrons in the framework of the generalized relativistic effective core potential (GRECP) method is suggested. The "correlated" GRECP's (CGRECP's) are generated for the Hg and Pb atoms. Only correlations for the external 12 and 4 electrons of them, correspondingly, should be treated explicitly in the subsequent calculations with these CGRECP's whereas the innermore electrons are excluded from the calculations.

Calculation of P, T-odd effects in 205TlF including electron correlation.

A method and codes for two-step correlation calculations of heavy-atom molecules have been developed, employing the generalized relativistic effective core potential (GRECP) and relativistic coupled cluster (RCC) methods at the first step, followed by nonvariational one-center restoration of proper four-component spinors in the heavy cores. Electron correlation is included for the first time in an ab initio calculation of the interaction of the permanent P,T-odd proton electric dipole moments with the internal electromagnetic field in a molecule. Inclusion of electron correlation by GRECP/RCC has a major effect on the P,T-odd parameters of 205TlF, decreasing M by 17% and X by 22%.