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The potential energy curves and the NMR properties: nuclear spin–spin coupling constants and nuclear shielding constants have been calculated for Zn2, Cd2 and Hg2 dimers using density functional theory. The calculations have been carried out using the relativistic four-component Dirac–Coulomb Hamiltonian, and, in the case of energy curves, also relativistic effective core potentials. In case of NMR parameters, the relativistic effects turned out to be critically important even for the lightest dimer, Zn2. The importance of the spin–orbit coupling depends on the internuclear distance: these effects tend to be significant for short internuclear distances. [ABSTRACT FROM AUTHOR]

Advanced relativistic quantum chemistry calculations were used for the first time to provide accurate determinations of fundamental molecular properties for two moscovium halides (McX, X = F and Cl). The recommended values presented here were obtained with the X2C-MMF-CCSD-T/RPF-4Z level of theory. Thus, we determined an equilibrium bond length (re) of 2.287 Å, an equilibrium dipole moment (μe) of 6.59 D and a harmonic vibrational frequency (ωe) of 405 cm−1 for McF. On the other hand, the results for McCl show re, μe and ωe values equal to 2.728 Å, 7.46 D and 244 cm−1, respectively. The same Mc+–X− polarity is predicted in molecules of both halides. The equilibrium dissociation energies attained in X2C-MMF-(FS)CCSD/RPF-4Z calculations are 4.04 and 3.45 eV for McF and McCl, respectively. Therefore, the Mc–F and Mc–Cl bonds are predicted to be slightly stronger than Bi–F and Bi–Cl ones, respectively. Finally, the huge values obtained for dipole moments in the molecules studied strongly suggest that moscovium halides are predominantly ionic compounds. [ABSTRACT FROM AUTHOR]

Nonrelativistic and relativistic variational calculations of energies and ionization potentials of the ground state of helium-like ions with nuclear number Z = 2−20 have been performed. All leading corrections to the total energy have been calculated, including the contribution of electron correlations, relativistic and quantum-electrodynamics corrections, and contributions due to the finite nuclear size (field shift) and finite nuclear mass (nuclear recoil) effects. Relativistic wave functions were calculated using the Dirac–Coulomb–Breit Hamiltonian. [ABSTRACT FROM AUTHOR]

The titular calculations show that charges at metal atoms M are apparently the main factor governing the nature of M⋅⋅⋅M interactions in two-nuclear coinage-metal complexes, and there are certain critical values of positive charges on M atoms, on exceeding which the pair-wise M⋅⋅⋅M interactions and/or the binding between M atoms in such complexes become repulsive despite negative formation energies of such complexes, short M-M internuclear distances, and the existence of a bond critical point (BCP) between M atoms. [ABSTRACT FROM AUTHOR]

This paper completes the cycle of our calculations of the radiative recombination and photoionization data for tungsten ions. Presented here are the photoionization and radiative recombination cross sections, radiative recombination rate coefficients, and radiated power loss rate coefficients for ten tungsten impurity ions from W14+ to W23+. These data are required in diagnostics and modeling fusion plasmas studied in such devices as ITER, ASDEX Upgrade, and EBIT. Partial photoionization cross sections have been fitted by an analytical expression with five fit parameters tabulated here. Total radiative recombination cross sections are presented in the electron energy range from 1 eV to ~80 keV. Radiative recombination rates and radiated power loss rates are given in the temperature range from 104 K to 109 K. Calculations have been performed on the basis of the fully relativistic treatment of photoionization and radiative recombination taking into account all significant multipoles of the radiative field. Electron wave functions have been obtained by the Dirac-Fock method with the proper consideration of the electron exchange. The relativistic Maxwell-Jüttner distribution of continuum electrons has been used in calculations of radiative recombination rates and radiated power loss rates. This decreases values of the rates noticeably at a high temperature as compared to the usual non-relativistic Maxwell-Boltzmann distribution. [ABSTRACT FROM AUTHOR]

Highlights: [•] The geometrical structure of An@C40 (An=Th–Md) complexes was found. [•] The trends of stability variation of the complexes were obtained. [•] The An5f participation in bonding is essential for the complexes of Th and Pa. [Copyright &y& Elsevier]

Abstract: The geometry optimization of the neutral molecules An@C28 (An=Th – Md) was carried out using the DFT based Dmol3 method. For the calculations of electronic structure of these complexes we used the fully relativistic discrete variational method (RDV). The systems containing Th, Pa, U, Np and Pu have considerable energetic stability. It was found, that the 5f-orbitals contribution to chemical bonding is close to that of the 6d-states for the first half of An@C28 row. The effective charges on the atoms were calculated using integral scheme incorporated in RDV and Hirshfeld procedure of DMol3. [ABSTRACT FROM AUTHOR]

Abstract: Spectroscopic properties of group-1 M2 and MAu (M=K, Rb, Cs, Fr, and element 119) were calculated using the 4c-DFT method. The results show that the relativistic contraction and stabilization of the ns(M) AO result in the inversion of trends both in atomic and molecular properties in group 1 beyond Cs. Electronegativity χ of the elements proves to decrease from Cs, the most electropositive element of all elements, to element 119, with its χ value approaching that of Na. Due to the largest relativistic effects on the 8s(119) AO in group 1, bonding in (119)2 appears to be stronger than that of K2, while bonding in 119Au should be the weakest out of all group-1 MAu. Using calculated dissociation energies of M2, sublimation enthalpies, ΔH sub, of Fr of 77kJ/mol and element 119 of 94kJ/mol were estimated using a linear correlation between these quantities in the chemical group. Using the M–Au binding energies, the adsorption enthalpies, −ΔH ads, of 106kJ/mol on gold, 76kJ/mol on platinum, and 63kJ/mol on silver were estimated for element 119 via a correlation with known ΔH ads in the chemical group. These moderate ΔH ads values are indicative of a possibility of chromatography adsorption studies of element 119 on the noble metal surfaces. [Copyright &y& Elsevier]

Abstract: The Auger electron emission rates for Li- and Be-like ions with and configurations respectively have been calculated for ions in the range using a scaling procedure on the already available relativistic radial matrix elements for a single vacancy in the K-shell. The results are compared with earlier theoretical data and are found to be in reasonably good agreement for most of the elements under consideration. [Copyright &y& Elsevier]

Work on computational NMR recently carried out at our Laboratory in Padova is reviewed. We summarize our results concerning the calculation of NMR properties (chemical shifts and spin–spin coupling constants) in a variety of contexts, from the structure elucidation of complex organic molecules or molecules containing heavy atoms to weakly interacting species, such as those involved in hydrogen bonding or van der Waals CH-π interactions. We also present some original results, viz. the calculated 1H and 13C spectra of the putative natural substance nimbosodione, the first examples of calculated 181Ta chemical shifts, spin–spin couplings in $$\hbox{Hg}_{4}^{2+}$$ and through-space coupling constants involving 205Tl. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we discuss the performance of molecular basis sets consisting of atomic centred (AC) functions augmented with bond centred (BC) functions in relativistic and non-relativistic calculations carried out at the Hartree–Fock and several correlated levels of approximation. While usually non-correlated calculations employing BC functions can be performed at a lower computational cost as compared with those making use of energy optimized AC basis sets, the correlated calculations are always more accurate and less expensive with the latter. It is demonstrated that both correlated or non-correlated calculations always benefit from the addition of a few BC functions with a moderate increase of computational effort. The performance of basis sets containing even-tempered BC functions is also studied and their usage is advocated in case of relativistic calculations. [Copyright &y& Elsevier]

Gas phase emission spectra of the hitherto unknown free radical PbLi have been measured in the NIR range with a Fourier-transform spectrometer. The emissions were observed from a fast flow system in which lead vapor in argon carrier gas was passed through a microwave discharge and mixed with lithium vapor in an observation tube. Five electronic transitions have been found in the wavenumber range 3800–10 000 cm−1. Bands from two excited states to the ground state were measured at high spectral resolution such that rotational analyses could be performed and accurate molecular parameters derived. In order to aid in the analysis of the experimental data, a series of relativistic configuration interaction calculations has been carried out to obtain potential curves for the low-lying states of PbLi and also electric dipole transition moments connecting them. As in the lighter molecules of this group, CLi and SiLi, the ground state of PbLi is found to be X4Σ−(X1 1/2,X2 3/2) with a spin splitting of about 2000 cm−1. The first excited state is A2Π1/2 (A 1/2), and two observed band systems are assigned to the transitions A→X1 and A→X2. Two more excited states, B2Π3/2 (B 3/2) and C 1/2, are identified from the observed spectra with the help of the computed data, and their spectroscopic constants are determined. In contrast to PbH and PbF, the ab initio results indicate a very complicated low-energy electronic structure for the PbLi radical, with 19 bound electronic states calculated to lie below 3 eV. [Copyright &y& Elsevier]

The E1M1 transition rate of the $2s2p{\ }^{3}{P}_{0}\to 2{s}^{2}{\ }^{1}{S}_{0}$ line in beryllium-like ions has been calculated within the framework of relativistic second-order perturbation theory. Both multiconfiguration and quantum-electrodynamical computations have been carried out independently to better understand and test for all major electron–electron correlation contributions in the representation of the initial, intermediate and final states. By comparing the results from these methods, which agree well for all ions along the beryllium isoelectronic sequence, the lifetime of the metastable 2 s 2 p ^3 P _0 level is found to be longer by about 2–3 orders of magnitude for all medium and heavy elements than was estimated previously. This makes the ^3 P _0 level of beryllium-like ions to one of the longest living (low-lying) electronic excitations of a tightly bound system with potential applications for atomic clocks and in astro physics and plasma physics.

Spectra of the Δv = 0 sequences of the A1/2 → X 2 1/2 transitions of NaTe (a) and KTe (b). • We report on relativistic SO-CI calculations of spectroscopic properties of the hitherto unknown radicals NaTe and KTe. • The NIR emission spectra of NaTe and KTe were measured with a high-resolution FT spectrometer. • Electronic energies and vibrational constants for three states of each molecule were obtained. • One band of NaTe was measured at high resolution and analysed. Gas phase emission spectra of the hitherto unknown radicals NaTe and KTe have been measured in the NIR range with a Fourier-transform spectrometer. The emissions were observed from a fast-flow system in which tellurium vapor in argon carrier gas was passed through a microwave discharge and mixed with sodium or potassium vapor in an observation tube. Excitation of the radicals mostly occurred by near-resonant E-E energy exchange from added metastable oxygen O 2 (a 1Δ g). Like for the previously studied LiTe molecule, for both radicals two systems of blue-degraded bands were measured in the range 4500–8500 cm−1. They were assigned to the transitions A 2Σ+(A 1/2) → X 1 2Π 3/2 (X 1 3/2) and A 2Σ+(A 1/2) → X 2 2Π 1/2 (X 2 1/2). For all four subsystems vibrational analyses were performed which yielded ground state splittings of 2265.39(13) cm−1 (NaTe) and 1544.19(11) cm−1 (KTe) as well as A 2Σ+ state energies of 7935.98(9) cm−1 (NaTe) and 6404.71(11) cm−1 (KTe) and vibrational constants of the X 1 3/2, X 2 1/2 and A 1/2 states of both molecules. The 0-0 bands of both sub-transitions of NaTe were measured at high spectral resolution and rotationally analyzed. In order to aid in the analysis of the experimental data, a series of relativistic configuration interaction calculations has been carried out to obtain potential curves for the low-lying states of NaTe and KTe and also electric dipole transition moments connecting them. [ABSTRACT FROM AUTHOR]

• Investigations of the complex geometry are inconclusive. • Mercury atom has significant impact on the NMR parameters of water molecule. • σ Hg equilibrium geometry of water-mercury complex is 12 ppm smaller than in isolated Hg atom. Potential energy surface of the Hg ⋯ H 2 O dimer was studied by means of CCSD(T) and DFT methods. After that nuclear shielding constants and nuclear spin-spin coupling constants have been calculated at the DFT level. All the calculations were carried out with four-component relativistic Dirac-Coulomb Hamiltonian. DFT produces a global minimum with mercury atom on C 2 v axis of water molecule, but this is not confirmed by CCSD(T). All of the calculated shielding constants increase with the increase in the distance between mercury and oxygen atoms. σ Hg at equilibrium geometry is 12 ppm smaller than in isolated mercury atom. [ABSTRACT FROM AUTHOR]