A two-step method of calculation of the electronic structure of molecules with heavy atoms: Theoretical aspect

Abstract

=An approach for a space-separated calculation of the wave function in the valence and core regions of a molecule is proposed. As the first step, the calculation of the orbitals (or two-component spinors in the relativistic case) in the valence region by the effective core potential (ECP) method is performed. Then, it is followed by a restoration of orbitals (four-component spinors) expanded on spherical harmonics in the core regions of heavy atoms. Theoretical questions of the variational calculation of the molecular orbitals are considered in some core region limited by a sphere. Inclusion from the electronic cloud outside this region is reduced by the necessity of taking into account the orthonormality and boundary conditions together with an effective external field in respect to the selected core region. This method may be used for calculation of matrix elements of operators that are singular near nuclei (P, T-odd interactions, hyperfine structure, etc.). A substantial computational saving can be reached because the method enables, by the most optimal way, to combine the advantages of two well-developed approaches: molecular ECP

Theoretical study ofHfF+in search of the electron electric dipole moment

“…Recently, the E eff value for the 3 ∆ 1 state was estimated in the scalar-relativistic approximation by Meyer et al [16] and the method used for calculation of E eff is close in essence to that developed by us earlier [17] and applied to first two-step calculations of the PbF molecule [14,17]. In the present work, a more reliable value of E eff is calculated using the advanced two-step techniques developed by us later [18,19,20,21] is not the ground state, its radiative lifetime is also required. In the present work these data are obtained, though precise studying of the compounds with transition elements is a difficult problem for modern molecular theory.…”

“…Before calculating core properties the shapes of the fourcomponent molecular spinors are restored in the inner core region after the two-component GRECP calculation of the molecule. For this purpose the nonvariational onecenter restoration (NOCR) method [17,18,20,21,27,33] is applied.…”

Cadmium–carbon wavenumber analysis using B3LYP level theory calculations in investigations of dimethylcadmium decomposition

“…However, experimental support of the second Cd-C bond fission via reaction (2) was not evident with our detectors because the electronic Raman spectrum of the Cd atom is not detectable, i.e. since atomic Cd has a closed outer shell, and its lifetime for the transition between the ground state and the first excited state is too short to be detected in our system.…”

“…[13] Although the homolytic fission reactions (1) and (2) are likely the dominant reactions in the gas phase, the suggested pathways for the decomposition of other group II alkyls often include additional reactions contributing to the deposition process. [14] Computational chemistry is a good companion to assist in designing and interpreting experiments and to explore various reaction pathways.…”

Enhancement of the electron electric dipole moment in Eu2+

“…The polarization of the innercore electrons is usually negligible. These circumstances allow us to use a two-step technique, advanced by our group [23][24][25][26][27] and recently applied for calculation of E eff in molecular systems [28,29]. At the first step we exclude inactive inner-core orbitals from correlation calculation with the help of a very accurate generalized relativistic effective core potential method (GRECP) [30][31][32] to reduce computational efforts.…”