ИСТИНА

The relativistic pseudopotential (RPP) method is often used in calculations of electronic structure, spectra, and various physico-chemical properties of compounds of heavy elements because it allows one to reduce drastically the computational efforts in comparison with the calculations with the Dirac-Coulomb(-Breit) Hamiltonian without significant loss in accuracy. The generalized (Gatchina) versions of the RPPs (GRPPs) were developed at NRC “Kurchatov Institute” - PNPI. They allow one to increase significantly the accuracy of RPP calculations due to the use of different RPP components for valence and outer core electrons with the same spatial and total angular momenta, etc. [1]. Here, the GRPPs are constructed for light elements without excluding any electrons from explicit treatment (“empty-core GRPP”) to simulate the standard relativistic effects, Breit corrections to Coulomb interactions between electrons, and quantum electrodynamic (QED) contributions described by the self-energy and vacuum polarization diagrams [2]. Thus, the nonrelativistic kinetic energy and Coulomb interelectronic interaction operators should be used in the further calculations with these GRPPs. The errors of the GRPP simulation and the contributions of different effects are demonstrated in atomic numerical self-consistent-field calculations in Table 1. Unlike them, direct relativistic calculations with the Dirac–Coulomb(–Breit) Hamiltonian are difficult for molecules, clusters, and crystals due to four-component representation for the wave-function, etc. On the other hand, widely used nonrelativistic calculations with Schrödinger Hamiltonian neglect the relativistic effects which can be essential for some tasks (spin-orbit splittings, spin-forbidden electronic transition moments [3], etc.) This work on the GRPP generation at NRC “Kurchatov Institute” - PNPI has been supported by the Russian Science Foundation (grant No. 20-13-00225). References: 1. A.V. Oleynichenko, A. Zaitsevskii, N.S. Mosyagin, A.N. Petrov, E. Eliav, A.V. Titov, Symmetry 15, 197 (2023). 2. A. Zaitsevskii, N.S. Mosyagin, A.V. Oleynichenko, E. Eliav, Int. J. Quant. Chem., e27077 (2022). 3. N.S. Mosyagin, A.V. Oleynichenko, A. Zaitsevskii, A.V. Kudrin, E.A. Pazyuk, A.V. Stolyarov, J. Quant. Spectrosc. Radiat. Transfer 263, 107532 (2021).