First Principle Based Modeling and Interpretation of Chemical Experiments on Superheavy Element Identification

Abstract

Our latest advances in studies of actinide and superheavy element (SHE) chemistry using the shapeconsistent two-component small-core relativistic pseudopotential (RPP) method and two-component relativistic density functional theory (2c-RDFT) are summarized. The features of these elements, due to large relativistic effects, are emphasized. The RPP model, leaving for explicit correlation treatment with both valence and subvalence (outercore) electrons, accounts for the finite nuclear size and incorporates relativistic effects (including the bulk of Breit interactions), providing a good basis for attaining optimal accuracy/cost ratio in the cases of large and strongly interfering relativistic and correlation effects, intrinsic for the heavy-atom compounds. The RPP/2c-RDFT approach allows one to solve the outercore-valence many-electron problem with moderate computational expenses while using practically exhaustive basis sets, optimized for the case of large differences between nl(j=l+1/2) and nl(j=l-1/2) oneelectron states. Because of the exceptional role of thermochromatography on gold in the experiments on the "chemical" identification of SHEs with atomic numbers Z ≥ 112, the main attention was paid to the description of the SHE -gold interactions. Adsorption energies of SHEs on a gold surface were estimated using the cluster model. Its reliability was improved by monitoring the charge distributions in the vicinity of the adsorption site, taking account of the effects of the relaxation of the cluster compatible with its embedding into the crystal. The resulting desorption energy estimates for elements 113 and 120 single atoms from gold surface are substantially lower than the previously reported values.

Generalized relativistic effective core potentials for superheavy elements

“…The lack of experimental data on molecular properties of SHE compounds makes it impossible to estimate the accuracy of quantum chemical calculations by comparison of their results with the measured values. Although there are many experimental data for lighter analogues of SHEs, they are not quite appropriate for the calibration because huge relativistic effects for SHEs can change trends down a group in the Periodic table, as one can see on example of elements Nh and Fl composing a particular subperiod in seventh period . Therefore, high quality of calculations with SHE compounds is highly desirable.…”