Fully relativistic study of polyatomic closed shell E121X3 (X = F, Cl, Br) molecules: effects of Gaunt interaction, relativistic effects and advantages of an exact-two component (X2C) hamiltonian

Alan Sena Pinheiro; Ricardo Gargano; Paulo Henrique Gomes Dos Santos; Luiz Guilherme Machado de Macedo

doi:10.1007/s00894-021-04861-7

Fully relativistic study of polyatomic closed shell E121X₃ (X = F, Cl, Br) molecules: effects of Gaunt interaction, relativistic effects and advantages of an exact-two component (X2C) hamiltonian

J Mol Model. 2021 Aug 26;27(9):262. doi: 10.1007/s00894-021-04861-7.

Authors

Alan Sena Pinheiro¹, Ricardo Gargano², Paulo Henrique Gomes Dos Santos³, Luiz Guilherme Machado de Macedo⁴

Affiliations

¹ Programa de Pós-Graduação em Química/PPGQ, Instituto de Ciências Exatas e Naturais (ICEN), Universidade Federal Do Pará (UFPA), Belém, PA, 66075-110, Brazil.
² Instituto de Física, Universidade de Brasília (UnB), P.O. Box 04455, Brasília, DF, 70919-970, Brazil.
³ Campus Centro Oeste Dona Lindu (CCO/UFSJ) Divinópolis, Universidade Federal de São João del Rei, São João del Rei, MG, 35501-296, Brazil.
⁴ Campus Centro Oeste Dona Lindu (CCO/UFSJ) Divinópolis, Universidade Federal de São João del Rei, São João del Rei, MG, 35501-296, Brazil. lgm@ufsj.edu.br.

PMID: 34435260
DOI: 10.1007/s00894-021-04861-7

Abstract

In this study, all electron relativistic calculations with 4-component Dirac-Coulomb-Breit (DCB), 4-component Dirac-Coulomb (DC), Dyall's spin-free Dirac-Coulomb (SFDC), exact two-component (X2C) and Levy-Leblond non-relativistic hamiltonians calculations were performed in polyatomic closed shell E121X₃ (X = F, Cl, Br) within density functional theory (DFT) with hybrid functional B3LYP, where E121 is the superheavy element (SHE) with Z = 121. The aims of this study were to investigate relativistic effects in polyatomic E121X₃ (X = F, Cl, Br) and verify the importance of Gaunt effects. The results demonstrate that although the effect of Gaunt interaction is small on change equilibrium bond lengths and bonding, it is important to obtain reliable vibrational frequencies. Moreover, it is possible to use the X2C spin-free hamiltonian to lower computational costs in a fully relativistic investigation of polyatomics including the SHE of the 8th period. Finally, a comparison between electron localization function (ELF) analysis and Mulliken population analysis suggests bonding similarity between LaBr₃ and E121Br₃. Graphical Abstract Relativistic 4-Component calculations suggest bond similarity between LaBr₃ and E121Br₃.

Keywords: 4-Component calculations; DFT; Electron localization function; Gaunt interaction; Periodic trends; Relativistic effects; Superheavy element E121; X2C hamiltonian.