MCDHF/DC+B-adjusted pseudopotentials for lanthanides and quantum chemical investigations of lanthanide compounds with unusual electronic structure

基于对有限核Dirac-Coulomb哈密顿量的自洽处理和对Breit相互作用低频极限的微扰处理，从多组态Dirac-Hartree-Fock参考数据推导出La(Z=57)到Lu(Z=71)元素的相对论能量相容小核(28个核心电子)从头算赝势。目标是对从中性原子到半核轨道4s、4p、4d、5s和5p上有空洞的高电荷态离子的各种组态的总能量达到优于0.01 eV的精度。对于单组分和双组分计算，将推导出具有高达四重Zeta性质的一般压缩原子自然轨道基组。赝势将根据相应的全电子从头计算数据和实验数据，在原子和分子(例如，选定的一元氢化物、单氧化物和一氟化物)关联计算中进行校准。赝势将被用于研究具有不寻常成键状态的稀土体系，例如，双(戊二烯)Ce(戊二烯)、Ce(双酞菁)和Ce(三(环戊二烯)阳离子)和双原子一氧化钇。在第一种情况下，将研究Ce的氧化态。在第二种情况下，将检验Yb子组态与4f壳层中13和14个电子的组态混合是否导致了异常的0基态光谱常数，表现出Yb(2)4f13 6s1 O(2-)典型的键长和Yb(2)4F14 O(2-)典型的振动频率。

Relativistic energy-consistent small-core (28 core electrons) ab initio pseudopotentials will be derived for the lanthanide elements La (Z=57) to Lu (Z=71) from multi-configuration Dirac-Hartree-Fock reference data based on the self-consistent treatment of the finite nucleus Dirac-Coulomb Hamiltonian and a perturbative treatment of the low-frequency limit of the Breit interaction. The goal is to reach an accuracy of better than 0.01 eV for the total energies of various configurations ranging from the neutral atom to highly charged ions with holes in the semi-core orbitals 4s, 4p, 4d, 5s and 5p. Generally contracted atomic natural orbital basis sets, for one- and two-component calculations, with up to quadruple-zeta quality will be derived. The pseudopotentials will be calibrated in atomic as well as molecular (e.g., selected monohydrides, monoxides, and monofluorides) correlated calculations against corresponding all-electron ab initio reference data as well as against experimental data if available.The pseudopotentials will be applied to study lanthanide systems with unusual bonding situations, e.g., the sandwich compounds cerium bis(pentalene), cerium bis(phthalocyanine) and cerium tris(cyclopentadienly) cation and diatomic ytterbium monoxide. In the first case the oxidation state of Ce will be investigated. It will be checked if the system has a similar Ce(3+) Kondo-type open-shell singulet ground state as cerium bis(cyclooctatetraene), cerocene.In the second case it will be examinated if the configurational mixing between Yb subconfigurations with 13 and 14 electrons in the 4f shell leads to the unusual spectroscopic constants of the 0+ ground state, exhibiting a bond length typical for Yb(2+) 4f13 6s1 O(2-) and a vibrational frequency typical for Yb(2+) 4f14 O(2-).