We present the first application of the variationally orbital optimized antisymmetric product of 1-reference orbital geminals (vOO-AP1roG) method to singlet-state actinide chemistry. We assess the accuracy and reliability of the AP1roG ansatz in modelling the ground-state electronic structure of small actinide compounds by comparing it to standard quantum chemistry approaches. Our study of the ground state spectroscopic constants (bond lengths and vibrational frequencies) and potential energy curves of actinide oxides (UO22+ and ThO2) as well as the energetic stability of ThC2 isomers reveals that vOO-AP1roG describes the electronic structure of heavy-element compounds accurately, at mean-field computational cost.

The chemical bond is an important local concept to understand chemical compounds and processes. Unfortunately, like most local concepts, the chemical bond and the bond order do not correspond to any physical observable and thus cannot be determined as an expectation value of a quantum chemical operator. We recently demonstrated [Boguslawski et al., J. Chem. Theory Comput., 2013, 9, 2959–2973] that one- and two-orbital-based entanglement measures can be applied to interpret electronic wave functions in terms of orbital correlation. Orbital entanglement emerged as a powerful tool to provide a qualitative understanding of bond-forming and bond-breaking processes, and allowed for an estimation of bond orders of simple diatomic molecules beyond the classical bonding models. In this article we demonstrate that the orbital entanglement analysis can be extended to polyatomic molecules to understand chemical bonding.

The accurate description of the complexation of the CUO molecule by Ne and Ar noble gas matrices represents a challenging task for present-day quantum chemistry. Especially, the accurate prediction of the spin ground state of different CUO–noble-gas complexes remains elusive. In this work, the interaction of the CUO unit with the surrounding noble gas matrices is investigated in terms of complexation energies and dissected into its molecular orbital quantum entanglement patterns. Our analysis elucidates the anticipated singlet–triplet ground-state reversal of the CUO molecule diluted in different noble gas matrices and demonstrates that the strongest uranium–noble gas interaction is found for CUOAr4 in its triplet configuration.

The chemical bond is an important local concept to understand chemical compounds and processes. Unfortunately, like most local concepts, the chemical bond and the bond order do not correspond to any physical observable and thus cannot be determined as an expectation value of a quantum chemical operator. We recently demonstrated [Boguslawski et al., J. Chem. Theory Comput., 2013, 9, 2959–2973] that one- and two-orbital-based entanglement measures can be applied to interpret electronic wave functions in terms of orbital correlation. Orbital entanglement emerged as a powerful tool to provide a qualitative understanding of bond-forming and bond-breaking processes, and allowed for an estimation of bond orders of simple diatomic molecules beyond the classical bonding models. In this article we demonstrate that the orbital entanglement analysis can be extended to polyatomic molecules to understand chemical bonding.

The accurate description of the complexation of the CUO molecule by Ne and Ar noble gas matrices represents a challenging task for present-day quantum chemistry. Especially, the accurate prediction of the spin ground state of different CUO–noble-gas complexes remains elusive. In this work, the interaction of the CUO unit with the surrounding noble gas matrices is investigated in terms of complexation energies and dissected into its molecular orbital quantum entanglement patterns. Our analysis elucidates the anticipated singlet–triplet ground-state reversal of the CUO molecule diluted in different noble gas matrices and demonstrates that the strongest uranium–noble gas interaction is found for CUOAr4 in its triplet configuration.

We present the first application of the variationally orbital optimized antisymmetric product of 1-reference orbital geminals (vOO-AP1roG) method to singlet-state actinide chemistry. We assess the accuracy and reliability of the AP1roG ansatz in modelling the ground-state electronic structure of small actinide compounds by comparing it to standard quantum chemistry approaches. Our study of the ground state spectroscopic constants (bond lengths and vibrational frequencies) and potential energy curves of actinide oxides (UO22+ and ThO2) as well as the energetic stability of ThC2 isomers reveals that vOO-AP1roG describes the electronic structure of heavy-element compounds accurately, at mean-field computational cost.