Relativistic Coupled Cluster Approach to Actinide Molecules

6 Relativistic Coupled Cluster Approach to Actinide Molecules 

While CC methods may be the best quantum chemistry can offer, they are also the most expensive, limiting the size of systems treatable by them. Exploration of larger systems became possible in recent years with the advent of schemes where only the active center of a large compound is treated by IHFSCC, while most of the compound is handled by simpler methods the active center is then embedded in the potential created by its environment. This approach was applied to the spectrum of CUO with 4 rare gas atoms, simulating the effect of rare gas matrices on the spectra of the molecule [29] and to the spectmm of uranyl in the CS2UO2CI4 crystal [30]. 

The no-virtual-pair Dirac-Coulomb-Breit Hamiltonian, correct to second order in the fine-structure constant a, provides the framework for four-component methods, the most accurate approximations in electronic structure calculations for heavy atomie and molecular systems, ineluding aetinides. Electron correlation is taken into aeeount by the powerful coupled eluster approaeh. The density of states in actinide systems necessitates simultaneous treatment of large manifolds, best achieved by Fock-space coupled eluster to avoid intruder states, which destroy the convergence of the CC iterations, while still treating a large number of states simultaneously, intermediate Hamiltonian sehemes are employed. 

van Gunsteren, and Z. Chaia, Recent advances in computational actinoid 

Cao and M. Dolg, Relativistic energy-consistent ah initio pseudopotentials as tools for quantum chemical investigations of actinide systems, Coord. Chem. Rev. 250,900 (2006). 

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