Relativistic Ab-Initio Model Potential Calculations for Molecules and Embedded Clusters

Relativistic Ab-Initio Model Potential Calculations for Molecules and Embedded Clusters. 

Relativistic Ab Initio Model Potential embedded cluster calculations on the structure and spectroscopy of local defects created by actinide impurity ions in solid hosts are the focus of attention here. They are molecular like calculations which include host embedding effects and electron correlation effects, but also scalar and spin-orbit coupling relativistic effects, all of them compulsory for a detailed understanding of the large manifolds of states of the 5f the 5f 6d configurations. The results are aimed at showing the potentiality of Relativistic Quantum Chemistry as a tool for prediction and interpretation in the field of solids doped with heavy element impurities. 

A basic, old idea of Chemistry is that only a few electrons of an atom or a molecule are directly relevant to its chemical properties. Another basic, newer idea of the Chemistry of heavy elements is that relativity is necessary for its understanding. While the first is a very powerful simplifying idea, the second one increases the complexity of prediction and analysis in Chemistry. The ability of Effective Core Potentials (ECPs) to be, at the same time, the computational realisation of the first idea, and a means to implement very good simplifications of the most rigorous equations of relativistic Quantum Chemistry, lead them to be as popular as they are nowadays. A deep insight into this is offered to the reader in the previous volume of this collection [1]. 

Effective Core Potential methods are classified in two families, according to their basic grounds. On the one hand, the Pseudopotential methods (PP) rely on an orbital transformation called the pseudoorbital transformation and they are ultimately related to the Phillips-Kleinman equation [2]. On the other hand, the Model Potential methods (MP) do not rely on any pseudoorbital transformation and they are ultimately related to the Huzinaga-Cantu equation [3,4]. The Ab Initio Model Potential method (AIMP) belongs to the latter family and it has as a 

The AIMP method as a common strategy for effective core potential calculations in molecules and for embedded cluster calculations, has been detailed and reviewed [17]. In this paper, we will pay special attention to its applications in the field of structure and spectroscopy of crystal defects created by actinide element impurities, where relativistic effects are a determinant factor, electron correlation and host embedding effects are also key elements, and not only the ground state but also large manifolds of hundreds of excited states are involved in the chemical and physical processes of interest. 

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Seijo, L., Barandiatan, Z. Relativistic ab initio model potentials calculations for molecules and embedded clusters. In Schwerdtfeger, P. (ed.) Relativistic Electronic Structure Theory, Part I, pp. 417-475. Elsevier, Amsterdam (2002)... 

Seijo L, Barandiaran Z. Relativistic Ab-Initio Model Potential Calculations for Molecules and Embedded Clusters. In Schwerdtfeger P, editor. Relativistic Electronic Structure Theory Part 2. Applications. Amsterdam Elsevier 2004. p. 417-475. 

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