Quantum chemical study of lanthanide and actinide impurities in ionic crystals.

DIPC Seminars

Speaker

Dr. Fernando Ruipérez, Department of Physics, Stockholm University, AlbaNova University Centre, Stockholm, Sweden.

When

2010/04/12
14:00

Place

onostia International Physics Center (DIPC).Paseo Manuel de Lardizabal, 4 (nearby the Facultad de Quimica), Donostia

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The interest on the f(n) , f(n-1)d(1) and f(n-1)s(1) local electronic states of lanthanide and actinide impurities in ionic crystals has been growing in the last few years. The electronic transitions which occur upon visible and UV excitation are involved in a variety of phenomena of technological interest which are not always fully understood. Thus, theory and experiments become particularly complementary in this context. It is nowadays possible to calculate the local geometry around an f-element impurity in an ionic host at ambient and high pressures from first principles, using wavefunction based methods of relativistic quantum chemistry in combination with quantum mechanical embedding. The accuracy of the theoretical results can only be assured if the methods fulfill the following requirements: relativistic effects including spin-orbit coupling must be considered simultaneously with valence electron correlation. Finally, the effects of the embedding host crystal must be considered as well. These requirements are met by the ab initio model potential method (AIMP),[1] which is formulated as an effective core potential method that can include spin-orbit relativistic effects and also as an embedding technique useful to describe the quantum mechanical effects of a set of host lattice ions which are represented as Hartree-Fock wavefunctions occupying crystal sites. The method has been widely tested and applied to transition metal and heavy metal impurities in ionic hosts.[2] In this seminar, results in the study of the structure and spectroscopy of U3+ and Ce3+ doped in Cs2NaYCl6 crystals will be presented, as well as the effect of high pressures in these properties.[3] [1] L. Seijo and Z. Barandiarán, in Computational Chemistry: Reviews of Current Trends, edited by J. Leszczynski (World Scienti.c, Singapore 1999), vol. 4, pag. 55. [2] L. Seijo and Z. Barandiarán, J. Chem. Phys. 89, 5739 (1988); L. Seijo and Z. Barandiarán, J. Chem. Phys. 115, 5554 (2001); J. L. Pascual, Z. Barandiarán, and L. Seijo J. Chem. Phys. 124, 124315 (2006). [3] F. Ruipérez, Z. Barandiarán, and L. Seijo, J. Chem. Phys. 122, 234507 (2005); F. Ruipérez, Z. Baran­diarán, and L. Seijo, J. Chem. Phys. 127 144712 (2007).