These two volumes collect forty-four selected papers from the scientific contributions presented at the Third European Workshop on Quantum Systems in Chemistry and Physics, held in Granada (Spain), April 19-22, 1998. Ninety-nine scientists from Bulgaria, Columbia, Cuba, Denmark, Finland, France, Germany, Hungary, Israel, Italy, Mexico, Netherlands, Norway, Poland, Russia, Slovakia, Spain, Sweden, United Ki- dom, Uruguay and Venezuela attended the workshop, discussing the state of the art, new trends, and future evolution of the methods and applications. The workshop took place at the 'Los Alixares' Hotel, where 45 lectures were given by prominent members of the scientific community; in addition, 49 posters were presented in two very animated sessions. The success of this workshop is due, without doubt, to the excellent tradition initiated at the previous workshops, organised by Prof. R. McWeeny in San Miniato, Pisa (Italy), 1996, and by Prof. S. Wilson in Oxford (United Kingdom), 1997. These workshops create occasions for meetings and disc- sions on the current state of the art, emerging methods and applications and new trends in this area of science. The three meetings were sponsored and partially supported by the European Union (EU) in the frame of the Cooperation in Science and Technology (COST) chemistry actions.

Inhalt

Preface. 1. Density Matrices and Density Functionals. 3-Body Correlation Effects in Third Order Reduced Density Matrices; C. Valdemoro, et al. 2. Electron Correlation Effects. Ab Initio Summation Over States/CI Singles for Static and Dynamic First Hyperpolarizabilities of Small Molecules; M. Spassova, et al. Comparing (SC)2CAS-SDCI and Externally Corrected CCSD Methods; G. Peris, J.P. Malrieu. The Size-Consistent Self-Consistent SDCI Method for Excited States and Ionization Potentials; J. Pitarch-Ruiz, et al. Influence of Electron Correlation on the Electronic Structure of Superconducting Y-Ceramics; I.G. Kaplan, et al. 3. Relativistic Formulations. Perspectives in Relativistic Thomas-Fermi Calculations for Atomic Systems; I. Porras, A. Moya. Expectation Values for Ground State Atoms from a Modified Thomas-Fermi-Diract Approach; A. Moya, I. Porras. Relativisitic oscillator strengths for excited-state transitions in halogen atoms. Regularities; C. Lavin, et al. Extension of the Relativistic Quantum Defect Orbital Method to the Tratment of Many-valence Electron Atoms. Atomic Transition in Ar II; I. Martíin, et al. 4. Valence Theory. 5. Nuclear Motions. The Effect of the Pseudopotential on the Torsional Energy Levels of Hydrogen Peroxide and Deuterium Peroxide; M.L. Senent, Y.G. Smeyers. 6. Response Theory. Duality in Two-ways Interferometers: The Symmetric Quanton-Detecton System; J. Martínez-Linares, D.A. Harmin. Atomic Resonances in External Field; R. González-Ferez, W. Scheweizer. 7. Condensed Matter. Diffusion Monte Carlo Calculations of Quasibound States of Rare Gas-halogen Clusters: a Diabatic Approach; G.García-Rizo, et al. 8. Reactive Collisions and Chemical reactions. Electro-nuclear Quantum Mechanics Beyond the Born-Oppenheimer Approximation. Towards a Quantum Electronic Theory of Chemical Reaction Mechanisms. 9. Computational Chemistry and Physics. N-O and P-O Bond Nature in Hypervalent Compounds. Is Bader Analisys Basis Set and Geometry Independent? J.A. Dobado, et al. A Theoretical Study of the Radical Addition to the Xylenes; V.-H. Uc, et al. Theoretical Study of the Proton Affinities of Some Substituted Derivatives of Histamine and Homologous Compounds. Structure-Activity Relationships.