Quantum Mechanical Electronic Structure Calculations with Chemical Accuracy

The theoretical chemist is accustomed to judging the success of a theoretical prediction according to how well it agrees with an experimental measurement. Since the object of theory is the prediction of the results of experiment, that would appear to be an entirely satisfactory state ofaffairs. However, ifit is true that "the underlying physicallaws ... for the whole ofchemistryare ... completely known" (1), thenit shouldbepossible,atleastinprinciple, topredict theresults of experiment moreaccurately than they canbe measured. Ifthe theoreticalchemist could obtain exact solutions ofthe Schrodinger equation for many-body systems, then the experimental chemist would soon become accustomed to judging the success ofan experimental measurement by how well it agrees with a theoretical prediction. In fact, it is now possible to obtainexact solutions ofthe Schrodinger equation for systems ofa few electrons(2-8). These systems include the molecular ion Ht, the molecule H , the reaction intermediate H-H-H, the unstable pair H-He, the 2 stable dimer He2' and the trimer He3. The quantum Monte Carlo method used in solving the time-independent Schrodinger equation for these systems is exact in that it requires no physical or mathematical assumptions beyond those of the Schrodinger equation. As in most Monte Carlo methods there is a statistical or sampling error which is readily estimated.

Klappentext

The principal focus of this volume is to illustrate the level of accuracy currently achievable by ab initio quantum chemical calculations. While new developments in theory are discussed to some extent, the major emphasis is on a comparison of calculated properties with experiment. This focus is similar to the one taken in a book, Comparison of Ab Initio Quantum Chemistry with Experiment for Small Molecules, edited by Rodney Bartlett (Reidel, 1984). However, the phenomenal improvement in both theoretical methods and computer architecture have made it possible to obtain accurate results for rather large molecular systems. This is perhaps best illustrated in this volume by the chapter entitled `Spectroscopy of Large Organic Molecules' by Bjorn Roos and coworkers. For example, the electronic spectra of the nucleic acid base monomer structures shown on the front cover have been obtained using a fully correlated ab initio study. For researchers, teachers and students in chemistry and physics.

Inhalt
1 Exact Quantum Chemistry by Monte Carlo Methods.- 47 Achieving Chemical Accuracy with Coupled-Cluster Theory.- 109 Magnetic Hyperfine Coupling Constants in Free Radicals.- 139 Calculation of Accurate Bond Energies, Electron Affinities, and Ionization Energies.- 173 Accurate Theoretical Studies of Small Elemental Clusters.- Electronic Spectroscopy of Diatomic Molecules.- 261 Theoretical Spectoscopy of Small Molecules: Ab Initio Investigations of Vibronic Structure, Spin-Orbit Splittings and Magnetic Hyperfine Effects in the Electronic Spectra of Triatomic Molecules.- Theoretical Studies of the Electronic Spectra of Organic Molecules.