Major research areas

Many-Electron Sturmian functions as an Alternative to the SCF-CI Method (John Avery)

Methods have been developed for solving the many-electron Schrödinger equation directly, without the use of the self-consistent-field approximation. These methods make use of many-electron Sturmian basis sets. The functions in such a set are solutions to a zeroth-order many-electron Schrödinger equation with a weighted "basis potential" V₀, the weighting factors being chosen in such a way as to make all the members of the basis set correspond to the same energy regardless of their quantum numbers. When the basis potential is chosen to be the actual nuclear attraction potential of a many-electron system, this representation of the true wave function converges rapidly. Pilot studies applying the generalized Sturmian method to calculation of the wave functions and properties of atoms and molecules have yielded accurate results. It is planned to extend these studies and to construct generally applicable computer programs for implementing the method.

Aage E. Hansen

Theoretical developments and computational and graphical studies of molecular electric and magnetic properties as tools for theoretical structure chemistry.

Special interests : Computational studies of magnetic shieldings as tools for questions concerning aromaticity and antiaromaticity. Theoretical developments and computations of the rotatory strength tensors that determine the circular dichroism spectra of oriented molecular systems. Development and application of graphical methods for the display of molecular response properties.

Molecular Many-Electron Theory (Sten Rettrup)

Methods for calculating electron correlation in many-electron molecules. Connected to the development of such methods particular interest is paid to a series of topics indicated by the following keywords:

• Optimization of virtual orbital spaces for the calculation of electronic properties of excited states.
  
• Graphical methods for the representation and enumeration of many-electron states.
  
• Spin-free methods for the development of ab initio configuration interaction (CI) programmes.
  
• Diagonalization and solution of very large matrix eigenvalue problems and linear equations.
  
• Parallellization of quantum chemistry programmes on distributed memory machines.
  
• Valence bond methods for studying the electronic structure of molecules.
  
• Symmetric group algebras and its application in many-electron theory.
  

Theory and Calculations of Molecular Electric and Magnetic Properties (Stephan P. A. Sauer)

Theoretical investigations of the interaction between molecules and external or internal static electromagnetic fields as well as electromagnetic radiation. These interactions are commonly expressed in terms of molecular properties like the chemical shifts and nuclear spin-spin coupling constants in an NMR spectrum, the electronic excitation energies and oscillator strengths in a UV spectrum, linear and non-linear optical properties (polarizability, hyperpolarizability), magnetizability, rotational and vibrational g-factor, spin rotation constant and many more.

The research activities consist both of the development of new or improved quantum chemical methods and programs for the calculation of these properties and actual applications of these methods to current chemical problems. The quantum chemical methods used so far are based on the non-relativistic Schrödinger equation and treat electron correlation by perturbation theory. In particular the second order polarization propagator approximation (SOPPA) has been applied. As a second order method like MP2, SOPPA constitutes a good compromise between accuracy and computational cost, which makes it particularly well suited for the larger and chemically relevant systems. Typical applications are concerned with the interpretation and explanation of experimental findings (like unexpected isotope shifts in NMR parameters) in terms of molecular properties and individual contributions to them as well as with the prediction or modelling of electromagnetic properties of materials. In both cases the goal is to help the experimentally working chemists or material scientists.

Current projects include :
Systematic comparison of the performance of SOPPA and SOPPA(CCSD) with other methods; development of an atomic integral direct SOPPA program; implementation of an SOPPA solvent reaction field model; development of small basis sets for spin-spin coupling constants; investigation of the effects of nuclear motion on molecular properties; calculation of electronic spectra of azobenzene dyes used in optical data storage materials; exciton binding energy and bandgap of polyacetylene; nonadiabatic rotational and vibrational effects in rotational spectra of diatomic molecules.

	Kemisk Laboratorium IV	Tel: (+45) 35 32 02 68
	Universitetsparken 5	Fax: (+45) 35 32 02 99
	DK-2100 Copenhagen Ø, Denmark	E-mail: sauer@kiku.dk

visitors since 07-02-2002

Last updated 07-02-2002 Please send comments and corrections to sauer@kiku.dk