Name: Robert Hünerbein
Diploma / M.Sc degree: Westfälische Wilhelms-Universität Münster, Germany
(September 2006)

PhD Project: DFT-Calculations on Organic Molecules

Abstract of Research Project

The development of modern chemistry at the borderline between biology and physics requires a deep theoretical understanding of matter at a microscopic level.For major parts of chemistry, this description can be achieved with very good accuracy in the framework of non-relativistic quantum mechanics and applying the usual Born-Oppenheimer approximation. Today, multiple and well established approximate methods for the solution of the corresponding electronic Schrödinger equation are available. In principle, these methods allow the calculation of all experimentally relevant properties of atoms, molecules, clusters and solids. This is the basic reason why quantum chemistry has settled within the last 10-20 years into a widely accepted position beside the older chemical disciplines.

Traditional ab inito methods to solve the time-independent electronic Schrödinger equation are usually based on an expansion of the wave function (WF) in a finite basis of suitable, analytically known functions. In the standard approach, the problem is first transformed into a mean-field form (Hartree-Fock method) and the remaining correlation energy is calculated with an expansion in Slater determinants. The accurate consideration of these electron correlation (many-particle) effects is indispensable to reach what is called "chemical accuracy" and thus, still a major topic of quantum chemical research. Although the systematic approach of the WF based methods yields asymptotically an exact solution of the Schrödinger equation, in practice severe restrictions with respect to the size of the investigated systems have to be obeyed. In recent years, Kohn-Sham density functional theory (DFT), which tries to solve the correlation problem by an effective one-particle potential (exchange-correlation functional) depending only on the electron density, has emerged as a cheap alternative to the traditional WF based methods. Although DFT methods yield excellent results for a wide range of molecular properties and furthermore can be applied to systems consisting of hundreds of atoms, important exceptions and problematic cases (weak interactions, reaction barriers, charge-transfer systems, biradicals) are known. The further development of density functionals by comparative calculations with highly correlated WF methods is therefore an important research topic in quantum chemistry. The application and improvement of DFT methods will be the topic of my work.


Publications

H. Lange, R. Hünerbein, B. Wibbeling, R. Fröhlich , S. Grimme, D. Hoppe
Comprehensive experimental and theoretical studies of configurationally labile epimeric diamine complexes of alpha-lithiated benzyl carbamates
Synthesis 18 (2008), 2905-2918.

R. Hünerbein, S. Grimme
Time-dependent density functional study of excimers and exciplexes of organic molecules
Chem. Phys. 343 (2008), 362-371.

H. Lange, R. Hünerbein, R. Fröhlich, S. Grimme, D. Hoppe
Configurationally labile lithiated O-benzyl carbamates: Application in asymmetric synthesis and quantum chemical investigations on the equilibrium of diastereomers
Chem. Asian. J. 3 (2007), 78-87.

T. Glaser, M. Heidemeier, J. B. H. Strautmann, H. Bögge, A. Stammler, E. Krickemeyer, R. Hünerbein, S. Grimme, E. Bothe, E. Bill
Trinuclear copper complexes with triplesalen ligands: geometric and electronic effects on ferromagnetic coupling via the spin-polarization mechanism
Chem. Eur. J. 13 (2007), 9191-9206.

M. Zwijnenburg , R. Hünerbein, R. Bell
A computational study into the (tetrahedral) distortion of TX₂ alpha-quartz materials: The effect of changing the chemical composition away from SiO₂
J. Solid. State. Chem. 179 (2006), 3429-3436.


Robert Hünerbein
eMail: Robert Hünerbein