Prof. Dr. Reinhart Ahlrichs

Theoretical Chemistry

Prof. Reinhart Ahlrichs

Research in the Theoretical Chemistry group is focussed on the development of the program TURBOMOLE and the application of computational methods to treat properties of molecules or clusters. Our theoretical investigations typically deal with problems of current scientific or industrial interest. Emphasis has recently shifted to the treatment of nano-sized clusters in connection with the "Center for Functional Nanostructures" (CFN), which is a major research effort supported by the DFG and the University of Karlsruhe. Reinhart Ahlrichs also heads a research group at the " Institute for Nanotechnology" at the Forschungszentrum Karlsruhe. The participation in the CFN as well as in two SFBs (Sonderforschungsbereiche) has lead to close cooperations with groups in inorganic and physical chemistry as well as in physics.

TURBOMOLE

TURBOMOLE [1-7,9] includes a series of programs to compute and analyze the electronic structure of molecules by quantum chemistry procedures, such as HF, MP2, or DFT. Especially designed for use on UNIX workstations and Linux-PCs, TURBOMOLE is being used worldwide as shown by about 4000 citations of publications describing its features. The widespread use results mainly from an outstanding efficiency: molecular clusters with a few hundred atoms can be computed on high-end PCs. Another reason for the popularity of TURBOMOLE is its functionality, which offers the treatment of various molecular properties: structure (bond distances and angles), electronic excitations, infrared and Raman spectra, circular dichroism, NMR chemical shifts, etc.

Karlsruhe basis sets

We have determined carefully optimized CGTO basis sets [2,3,10], which combine consistent accuracy and efficiency across the periodic table and are therefore supported by most quantum chemistry programs. All-electron basis sets are available for atoms H to Xe, and additionally for K to At in connection with ECPs. The basis sets are of split valence (SV) and triple zeta valence (TZV) type, augumented by polarization functions they yield SVP up to TZVPP. Basis sets of quadruple zeta quality are soon made available.

Demonstrative applications

Recent applications include the treatment of clusters Aln (n up to 153) [8] and Mgn (up to n = 309) [13], ligand-free semiconductor clusters (CdSe)n, up to n = 99 [14], ligand-stabilized clusters Cu32As10*Ligands and Te26Se12*Ligands [11], circular dichroism [12] as well as some Fullerenes [15].


Cohesive energy of Mg clusters.
Figure 1. The computed cohesive energy of clusters of Al and selected structures [8].





Figure 2. The structure of a mixed valence compuond Cu26Te12(PEt2Ph)12 (without the organic ligands). The calculations show that the additional electron pair (beyond Cu+ and Te2-) is delocalized and not localized in the central Cu6 octahedron.

Selected publications of the Theoretical Chemistry Group

  1. "Electronic Structure Calculations on Workstation Computers: the Program System TURBOMOLE ", R. Ahlrichs, M. Bär, M. Häser, H. Horn and Ch. Kölmel, Chem. Phys. Letters 162 (1989) 165.
  2. "Fully optimized contracted Gaussian basis sets for atoms Li to Kr", A. Schäfer, H. Horn, R. Ahlrichs, J. Chem. Phys. 97 (1992) 2571.
  3. "Fully optimized contracted Gaussian basis sets of triple zeta valence quiality for atoms Li to Kr", A. Schäfer, C. Huber, R. Ahlrichs, J. Chem. Phys. 100 (1994) 5829.
  4. "Efficient molecular numerical integration schemes", O. Treutler and R. Ahlrichs, J. Chem. Phys. 102 (1995) 346.
  5. "Auxiliary basis sets to approximate Coulomb potentials", K. Eichkorn, O. Treutler, H. Öhm, M. Häser and R. Ahlrichs, Chem. Phys. Letters 242 (1995) 652.
  6. "Auxiliary basis sets for main row atoms and transition metals and their use to approximate Coulomb potentials", K. Eichkorn, F. Weigend, O. Treutler, R. Ahlrichs, Theor. Chem. Acc. 97 (1997) 119-124.
  7. "RI-MP2: optimized auxiliary basis sets and demonstration of efficiency", F. Weigend, M. Häser, H. Patzelt, R. Ahlrichs, Chem. Phys. Letters 294 (1998) 143-152.
  8. "Clusters of Aluminium, a density functional study", R. Ahlrichs, S. D. Elliott, Phys. Chem. Chem. Phys. 1 (1999) 13-21.
  9. "Geometry optimization in generalized natural internal coordinates", M. von Arnim, R. Ahlrichs, J. Chem. Phys. 111 (1999) 9183.
  10. "Contracted all-electron Gaussian basis sets for Rb to Xe", R. Ahlrichs, K. May, Phys. Chem. Chem. Phys. 2 (2000) 943-945.
  11. "Synthesis, Crystal Structure, and Binding Properties of the Mixed Valence Clusters [Cu32As30(dppm)8] and [Cu26Te12(PEt2Ph)12]", R. Ahlrichs, J. Besinger, A. Eichhöfer, D. Fenske, A. Gbureck, Angew. Chem. Int. Ed. 39 (2000) 3929-3933.
  12. "Circular Dichroism of Helicenes Investigated by Time-Dependent Density Functional Theory", F. Furche, R. Ahlrichs, C. Wachsmann, E. Weber, A. Sobanski, F. Vögtle, S. Grimme, J. Am. Chem. Soc. 122 (2000) 1717-1724.
  13. "Theoretical Study of Clusters of Magnesium", A. Köhn, F. Weigend, R. Ahlrichs, Phys. Chem. Chem. Phys. 3 (2001) 711-719 .
  14. "Theoretical studies of ligand-free cadmium selenide and related semiconductor clusters", P. Deglmann, R. Ahlrichs, K. Tsereteli, J. Chem. Phys., 116 (2002) 1585-1587.
  15. "Absolute Configuration of D2-Symmetric Fullerene C84", F. Furche, R. Ahlrichs, J. Am. Chem. Soc. 124 (2002) 3804-3805.

Further information

In the period 1990-2000 18 diploma and 20 PhD students have completed their theses. Results have been published in about 100 papers. This work has been supported by the DFG through SFB 195, the BMBF, a EU project, and the Chemical Industry.

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