Professor

Centre for Theoretical and Computational Chemistry
Department of Chemistry
University of Oslo

Mailing address:

Department of Chemistry
University of Oslo
P. O. Box 1033
Blindern
N-0315 Oslo

Research interests

• The development of methods for the calculation of molecular electronic structure from first principles, with emphasis on high accuracy (coupled-cluster theory) and large systems (density-functional theory).
• The development of methods for the calculation of the response of molecular systems to internal and external perturbations such as nuclear displacements and applied electromagnetic fields (molecular structure, spectroscopic constants, reactivity).
  
• Molecular dynamics.
  
• Benchmarking of quantum-chemistry methods, including convergence studies and extrapolation techniques. The application of such methods to problems of chemical interest.

Selected publications

• T. U. Helgaker and J. Almlöf, A second-quantization approach to the analytical evaluation of response properties for perturbation-dependent basis sets, Int. J. Quantum Chem. 26, 275–291 (1984)
  
• H. Koch, H. J. Aa. Jensen, P. Jørgensen, T. Helgaker, G. E. Scuseria, and H. F. Schaefer, Coupled cluster energy derivatives. Analytic Hessian for the closed-shell coupled cluster singles and doubles wave function: Theory and applications, J. Chem. Phys. 92, 4924–4940 (1990)
  
• H. Koch, H. J. Aa. Jensen, P. Jørgensen, and T. Helgaker, Excitation energies from the coupled-cluster singles and doubles linear response function (CCSDLR). Applications to Be, CH+, CO, and H2O, J. Chem. Phys. 93, 3345–3350 (1990)
  
• T. Helgaker, E. Uggerud, and H. J. Aa. Jensen, Integration of the classical equations of motion on ab initio molecular potential energy surfaces using gradients and Hessians: application to translational energy release upon fragmentation, Chem. Phys. Letters 173, 145–150 (1990)
  
• K. Ruud, T. Helgaker, R. Kobayashi, P. Jørgensen, K. L. Bak, and H. J. Aa. Jensen, Multiconfigurational self-consistent field calculations of nuclear shieldings using London atomic orbitals, J. Chem. Phys. 100, 8178–8185 (1994)
  
• H. Koch, A. Sánchez de Merás, T. Helgaker, and O. Christiansen, The integral-direct coupled cluster singles and doubles model, J. Chem. Phys. 104, 4157–4165 (1996)
  
• T. Helgaker, W. Klopper, H. Koch, and J. Noga, [185] Basis-set convergence of correlated calculations on water, J. Chem. Phys. 106, 9639–9646 (1997)
• T. Helgaker, J. Gauss, P. Jørgensen, and J. Olsen, [122] The prediction of molecular equilibrium structures by the standard electronic wave functions, J. Chem. Phys. 106, 6430–6440 (1997)
  
• T. Helgaker, M. Jaszunski, K. Ruud, Ab initio methods for the calculation of NMR shielding and indirect spin–spin coupling constants, Chem. Rev. 99, 293–352 (1999)
  
• T. Helgaker, P. Jørgensen, and J. Olsen, Molecular Electronic-Structure Theory, Wiley, Chichester, 2000.
  
• T. Helgaker, H. Larsen, J. Olsen, and P. Jørgensen, Direct optimization of the AO density matrix in Hartree–Fock and Kohn–Sham theories, Chem. Phys. Lett. 327, 397–403 (2000)
  
• T. Helgaker, M. Watson, and N. C. Handy, Analytical calculation of nuclear magnetic resonance indirect spin–spin coupling constants at the generalized gradient approximation and hybrid levels of density-functional theory J. Chem. Phys. 113, 9402–9409 (2000)
  
• K. Ruud and T. Helgaker, Optical rotation studied by density-functional and coupled-cluster methods, Chem. Phys. Lett. 352, 533–539 (2002)
• T. Saue and T. Helgaker Four-component relativistic Kohn–Sham theory, J. Comput. Chem. 23, 814–823 (2002)
  
• M. A. Watson, P. Salek, P. Macak, M. Jaszunski, and T. Helgaker, The calculation of indirect nuclear spin–spin coupling constants in large molecules, Chem. Eur. J. 10, 4627–4639 (2004)
  
• L. Thøgersen, J. Olsen, A. Köhn, P. Jørgensen, P. Salek, and T. Helgaker, The trust-region self-consistent field method in Kohn–Sham density-functional theory, J. Chem. Phys. 123, 074103 (2005)
  
• T. Helgaker, A. C. Hennum, and W. Klopper, A second-quantization framework for the unified treatment of relativistic and nonrelativistic molecular perturbations by response theory, J. Chem. Phys. 125, 024102 (2006) 234.
  
• P. Salek, S. Høst, L. Thøgersen, P. Jørgensen, P. Manninen, J. Olsen, B. Jansik, S. Reine, F. Pawlowski, E. Tellgren, and T. Helgaker, A linear-scaling implementation of molecular electronic self-consistent field theory, J. Chem. Phys. 126, 114110 (2007)

Curriculum Vitae

• PDF file