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BP: Fachverband Biologische Physik

BP 15: Proteins II

BP 15.9: Talk

Wednesday, March 28, 2012, 17:15–17:30, H 1058

Hierarchical Expansion of the Kinetic Energy Operator in Curvilinear Coordinates — Daniel Strobusch and •Christoph Scheurer — Lehrstuhl für Theoretische Chemie, TU München, Lichtenbergstr. 4, 85748 Garching, Germany

Multidimensional nonlinear IR experiments provide detailed dynamical information about peptides on short timescales. The interpretation of these spectra relies heavily on theoretical simulations of anharmonic vibrational systems. A powerful approach to calculate anharmonic vibrational spectra is the vibrational self-consistent field method (VSCF) and its configuration interaction extension (VCI).

Couplings and correlation between different modes can be reduced by employing curvilinear coordinates [1], which is of utmost importance for larger systems. However, these coordinates at the same time introduce a more complex form of the kinetic energy operator T, which has been known for a long time. Its evaluation is involved though, with coordinate dependent reduced masses and kinematic couplings.

A new systematic hierarchical expansion of T is presented, which allows us to judge the quality of simpler ad-hoc approximations [2]. VSCF and VCI calculations for small model systems were performed and the influence of different terms in the kinetic energy operator was studied in detail to allow for efficient approximations.

[1] M. Bounouar and Ch. Scheurer, Chem. Phys. 347 (2008), 194
[2] D. Strobusch and Ch. Scheurer, J. Chem. Phys. 135 (2011), 124102; ibid., 144101