QUANTUM DESCRIPTION OF LARGE AMPLITUDE MOTION
IN HYDROGEN BONDED SYSTEMS
IVANA
MATANOVIĆ1, NAĐA DOLIĆ1, OLIVER KÜHN2
1 R. Boković Institute, Department of
Physical Chemistry, Bijenička 54, 10 000 Zagreb, Croatia
2 Institute for Chemistry and Biochemistry, Free
University Berlin, Takustr. 3, D-14195 Berlin, Germany
We present two quantum methods capable of
describing the Large Amplitude internal motion (LAM) in H-bonded Systems. The
solution of the multidimensional Schrödinger equation is achieved both in localized
and collective LAM coordinates. First approach uses a localized internal
coordinates representation of the Hamiltonian in which the coordinate
dependence of the Wilson G-matrix needs to be taken into account [1]. The second
approach is based on the definition of the minimum energy path (MEP). In this
approach the collective LAM coordinates are constructed as a linear combination
of a few critical geometries on the MEP in such a way to best reproduce the
system geometries and energetics on the MEP [2,3]. The remaining orthogonal degrees of freedom are linearized and the dynamics is treated within the Reaction
Surface Hamiltonian approach.
The methods were applied to H-transfer
reactions in acetylacetone (ACAC) and the formic acid
dimer (FAD). Tunnelling
splitting for the zero-point level and for the lowest vibrationaly
excited level of the antisymmetric C-O stretch
vibration in FAD were calculated and confronted with the high resolution
experiments by Madeja and Havenith
[4].
1. I. Matanović, N. Dolić, J. Phys.
Chem., 109, 4184 (2005)
2. K. Giese, O. Kühn, J. Chem. Phys. 123,
074308 (2005)
3. I. Matanović, N. Dolić, O. Kühn,
in preparation
4. F. Madeja, M. Havenith, J. Chem. Phys, 117,
7162 (2002)