Efficient partitioning technique for computing the dynamics of intramolecular processes: radiationless transitions in pyrazine.
An efficient QP partitioning algorithm to compute the eigenvalues, eigenvectors, and the dynamics of large molecular systems of a particular type is presented. Compared to straightforward diagonalization, the algorithm displays favorable scaling (proportional to N(T)2) as a function of N(T), the size of the Hamiltonian matrix. In addition, the algorithm is trivially parallelizable, necessitating no "cross-talk" between nodes, thus enjoying the full linear speedup of parallelization. Moreover, the method requires very modest storage space, even for extremely large matrices. The method has also been enhanced through the development of a coarse-grained approximation, enabling an increase of the basis set size to unprecedented levels (10(8)-10(10) in the current application). The QP algorithm is applied to the dynamics of electronic internal conversion in a 24 vibrational-mode model of pyrazine. A performance comparison with other dynamical methods is presented, along with results for the decay dynamics of pyrazine and a discussion of resonance line shapes.
Christopher
P S
PS
Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
Shapiro
Moshe
M
Brumer
Paul
P