Efficient partitioning technique for computing the dynamics of intramolecular processes:Radiationless transitions in pyrazine

摘要

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(propor.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.