Quantum flux operators and thermal rate constant: Collinear H+H2

The exact quantum formulation of the thermal rate constant, k(T), given by Miller et al. W. H. Miller, J. Chem. Phys. 61, 1823 (1974); W. H. Miller, S. D. Schwartz, and J. W. Tromp, ibid. 79, 4889 (1983) is evaluated in a localized L2 basis (distributed Gaussian basis) for two model problems. In considering the accuracy, feasibility, and computational efficiency of this approach, we demonstrate novel properties of the flux operator, namely the paucity of nonzero eigenvalues. This contributes greatly to the efficiency of the L2 approach. Finally, we show that Lanczos reduction can be used effectively for determining the thermal flux projectors and their time evolution as is required for evaluation of k(T).