Fixed node diffusion Monte Carlo (DMC) has been performed on a test set of forward and reverse barrier heights for 19 non-hydrogen-transfer reactions, and the nodal error has been assessed. The DMC results are robust to changes in the nodal surface, as assessed by using different mean-field techniques to generate single determinant wave functions. Using these single determinant nodal surfaces, DMC results in errors of 1.5(5) kcal/mol on barrier heights. Using the large data set of DMC energies, we attempted to find good descriptors of the fixed node error. It does not correlate with a number of descriptors including change in density, but does correlate with the gap between the highest occupied and lowest unoccupied orbital energies in the mean-field calculation.
@article{arxiv.1611.07860,
title = {Accurate barrier heights using diffusion Monte Carlo},
author = {Kittithat Krongchon and Brian Busemeyer and Lucas K. Wagner},
journal= {arXiv preprint arXiv:1611.07860},
year = {2017}
}