Nuclear quantum effects in chemical reactions via higher-order path-integral calculations

• Published in: Chemical physics Vol. 450-451; pp. 95 - 101
• Main Authors: Engel, Hamutal, Eitan, Reuven, Azuri, Asaf, Major, Dan Thomas
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2015
• Subjects: Forward corrector algorithm; Nuclear quantum effects; Path integral; Tunneling; Tunneling; Forward corrector algorithm; Path integral; Nuclear quantum effects
• ISSN: 0301-0104
• DOI: 10.1016/j.chemphys.2015.01.001

[Display omitted] •The study presents path-integral calculations for chemical reactions.•The path-integrals use higher-order factorizations of the density matrix.•The Eckart potential and the H2+H reaction are used as test cases for the methods.•The Chin higher order factorization enhances QM transmission convergence.•The higher order factorizations enhance eigenvalue and partition function convergence. A practical approach to treat nuclear quantum mechanical effects in simulations of condensed phases, such as enzymes, is via Feynman path integral (PI) formulations. Typically, the standard primitive approximation (PA) is employed in enzymatic PI simulations. Nonetheless, these PI simulations are computationally demanding due to the large number of beads required to obtain converged results. The efficiency of PI simulations may be greatly improved if higher-order factorizations of the density matrix operator are employed. Herein, we compare the results of model calculations obtained employing the standard PA, the improved operator of Takahashi and Imada (TI), and a gradient-based forward corrector algorithm due to Chin (CH). The quantum transmission coefficient is computed for the Eckart potential while the partition functions and rate constant are computed for the H2+H hydrogen transfer reaction. These potentials are simple models for chemical reactions. The study of the different factorization methods reveals that in most cases the higher-order action converges faster than the PA and TI approaches, at a moderate computational cost.