Stress Test for Quantum Dynamics Approximations: Deep Tunneling in the Muonium Exchange Reaction D + HMu → DMu + H.
Quantum effects play a crucial role in chemical reactions involving light atoms at low temperatures, especially when a light particle is exchanged between two heavier partners. Different theoretical methodologies have been developed in the last decades attempting to describe zero-point energy and tunneling effects without abandoning a classical or semiclassical framework. In this work, we have chosen the D + HMu → DMu + H reaction as a stress test system for three well-established methods: two representative versions of transition state theory (TST), canonical variational theory and semiclassical instanton, and ring polymer molecular dynamics (RPMD). These calculations will be compared with accurate quantum mechanical results. Despite its apparent simplicity, the exchange of the extremely light muonium atom (0.114 u) becomes a most challenging reaction for conventional methods. The main result of this work is that RPMD provides an overall better performance than TST-based methods for such a demanding reaction. RPMD might well turn out to be a useful tool beyond TST applicability.
†Departamento de Quı́mica Fı́sica I, Facultad de CC. Quı́micas, Universidad Complutense de Madrid, 28040 Madrid, Spain.
Ricardo
R
Pérez de Tudela
‡Computation-based Science and Technology Research Center, Cyprus Institute, 20 Kavafi Str., Nicosia 2121, Cyprus.|∥Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Yury V
YV
Suleimanov
¶Institut für Theoretische Physik und Interdisziplinäres Zentrum für Molekulare Materialien, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany.
Jeremy O
JO
Richardson
§Departamento de Quı́mica y Bioquı́mica, ETS Ingenieros de Montes, Universidad Politécnica, 28040 Madrid, Spain.
Vicente
V
Sáez Rábanos
∥Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
William H
WH
Green
†Departamento de Quı́mica Fı́sica I, Facultad de CC. Quı́micas, Universidad Complutense de Madrid, 28040 Madrid, Spain.
F J
FJ
Aoiz
chemical kinetics; gas-phase reactions; isotope effect; molecular simulations; reaction dynamics