  Accurately modeling gas-surface collision dynamics presents a great challenge
for theory, especially in the low energy (or temperature) regime where quantum
effects are important. Here, a path integral based non-equilibrium ring polymer
molecular dynamics (NE-RPMD) approach is adapted to calculate dissociative
initial sticking probabilities (S0) of H2 on Cu(111) and D2O on Ni(111),
revealing distinct quantum nature in the two benchmark surface reactions.
NE-RPMD successfully captures quantum tunneling in H2 dissociation at very low
energies, where the quasi-classical trajectory (QCT) method suddenly fails.
Additionally, QCT substantially overestimates S0 of D2O due to severe zero
point energy (ZPE) leakage, even at collision energies higher than the
ZPE-corrected barrier. Immune to such a problem, NE-RPMD predicts S0 values of
D2O in much improved agreement with the benchmark results obtained by the
accurate but expensive quantum wavepacket method. Our results suggest NE-RPMD
as a promising approach to model quantum effects in gas-surface reactions.
