Quasiclassical simulations based on cluster models reveal vibration-facilitated roaming in the isomerization of CO adsorbed on NaCl


The desire to better understand the quantum nature of isomerization led to recent experimental observations of the vibrationally induced isomerization of OC–NaCl(100) to CO–NaCl(100). To investigate the mechanism of this isomerization, we performed dynamics calculations using finite (CO–NaCl)n cluster models. We constructed new potential energy surfaces for CO–NaCl and CO–CO interactions using high-level ab initio data and report key properties of the bare CO–NaCl potential energy surface, which show much in common with the experiment. We investigated the isomerization dynamics using several cluster models and, in all cases, isomerization was seen for highly excited CO vibrational states, in agreement with experiments. A detailed examination of the reaction trajectories indicates that isomerization occurs when the distance between CO and NaCl is larger than the distance at the conventional isomerization saddle point, which is a strong indicator of ‘roaming’.

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Fig. 1: Structures of the C-down and O-down minima from the average CO–NaCl potential.
Fig. 2: Depictions of the central CO for C-down and O-down isomers for the cluster with 13 COs.
Fig. 3: One-dimensional unrelaxed potential cuts for isomerization.
Fig. 4: Contour plots for the large cluster PES of the central CO.
Fig. 5: Histogram of the distribution of z, the distance above the surface, at which isomerization occurs.
Fig. 6: Signature of roaming dynamics.

Data availability

All the data shown here are available in the Supplementary Information. Source data are provided with this paper.

Code availability

The potentials reported in the paper are available in compressed folders as Supplementary Information.


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J.M.B. and H.G. thank the Alexander von Humboldt Foundation for Humboldt Research Awards. In addition, J.M.B. thanks NASA (80NSSC20K0360) for financial support and H.G. thanks the National Science Foundation (CHE-1462109 and CHE-1951328) for financial support. We thank J. Lau and A. Wodtke for extensive discussions.

Author information




A.N. performed the dynamics calculations, developed the CO–NaCl potential and cluster potential, refitted the CO–CO potential and helped write the paper and prepared most of the figures. P.Z. performed DFT calculations of energies of the CO–NaCl stationary points. J.C. performed electronic structure calculations of the CO–CO interaction. H.G. helped conceive the research, helped writing the paper and supervised the creation of the CO–CO electronic energy dataset. J.M.B. conceived the research, wrote the paper and supervised the dynamics calculations.

Corresponding author

Correspondence to Joel M. Bowman.

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The authors declare no competing interests.

Additional information

Peer review information Nature Chemistry thanks Jochen Vogt and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–14, and Tables 1–9.

Supplementary Video 1

QCT Trajectory Animation.

Supplementary Software 1

All three PES Software. ‘CO_CO_Int’ folder contains CO-CO interaction PES; ‘CO_MRCI’ folder contains isolated CO PES; and ‘NaCl_CO_Int’ folder contains NaCl-CO interaction PES.

Supplementary Data 1

Source data for the figures within the Supplementary Information file.

Source data

Source Data Fig. 3

Source data for Figure 3.

Source Data Fig. 4

Source data for Figure 4.

Source Data Fig. 5

Source data for Figure 5 .

Source Data Fig. 6

Source data for Figure 6.

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Nandi, A., Zhang, P., Chen, J. et al. Quasiclassical simulations based on cluster models reveal vibration-facilitated roaming in the isomerization of CO adsorbed on NaCl. Nat. Chem. (2021). https://doi.org/10.1038/s41557-020-00612-y

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