Exploring Configurations of Nanocrystal Ligands Using Machine-Learned Force Fields

Sowa, Jakub K.; Roberts, Sean T.; Rossky, Peter J.

doi:10.1021/acs.jpclett.3c01618

Cited by 1 publication

(4 citation statements)

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“…Lastly, we investigate the geometries adopted by the butyrate ligands during the NVE simulation (and that therefore directly correspond to the observed IR spectrum). We use a method introduced in our previous study . Briefly, for each ligand, we identify its primary lead atom, Pb*, as the lead atom closest to the average position of the two oxygen atoms.…”

Section: Resultsmentioning

confidence: 99%

“…Our work also resolves the apparent inconsistency between the conventional interpretation of the IR spectroscopy of carboxylate-passivated PbS nanocrystals ,− , and previous computational studies on these systems . The former postulated a coexistence of bridging and chelating ligand geometries, while the latter suggested that chelating geometries should not be observed.…”

Section: Discussionmentioning

confidence: 99%

“…Previously, we have shown, using a model acetate-passivated PbS nanocrystal, that IR spectra of small quantum dots can be effectively simulated using molecular dynamics (MD) utilizing machine-learned force fields trained on DFT data. − This approach was demonstrated to circumvent issues associated with alternative methods that make use of analytical force fields, DFT harmonic mode analysis, , or exceedingly computationally intensive ab initio MD (AIMD) simulations …”

Section: Introductionmentioning

confidence: 99%

“…The results of IR spectroscopy on oleate-passivated PbS (and closely related PbSe) nanocrystals have been repeatedly discussed in the literature. ,− , Following the work of Cass et al, it has been generally assumed, primarily due to the broad and highly non-Lorentzian shape of the antisymmetric C–O stretch band, that the observed IR signal indicates coexistence of chelating and bridging oleate geometries. Our earlier simulations of acetate-passivated nanocrystals suggested that chelating geometries should not be observed, in line with prior computational studies of carboxylate-passivated CdSe nanocrystals. , However, our use of short acetate ligands in our prior work prohibited us from making a direct comparison with experiment . The primary aim of this work is, therefore, to resolve this issue by simulating spectra of PbS nanocrystals capped with longer ligands that can also be used experimentally.…”

Section: Introductionmentioning

confidence: 99%

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IR Spectroscopy of Carboxylate-Passivated Semiconducting Nanocrystals: Simulation and Experiment

Sowa,

Cadena,

Mehmood

et al. 2024

J. Phys. Chem. C

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The surfaces of colloidal nanocrystals are frequently passivated with carboxylate ligands that exert significant effects on their optoelectronic properties and chemical stability. The binding geometries of these ligands are often experimentally investigated using vibrational spectroscopy, but the interpretation of the IR signal is usually not trivial. Here, using machine-learning (ML) algorithms trained on DFT data, we simulate an IR spectrum of a lead-rich PbS nanocrystal passivated with butyrate ligands. We obtain good agreement with the experimental signal and demonstrate that the observed line shape stems from a very wide range of "tilted-bridge"-type geometries and does not indicate the coexistence of "bridging" and "chelating" binding modes as has been previously assumed. This work illustrates the limitations of empirical spectrum assignment and demonstrates the effectiveness of ML-driven molecular dynamics simulations in reproducing the IR spectra of nanoscopic systems.

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Section: Resultsmentioning

confidence: 99%