Bokdam, M and Lahnsteiner, J and Sarma, DD (2021) Exploring Librational Pathways with on-the-Fly Machine-Learning Force Fields: Methylammonium Molecules in MAPbX3(X = I, Br, Cl) Perovskites. In: Journal of Physical Chemistry C, 125 (38). pp. 21077-21086.
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Abstract
Two seemingly similar crystal structures of the low-temperature (∼100 K) MAPbX3(X = I, Br, Cl) perovskites, but with different relative methylammonium (MA) ordering, have appeared as representatives of this orthorhombic phase. Distinguishing them by X-ray diffraction experiments is difficult, and conventional first-principles-based molecular dynamics approaches are often too computationally intensive to be feasible. Therefore, to determine the thermodynamically stable structure, we use a recently introduced on-the-fly machine-learning force field method, which reduces the computation time from years to days. The molecules exhibit a large degree of anharmonic motion depending on temperature: that is, rattling, twisting, and tumbling. We observe the crystal’s “librational pathways” while slowly heating it in isothermal-isobaric simulations. Marked differences in the thermal evolution of structural parameters allow us to determine the real structure of the system via a comparison with experimentally determined crystal structures.
| Item Type: | Journal Article |
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| Publication: | Journal of Physical Chemistry C |
| Publisher: | American Chemical Society |
| Additional Information: | The copyright for this article belongs to the Authors. |
| Keywords: | Crystal structure; Machine learning; Molecular dynamics; Molecules; Temperature, Crystals structures; Dynamic approaches; First principles; Forcefields; Lows-temperatures; Machine-learning; Orthorhombic phase; Stable structures; Thermodynamically stable; X- ray diffractions, Perovskite |
| Department/Centre: | Division of Chemical Sciences > Solid State & Structural Chemistry Unit |
| Date Deposited: | 06 Jun 2023 08:42 |
| Last Modified: | 06 Jun 2023 08:42 |
| URI: | https://eprints.iisc.ac.in/id/eprint/81773 |
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