Topological Data analysis of Ion Migration Mechanism

R Sato and K Akagi and S Takagi and K Sau and K Kisu and H Li and SI Orimo, JOURNAL OF CHEMICAL PHYSICS, 158, 144116 (2023).

DOI: 10.1063/5.0143387

Topological data analysis based on persistent homology has been applied to the molecular dynamics simulation for the fast ion-conducting phase (a-phase) of AgI to show its effectiveness on the ion migration mechanism analysis. Time-averaged persistence diagrams of a-AgI, which quantitatively record the shape and size of the ring structures in the given atomic configurations, clearly showed the emergence of the four- membered rings formed by two Ag and two I ions at high temperatures. They were identified as common structures during the Ag ion migration. The averaged potential energy change due to the deformation of the four- membered ring during Ag migration agrees well with the activation energy calculated from the conductivity Arrhenius plot. The concerted motion of two Ag ions via the four-membered ring was also successfully extracted from molecular dynamics simulations by our approach, providing new insight into the specific mechanism of the concerted motion.

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