Title: Persistent Homology Metrics Reveal Quantum Fluctuations and Reactive Atoms in Path Integral Dynamics

Abstract

Nuclear quantum effects (NQEs) are known to impact a number of features associated with chemical reactivity and physicochemical properties, particularly for light atoms and at low temperatures. In the imaginary time path integral formalism, each atom is mapped onto a “ring polymer” whose spread is related to the quantum mechanical uncertainty in the particle’s position, i.e., its thermal wavelength. A number of metrics have previously been used to investigate and characterize this spread and explain effects arising from quantum delocalization, zero-point energy, and tunneling. Many of these shape metrics consider just the instantaneous structure of the ring polymers. However, given the significant interest in methods such as centroid molecular dynamics and ring polymer molecular dynamics that link the molecular dynamics of these ring polymers to real time properties, there exists significant opportunity to exploit metrics that also allow for the study of the fluctuations of the atom delocalization in time. Here we consider the ring polymer delocalization from the perspective of computational topology, specifically persistent homology, which describes the 3-dimensional arrangement of point cloud data, (i.e. atomic positions). We employ the Betti sequence probability distribution to define the ensemble of shapes adopted by the ring polymer. The Wasserstein distances ofmore » Betti sequences adjacent in time are used to characterize fluctuations in shape, where the Fourier transform and associated principal components provides added information differentiating atoms with different NQEs based on their dynamic properties. We demonstrate this methodology on two representative systems, a glassy system consisting of two atom types with dramatically different de Broglie thermal wavelengths, and ab initio molecular dynamics simulation of an aqueous 4 M HCl solution where the H-atoms are differentiated based on their participation in proton transfer reactions.« less

Authors:

Hu, Yunfeng; Ounkham, Phonemany; Marsalek, Ondrej; Markland, Thomas E.; Krishmoorthy, Bala; Clark, Aurora E.

Publication Date:

Fri Mar 05 00:00:00 EST 2021

Research Org.:

Univ. of California, Merced, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)

OSTI Identifier:

1769441

Alternate Identifier(s):

OSTI ID: 1851928

Grant/Contract Number:  

SC0014437; DBI-1661348; DMS-1819229

Resource Type:

Published Article

Journal Name:

Frontiers in Chemistry

Additional Journal Information:

Journal Name: Frontiers in Chemistry Journal Volume: 9; Journal ID: ISSN 2296-2646

Publisher:

Frontiers Media SA

Country of Publication:

Switzerland

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Chemistry; path integral molecular dynamics; persistent homology; quantum delocalization; proton transfer; Wasserstein distances