Laboratory for Surface Modification (LSM)

Seminars Archives

March 2021 | April 2021

Thursday, April 01, 2021
Unravelling the Origins of Functionality through Correlative Multimodal Chemical Imaging
Olga S. Ovchinnikova
Multimodal Data Analytics Group/Computational Sciences and Engineering Division
Oak Ridge National Laboratory
12:00pm ZOOM

The key to advancing energy materials and biological systems is to understand and control the structure and chemistry at interfaces. While much of the dynamic chemistry can be studied on macro-scale systems, there is a lack of means to localize chemical measurements and correlate them to nanoscale structure of the material. Through a unique merger of advanced scanning probe and microscopy with mass spectrometry techniques rooted in innovative machine learning and control algorithms, we are now able to understand the interplay between chemical and physical functionality at the fundamental length scales using multimodal chemical imaging. This multimodal imaging transcends existing techniques by providing nanoscale structural imaging with simultaneous chemical analysis. Here, I will discuss how we have developed and used this capability to visualize dynamic material transformations at interfaces, to correlate these changes with chemical composition, and to distil key performance-centric material parameters. One exciting capability is that the AFM can be used to drive materials away from equilibrium at the nanoscale with highly localized electric fields. This allows field confinement effects on localized chemistry in materials to be locally probed, especially at interfaces. This in turn yields direct information on key energy related questions such as electron and ion motion distribution and transport at and between interfaces. Overall, I will focus on ways to unlock the mystery of active interface formation through intertwining data analytics, nanoscale elemental and molecular characterization, with imaging; to better grasp the physical properties of materials and the mechanistic physics-chemistry interplay behind their properties.


Thursday, April 08, 2021
Finding surface structure with evolutionary algorithms and reinforcement learning
Bjørk Hammer
Professor, VILLUM Investigator
Dept. of Physics and Astronomy
Aarhus University
12:00pm ZOOM

Atomistic simulations of the physico-chemical processes at inorganic surfaces often require knowledge of the energetically most optimal state of the surfaces. In this talk, examples are given of intricate surface reconstructions and surprising shapes assumed by metal nano-particles supported on oxide surfaces. The focus of the talk will be on how to identify such optimal structure given a costly total energy method as implemented in an electronic structure program, typically a density functional theory program (DFT). A number of approaches will be presented. 1) A pure evolutionary approach in which new structural candidates are created by random cross-over and mutation operations, 2) a machine learned-enhanced evolutionary approach in which an on-the-fly learned surrogate energy landscape directs the candidate production, and finally 3) a pure reinforcement learning approach in which image recognition via a convolutional neural network is used to build up rational knowledge about the energy landscape, that eventually leads to the construction of globally optimal structure.

[1] Evolutionary approach (EA): Phys. Rev. Lett. 108, 126101 (2012).

[2] ML assisted EA: Phys. Rev. Lett. 124, 086102 (2020) and https://gofee.au.dk

[3] Reinforcement learning: Phys. Rev. B, 102, 075427 (2020).
Thursday, April 15, 2021
Advances in Single-Particle Spectroscopy Using Fast Electrons
David Masiello
University of Washington
12:00pm ZOOM

In this talk I will highlight our recent research in low-loss STEM-EELS in collaboration with Jon Camden (Notre Dame), Philip Rack (Tennessee), and Juan Carlos Idrobo (ORNL). Emphasis will be placed on modeling the interaction of the fast electron probe with surface plasmon and photonic cavity modes in individual nanoparticles and their few-particle assemblies. Several topics ranging from plasmonic energy transfer, weak-to-strong coupling, Fano antiresonances, and magnetic plasmon hybridization will be discussed.
Thursday, April 22, 2021

Chris Leighton
University of Minnesota
12:00pm ZOOM
Thursday, April 29, 2021

Xiaodong Xu
11:30am ZOOM

You may also view a summary of past and upcoming seminars.