Disorder and Entropy as Design Principles

This grand challenge program aims to discover new materials for emerging technologies by utilizing the unique and surprising effects of structural, chemical, magnetic, and electronic disorder.

While the performance of all engineering materials greatly depends on ever-present small concentrations of defects, new phenomena can develop if the defect concentration is strongly increased. For instance, metallic alloys and ceramics with a random placement of multiple atomic species on the crystal lattice hold multiple promises, including improving the performance of lithium ion batteries and fuel cells, helping with waste energy recovery through thermoelectric energy conversion, and leading to better catalysts. They can also act as pinning centers in the macroscopic quantum state of high-temperature superconductors, strongly enhancing critical currents and also superconducting transition temperatures. In addition, a higher concentration of specially selected defects or chemical substitutions in Heisenberg quantum antiferromagetic insulators have demonstrated reversible omnipolar switchable resistive memories.

Truly amorphous materials, in which the atomic positions themselves are disordered, exhibit superior wear and corrosion resistance that benefits applications in thin film coatings, detectors, and optical waveguides and can even result in a macroscopic superconducting quantum state, even if the crystalline material is not. While a large amount of empirical knowledge and models exist about the many useful properties of amorphous materials and alloys, our understanding of how these properties originate from atomic scale configurations and interactions which are so important in quantum materials is still in its infancy.

Through a "materials-by-design paradigm" linking materials theory, simulation and novel synthesis and characterization methods, this research program seeks to understand, at an atomic level, how novel material properties can emerge as the direct consequence of disorder. Our focus is directed on three classes of situations systems:

  1. High entropy materials - alloys and oxides - that contain randomly distributed mixtures of five or more chemical elements on a regular lattice;
     
  2. Thermal transport of disordered systems at high-temperature, where lattice oscillations are not well described by the quasi-particle picture;
     
  3. Structurally amorphous materials, where atomic constituents, regardless of their chemical nature, are not arranged on a regular crystal lattice.

As part of the first thrust, team members are studying the structure of lithium nickel oxide (LiNiO2), a precursor to a widely used lithium ion battery cathode material. In a recently published article, team members showed that LiNiO2 should not be thought of as a crystalline ordered material but a high-entropy glassy material. This novel perspective may pave the way for designing new cathode materials with improved performance.

In the second thrust, simulations and characterization are being combined to explain the origins of the 'heat trap' phenomenon displayed by Carbon nanotube forests discovered by our research teams. In the third thrust, Grand Challenge researchers are collaborating on the development of an improved mirror coating based on structurally amorphous materials for LIGO (the Laser Interferometer Gravitational-Wave Observatory) along with Jess McIver from UBC’s Department of Physics & Astronomy. LIGO made headlines in 2016 for the experimental observation of gravitational waves and improved detector coatings that have the potential to dramatically increase the sensitivity to astronomical events of next-generation gravitational wave detectors.
 

Disorder as a Design Principle is a Grand Challenge project investigating the mechanisms and conditions under which the different sources of entropy lead to novel material behaviour

Figure 1: Strong heat localization in carbon nanotubes
(Click to view full-size image.)

A figure showing a macroscopic-size carbon nanotube forest previously published in Physical Review B from the article, "Heat localization through reduced dimensionality" (Chang, Fan, Chowdhury, Sawatzky & Nojeh, 2018).
Description: A macroscopic-size carbon nanotube forest consisting of billions of millimeters-tall vertically aligned nanotubes. A low-power focused laser beam has illuminated a spot on the sidewall of the nanotube forest. Despite the conductive nature of nanotubes, the generated heat remains localized, forming a 'Heat Trap' and enabling efficient heating to very high temperatures at which strong black body radiation and thermionic emission take place. (The laser is infrared and not seen in the photo; the glow is due to localized incandescence.) This thermal confinement appears to have its origins in the low-dimensionality of the nanotube forest, and disorder and various forms of defects may also be playing an important role.

    Figure 2: LiNiO2 as a high-entropy charge- and bond-disproportionated glass
    (Click to view full-size image.)

    A figure showing the high-entropy of the LiNiO2 system previously published in Physical Review B from the article, "LiNiO2 as a high-entropy charge- and bond-disproportionated glass" (Foyevtsova, Elfimov, Rottler & Sawatzky, 2019). Image by Kateryna Foyevtsova. 
    Description: The left panel shows the layered structure of LiNiO2, a system that shows very high capacity as a cathode material in Li-ion batteries. The middle panel show the NiO2 plane with a triangular arrangement of the edge-sharing NiO6 octahedra. The right panel shows an inhomogeneous quasi-random distribution of oxygen charge in our propose entropy-stabilized charge-glass-like state in LiNiO2, which originates from a variance from site to site occupation of oxygen molecular orbitals painted in different colors. Depending on which oxygen molecular orbitals are occupied on a given Ni site, there are sites with 6 short Ni-O distances (indicated by black sticks), 4 short and 2 long Ni-O distances, or all 6 long Ni-O distances. We believe that the high-entropy of the LiNiO2 system is the prime reason for its high capacity and stability upon Li extraction.


    Principal Investigators


    Jöerg Rottler, Team Lead 
    SBQMI
    UBC Physics & Astronomy


    Curtis Berlinguette 
    SBQMI
    UBC Chemistry


    Alannah Hallas 
    SBQMI
    UBC Physics & Astronomy

    Jess McIver
    Jess McIver
    UBC Physics & Astronomy
     


    Alireza Nojeh
    SBQMI
    UBC Electrical & Computer Engineering


    George Sawatzky​
    SBQMI
    UBC Physics & Astronomy


    Jeff Young
    SBQMI
    UBC Physics & Astronomy


    Ke Zou
    SBQMI
    UBC Physics & Astronomy


    Current Opportunities

    SBQMI is looking to fill a number of important positions for this high-profile project. The team will work closely together to deliver the objectives set out above. Postdoctoral fellows will be expected to exhibit leadership and be able to work independently to deliver results. Contact Jöerg Rottler if you would like to find out more about the role.