Disorder and Entropy as Design Principles

Project Description

This grand challenge program aims to discover new materials required by emerging technologies by utilizing the unique and surprising effects of structural, chemical, magnetic, and electronic disorder. While all engineering materials contain defects in small concentrations that greatly affect the materials’ performance, new phenomena can appear when 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 the promise of improving the performance of lithium ion batteries and fuel cells, can help with waste energy recovery through thermoelectric energy conversion, or lead to better catalysts. They can also act as pinning centers in the macroscopic quantum state of  high temperature superconductors strongly enhancing the critical currents but also the supercondiucting transition temperatures. In addition higher concentration of specially selected defects or chemical substitutions in Heisenberg quantum antiferromagetic insulators have demonstrated reversable 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.

This research program will discover new materials for a better environment, in particular for energy storage and energy conversion technologies. A robust solid state battery technology will form the backbone of electromobility, and fuel cell technology is being developed as a competing technological platform with distinct advantages and disadvantages. Efficient conversion of waste heat to electricity can make an important contribution to tackling climate change, one of humankind’s most existential threats. The improved resistance to corrosion and wear as well as superior mechanical stability of amorphous metals and oxides will find applications in detectors, optical waveguides, power generation and transmission, and electrochromics. This research program implements the materials-by-design paradigm by closely linking materials theory and simulation both from classical and quantum approaches with novel synthesis methods and materials characterization, and will contribute to establishing SBQMI as a world leading centre for materials discovery.

We have identified six specific target areas where the presence of high concentrations of defects leading to high entropy is most likely to lead to new and improved material properties:

  1. Harnessing improved lithiation and high ion mobility in high entropy oxides (HEO)
  2. Tuning thermal conductivity and thermoelectric effect in high entropy alloys (HEA)
  3. Structural glasses with improved stability
  4. Optimizing magnetic properties of high entropy alloys
  5. High entropy alloys for hydrogen storage and diffusion membranes
  6. Realizing quantum holography in strongly interacting disordered quantum systems

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


    Jörg Rottler, Team Lead 
    SBQMI
    UBC Physics & Astronomy


    Curtis Berlinguette 
    SBQMI
    UBC Chemistry


    Marcel Franz
    SBQMI
    UBC Physics & Astronomy


    Alannah Hallas 
    SBQMI
    UBC Physics & Astronomy


    Alireza Nojeh
    SBQMI
    UBC Electrical & Computer Engineering


    George Sawatzky​
    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. Please review the position descriptions below if you are interested in becoming involved with this proposal. Contact the Principal Investigator if you would like to find out more about the role.

    Postdoctoral Opportunities

    Postdoctoral Fellow: Ab-initio thermodynamics and transport properties of high entropy oxides

    Responsibilities:
    This position will utilize ab initio simulations in combination with empirical potential modeling to assess the role of entropy in the stabilization of high entropy alloys and oxides for potential use in lithium batteries and thermoelectrics. In order to address the need for large supercells, novel DFT formulations will be explored. First-principle calculations of the binding energies and activation energies of lithium ions in candidate materials will also be performed in order to assess ion mobilities. For thermal transport calculations, ab initio force constants will be used in perturbative treatments based on the Boltzmann Transport equation. The candidate should have experience with electronic structure methods and atomistic modeling in solid state physics.

    To apply for this position contact: Jörg Rottler

    Postdoctoral Fellow: Solvation thermodynamics

    Responsibilities:
    This position will explore the role of entropy in the solvation of ions and the resulting polarization effects of the solvating medium. Advanced sampling techniques in atomistic simulations will be used to precisely calculate solvation free energies in the fluid state and hence resolve the configurational entropy changes in the solvation cloud of ions relevant for battery applications. In the solid state, vibrational, electronic, and spin contributions to the entropy must be considered. The candidate should have expertise with classical and/or ab initio molecular dynamics simulations of complex fluids and ideally has prior knowledge in the development of coarse-grained/effective solvent models.

    To apply for this position contact: Jörg Rottler

    Postdoctoral Fellow: Material synthesis and characterization

    Responsibilities:
    Working closely with theory counterparts, this position will synthesize candidate materials that were identified via ab-initio calculations for potential use in lithium batteries and thermoelectrics. This position will also be responsible for designing a synthetic pathway to prepare bulk samples of high entropy alloys and high entropy oxides and their structural characterization using both average (diffraction) and local (microscopy) probes. The candidate should have prior experience in materials synthesis and/or crystal growth in the bulk or thin films, crystallography, and other complementary property measurements.

    To apply for this position contact: Alannah Hallas

    Postdoctoral Fellow: Discovery of new high-entropy alloys (HEAs) for hydrogen storage and diffusion membranes

    Responsibilities:
    This position will seek to identify a free-standing HEA membrane that can serve as an alternative for Pdmembranes. In order to access the role of entropy in the hydrogen storage capacity, different HEA membrane compositions and thicknesses will be synthesized via arc-melting. The role will initially be guided by the Hallas group with the synthesis and structural characterization of HEAs. The role will also assess hydrogen absorption into the HEA membranes using coulometry measurements, and compare the results to state-of-the-art membranes. The successful candidate will also employ in situ x-ray power diffraction (XRD) to investigate structural changes resulting from absorption and desorption of hydrogen that induces lattice distortion. This candidate should have a PhD in Chemistry, Chemical Engineering, Materials Science or a related field with an emphasis in electrochemistry and/or electrochemical engineering.

    To apply for this position contact: Curtis Berliguette 

    Research Associate Opportunity

    Research Associate: Transport Phenomena for Energy Conversion and Storage, and Grand Challenge Integration

    Responsibilities:
    The research associate (RA) will investigate transport phenomena involved in the conversion and storage of energy in various materials. Relevant effects include the transfer of heat, charge, spin, and light, and particular emphasis is placed on exploiting low-dimensionality and quantum confinement in nanostructures. A special area of interest is the study of thermal conductivity and electron transport in new materials for thermal electricity generation. The RA will use a variety of characterization systems based on vacuum, optics, and electronic instrumentation, and should also have theoretical knowledge of transport phenomena and an ability to develop new experimental techniques. The RA will also be responsible to act as coordinator for the synthesis and characterization efforts within the Grand Challenge program.

    For more information and further details, please contact: Alireza Nojeh 
    To apply for this position, please visit www.facultycareers.ubc.ca/35781