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