The ongoing technological advances necessitate the discovery of new materials with exceptional functional properties to ensure superior efficiency, stability, and cost effectiveness. [1-4] The available options are inadequate as long as the search is limited to the stable ground states of materials. Alternatively, the oft-overlooked arena of ‘metastable’phases promises us with limitless new possibilities. Indeed, the recent studies [4-7] suggest that the design and discovery of long-lived, thermodynamically metastable materials could potentially be the way forward for sustainable technologies. In my talk, I would present the experimental discovery of a few such metastable phases, namely 1) TiN2, which is a promising superhard material that contains unique nitrogen subunits with highly energetic N―N single bonds  2) Ti3N4, which is the first semiconducting titanium nitride known to date. 3) ZnxMn1-xO solid solution in metastable rocksalt phase  which is a promising photocatalyst for solar water splitting reaction and solar light harvesting applications. Although, these compounds possess positive enthalpies at room conditions, they were recovered in metastable form from high-pressure/temperature conditions. The strategy that was employed here by marrying first principles theoretical calculations to high-pressure synthetic techniques is a way forward towards sustainable development of novel metastable phases for real-life applications.
- W. Sun et al, Science Advances, 2, 1 (2016).
- D. Y. Kim et al, Nature Materials, 14, 169 (2015).
- B. Keimer, J. E. Moore, Nature Physics, 13, 1045 (2017).
- V. V. Brazhkin, “High-Pressure Synthesized Materials: Treasures and Hints” High Pressure Research, 27, 333 (2007).
- W. Sun et al, Thermodynamic Routes to Novel Metastable Nitrogen-Rich Nitrides, Chemistry of Materials, 29, 6936 (2017).
- V. S. Bhadram,D. Y. Kim and T. A. Strobel. “High-Pressure Synthesis and Characterization of Titanium Pernitride.” Chemistry of Materials, 28, 1616 (2016).
- V. S. Bhadram, H. Liu, E. Xu, T. Li, T. A. Strobel, “Semiconducting Cubic Titanium Nitride in the Th3P4 structure.” Physical Review Materials, 2, 011602 (R) (2018)
- V. S. Bhadram, Q. Cheng, C. K. Chan, Y. Liu, K. Landskron, and T. A. Strobel, “ZnxMn1-xO Solid Solutions in the Rocksalt Structure: Optical, Charge-Transport and Photoelectrochemical Properties. ACS Applied Energy Materials, 1, 260 (2018).