Title：Chemical Templates that Assemble the Metal Superhydrides

Speaker：Maosheng Miao，California State University Northridge

Time：Aug 17, 2022 10:00

Zoom ID：950 680 6742

Abstract：The recent incessant discoveries of high-pressure metal superhydrides fulfill Ashcroft’s idea of achieving metallic hydrogen by chemical precompression and bring us ever close to room temperature superconductivity. However, the true chemical force that drives the dissociation of H2 and the formation of an H covalent network in these compounds with exceedingly high H composition is still unknown, although several assumptions such as electron doping and close-packing are readily available. Besides the chemical force, a valid mechanism is expected to explain why only metals at the s-d border (Sc, Y, La, Ce, Hf, etc.) are inclined to form superhydrides, and also to provide robust predictions to more complex systems such as ternary and quaternary superhydrides that are extremely challenging for DFT calculations but inevitable for finding materials with high Tc at lower pressure. Using high-throughput calculations, we show that, after removing all the H atoms, the remaining metal lattices exhibit an unusual electron distribution at the interstitial regions due to their occupation of the quasi-atom orbitals. Strikingly, this electron feature of the metal lattice matches excellently to the H lattice like a template. Especially, H lattices consist of aromatic building units that are greatly stabilized by the metal lattices. This chemical template theory resolves important issues of superhydride formation and shows good potential in searching for new mixed metal superhydrides (ternary compounds) that could be stabilized by large metal-metal interactions and still maintain a strong template effect.

Brief Bio：Dr. Maosheng Miao obtained his Ph.D. in physical chemistry at Jilin University in China. He worked at many places as a postdoc and research scientist, including the University of Antwerp, Case Western Reserve University, Washington State University, and the University of California Santa Barbara. Since 2015, he works in the Department of Chemistry and Biochemistry at California State University Northridge. He has more than 20 years of working experience and background in first principles calculations of the atomic and electronic structures of materials and solid-state chemistry. He has worked in many areas of computational materials science, ranging from semiconductor defects, surfaces and interfaces, functional oxides, solid-state lighting materials, two-dimensional materials, and high-pressure physics and chemistry.