MSE Colloquium: Richard Hennig, Materials Informatics for the Discovery of Novel 2D Materials

Abstract

The rapid rise of novel single-layer materials presents the exciting opportunity for materials science to explore an entirely new class of materials. This comes at the time when mature computational methods provide the predictive capability to enable the computational discovery, characterization, and design of single-layer materials and provide the needed input and guidance to experimental studies. I will present our data-mining, chemical substitution, and evolutionary algorithm approaches to identify novel 2D materials with low formation energies and show how unexpected structures emerge when a material is reduced to sub-nanometers in thickness. To identify 2D materials that can be synthesized by exfoliation of bulk materials, we searched the Materials Project crystal structure database for materials possessing layered motifs in their crystal structures using a topology-scaling algorithm. The algorithm identifies and measures the sizes of bonded atomic clusters in a structure’s unit cell, and determines their scaling with cell size. The search yielded 680 monolayers with exfoliation energies below those of already-existent 2D materials. These materials guide future experimental synthesis efforts. Among the 2D materials, we find that for several 2D transition-metal chalcogenide compounds ferromagnetic order emerges at temperatures accessible to experiments. Calculations of the magnetic anisotropy show that many of the magnetic 2D materials exhibit an easy-plane for the magnetic moment and hence a Berezinsky-Kosterlitz-Thouless transition to a magnetically ordered low-temperature phase. A few 2D materials display an easy magnetization axis and thus an actual ferromagnetic ground state. Furthermore, we identify a family of three magnetic 2D materials with half-metallic band structures. Their purely spin-polarized currents and dispersive interlayer interactions should make these materials useful for 2D spin valves and other spintronic applications. These new 2D materials provide the opportunity to investigate the interplay of magnetic order and reduced dimensionality and may provide materials suitable for optoelectronic and spintronic applications. The structures and other calculated data for all 2D materials are available in the MaterialsWeb database at https://materialsweb.org.