Two-Dimensional Materials from Data Filtering and Ab Initio Calculations

Progress in materials science depends on the ability to discover new materials and to obtain and understand their properties. This has recently become particularly apparent for compounds with reduced dimensionality, which often display unexpected physical and chemical properties, making them very attractive for applications in electronics, graphene being so far the most noteworthy example. Here, we report some previously unknown two-dimensional materials and their electronic structure by data mining among crystal structures listed in the International Crystallographic Structural Database, combined with density-functional-theory calculations. As a result, we propose to explore the synthesis of a large group of two-dimensional materials, with properties suggestive of applications in nanoscale devices, and anticipate further studies of electronic and magnetic phenomena in low-dimensional systems.

Popular Summary

Materials with reduced dimensionality are promising for applications such as electronic devices, solid-state lubricants, and sensors. Graphene—a monolayer of carbon atoms packed into a planar honeycomb lattice—is currently attracting the most attention because it possesses an unusual electronic structure, is very stable mechanically, and has a high thermal conductivity. Graphene, however, lacks a finite band gap, which is a necessary condition for using it in many electronic devices. Recent work suggests that the two-dimensional systems boron nitride and the transition-metal dichalcogenides are promising graphene alternatives, as they are semiconductors with finite band gaps. But, the number of systems explored so far has been limited because the synthesis and characterization of new materials are difficult and time consuming.

In this paper, we report a two-step computational approach to discovering new two-dimensional materials and studying their properties that is both cost effective and efficient. First, we define a set of geometrical characteristics, such as packing density and lattice constant asymmetry, that are associated with certain van der Waals bonded, layered structures (like graphite, the parent compound of graphene). We then screen the Inorganic Crystal Structure Database for compounds that match these criteria. This procedure has identified 92 compounds that could be easily exfoliated into two-dimensional sheets. Of these, we propose 40 for the first time as parent compounds for two-dimensional materials. Second, we use density-functional theory to calculate the electronic structure (density of states and band dispersion) of the two-dimensional building blocks of these compounds. These calculations predict whether the two-dimensional material is metallic or insulating, as well as if it undergoes magnetic ordering at low temperatures.

Our work suggests that the number of two-dimensional materials, and the variety of electronic structures these materials can form, is quite large. We expect this work will pave the way for further experimental and theoretical study in the field of functionalized materials science.

Figure 1

Computed band structure of ${\mathrm{ZrSe}}_2$ (left) and ${\mathrm{HfSe}}_2$ (right) along the high-symmetry directions $\Gamma \mathrm{\text{−}}M\mathrm{\text{−}}K\mathrm{\text{−}}\Gamma$. The Fermi level is at zero energy.

Figure 2

Density of states (upper panel) and band structure along the high-symmetry directions $\Gamma \mathrm{\text{−}}M\mathrm{\text{−}}K\mathrm{\text{−}}\Gamma$ (lower panel) of antiferromagnetic ${\mathrm{FeBr}}_3$. Note that the density of states is also shown as an atomic projected property. Also, the Fermi level is at zero. In the inset of the upper panel, the two-dimensional crystal structure is also shown.

Figure 3

Density of states (upper panel) and band structure along the high-symmetry directions $\Gamma \mathrm{\text{−}}M\mathrm{\text{−}}K\mathrm{\text{−}}\Gamma$ (lower panel) of ferromagnetic ${\mathrm{CrSiTe}}_3$. Note that the density of states is also shown as an atomic projected property. The Fermi level is at zero energy. In the inset of the upper panel, the two-dimensional crystal structure is also shown.