Data-Driven Studies of the Magnetic Anisotropy of Two-Dimensional Magnetic Materials.

A key issue in layered materials is the dependence of their properties on their chemical composition and crystal structure in addition to the dimensionality. For instance, atomically thin magnetic structures exhibit novel spin properties that do not exist in the bulk. We use first-principles calculations, based on density functional theory, and machine learning to study the magnetocrystalline anisotropy of a set of single-layer two-dimensional structures that are derived from changing the chemical composition of the ferromagnetic semiconductor CrGeTe.

LAN: A Materials Notation for Two-Dimensional Layered Assemblies.

Two-dimensional (2D) layered materials offer intriguing possibilities for novel physics and applications. Before any attempt at exploring the materials space in a systematic fashion, or combining insights from theory, computation, and experiment, a formal description of information about an assembly of arbitrary composition is required. Here, we introduce a domain-generic notation that is used to describe the space of 2D layered materials from monolayers to twisted assemblies of arbitrary composition, existent or not yet fabricated.

Anatomy of the Photochemical Reaction: Excited-State Dynamics Reveals the C-H Acidity Mechanism of Methoxy Photo-oxidation on Titania.

Light-driven chemical reactions on semiconductor surfaces have potential for addressing energy and pollution needs through efficient chemical synthesis; however, little is known about the time evolution of excited states that determine reaction pathways. Here, we study the photo-oxidation of methoxy (CH3O) derived from methanol on the rutile TiO2(110) surface using ab initio simulations to create a molecular movie of the process. The movie sequence reveals a wealth of information on the reaction intermediates, time scales, and energetics.

Stress effects on the initial lithiation of crystalline silicon nanowires: reactive molecular dynamics simulations using ReaxFF.

Silicon (Si) has been recognized as a promising anode material for the next-generation high-capacity lithium (Li)-ion batteries because of its high theoretical energy density. Recent in situ transmission electron microscopy (TEM) revealed that the electrochemical lithiation of crystalline Si nanowires (c-SiNWs) proceeds by the migration of the interface between the lithiated Si (LixSi) shell and the pristine unlithiated core, accompanied by solid-state amorphization. The underlying atomic mechanisms of Li insertion into c-Si remain poorly understood.

Adsorption and diffusion of lithium on layered silicon for Li-ion storage.

The energy density of Li-ion batteries depends critically on the specific charge capacity of the constituent electrodes. Silicene, the silicon analogue to graphene, being of atomic thickness could serve as high-capacity host of Li in Li-ion secondary batteries. In this work, we employ first-principles calculations to investigate the interaction of Li with Si in model electrodes of free-standing single-layer and double-layer silicene.

Reactive flow in silicon electrodes assisted by the insertion of lithium.

In the search for high-energy density materials for Li-ion batteries, silicon has emerged as a promising candidate for anodes due to its ability to absorb a large number of Li atoms. Lithiation of Si leads to large deformation and concurrent changes in its mechanical properties, from a brittle material in its pure form to a material that can sustain large inelastic deformation in the lithiated form. These remarkable changes in behavior pose a challenge to theoretical treatment of the material properties.

Two-dimensional ordered porous patterns by molecular design.

We demonstrate by computer experiments that the spontaneous formation of two-dimensional regularly patterned molecular networks containing voids may be an entirely entropy-driven process. On the basis of a simple model of core-(soft) shell half-disk-shaped particles, we show that, even without the mediation of any attractive interparticle forces, such particles self-organize to stable and macroscopically ordered patterns with regularly distributed voids. The morphology of these supramolecular porous motifs depends critically on the size of the core relative to the coronal halo.