Repetitive Rolling of Triptycene-Based Molecules on Cu Surfaces.

The metal surface-supported rotation of artificial molecular structures is technologically important for developing molecular-level devices. The key factors leading to the practical applications of these molecular machines on metal surfaces are the atomic-scale control of the rotation and the counterbalance of the temperature-driven instability of the molecules. In this work, we present a means by which triptycene-based molecular wheels can roll repetitively on a metal surface.

Adsorption of oleic acid on magnetite facets.

The microscopic understanding of the atomic structure and interaction at carboxylic acid/oxide interfaces is an important step towards tailoring the mechanical properties of nanocomposite materials assembled from metal oxide nanoparticles functionalized by organic molecules. We have studied the adsorption of oleic acid (CHCOOH) on the most prominent magnetite (001) and (111) crystal facets at room temperature using low energy electron diffraction, surface X-ray diffraction and infrared vibrational spectroscopy complemented with molecular dynamics simulations used to infer specific hydrogen bonding motifs between oleic acid and oleate. Our experimental and theoretical results give evidence that oleic acid adsorbs dissociatively on both facets at lower coverages.

Growth and shape stability of Cu-Ni core-shell nanoparticles: an atomistic perspective.

The growth and shape stability of bi-metallic cubic Cu-Ni nanoparticles are studied using atomic-level simulations. Cubic nano-crystals coated with an ultra-thin Cu layer can be readily obtained when Ni cubic nanoparticles are used as the seeds. At elevated temperatures, the Cu seed with extending Ni branches preserves its shape compared to the Ni seed with extending Cu branches.

Two-Dimensional Fluorinated Boron Sheets: Mechanical, Electronic, and Thermal Properties.

The synthesis of atomically thin boron sheets on a silver substrate opened a new area in the field of two-dimensional systems. Similar to hydrogenated and halogenated graphene, the uniform coating of borophene with fluorine atoms can lead to new derivatives of borophene with novel properties. In this respect, we explore the possible structures of fluorinated borophene for varying levels of coverage (B F) by using first-principles methods.

The interaction of halogen atoms and molecules with borophene.

The realization of buckled monolayer sheets of boron (i.e., borophene) and its other polymorphs has attracted significant interest in the field of two-dimensional systems.

Shape-controlled growth of metal nanoparticles: an atomistic view.

Recent developments in shape-controlled synthesis of metallic nano-particles present a promising path for precisely tuning chemical activity, selectivity, and stability of nano-materials. While previous studies have highlighted the macroscopic description of synthesis processes, there is less understanding as to whether individual atomic-scale processes possess any significant role in controlling the growth of nano-products. The presented molecular static and dynamic simulations are the first simulations to understand the underlying atomistic mechanisms of the experimentally determined growth modes of metal nano-clusters.

Strain-induced structural transformation of a silver nanowire.

We have investigated the structural characteristics of the experimentally observed phase transition of a silver nanowire into a tube under tensile strain. In the simulations, atoms are allowed to interact via a model potential extracted from the modified embedded atom method. Our calculations demonstrate that the formation of the hollow structure is governed by the nature of the applied strain, the length of the wire, and the initial cross-sectional shape.

Energetics and atomic relaxations of Cu nanowires: the effect of local strain and cross-sectional area.

We have calculated the activation energies for several single atom and vacancy diffusion processes on Cu nanowires with the axial orientation of [Formula: see text], using the nudged elastic band technique based on the interaction potential obtained from the embedded atom method. It is shown that the dimer-initiated local strain and its relief at the transition state have a significant effect on the characteristics of self-surface diffusion mechanisms on nanowires. Contrary to the case for cylindrical multishell-type Cu nanowires, the vacancy formation energy for rectangular nanowires is maximum in the core region and is nearly zero at the corner of the nanowire.