Size-Dependent Ab Initio Atomistic Thermodynamics from Cluster to Bulk: Application to Hydration of Titania Nanoparticles.

Ab initio atomistic thermodynamics (AIAT) has become an indispensable tool to estimate Gibbs free energy changes for solid surfaces interacting with gaseous species relative to pressure () and temperature (). For such systems, AIAT assumes that solid vibrational contributions to Gibbs free energy differences cancel out. However, the validity of this assumption is unclear for nanoscale systems.

Gas-Phase Production of Hydroxylated Silicon Oxide Cluster Cations: Structure, Infrared Spectroscopy, and Astronomical Relevance.

The interaction of free cationic silicon oxide clusters, Si O ( = 2-5, ≥ ), with dilute water vapor, was investigated in a flow tube reactor. Product mass distributions indicate cluster size-dependent dissociative water adsorption. To probe the structure and vibrational spectra of the resulting Si O H ( = 2-4) clusters, we employed infrared multiple photon dissociation spectroscopy and density functional theory calculations.

Tuning electronic levels in photoactive hydroxylated titania nanosystems: combining the ligand dipole effect and quantum confinement.

Reducing the size of titania (TiO) to the nanoscale promotes the photoactive anatase phase for use in a range of applications from industrial catalysis to environment remediation. The nanoscale dimensions of these systems affect the magnitude of the electronic energy gap by quantum confinement. Upon interaction with aqueous environments or water vapour, the surfaces of these systems will also be hydroxylated to some degree.

Minimum conditions for accurate modeling of urea production via co-electrolysis.

Co-electrolysis of carbon oxides and nitrogen oxides promise to simultaneously help restore the balance of the C and N cycles while producing valuable chemicals such as urea. However, co-electrolysis processes are still largely inefficient and numerous knowledge voids persist. Here, we provide a solid thermodynamic basis for modelling urea production via co-electrolysis.

Predicting observable infrared signatures of nanosilicates in the diffuse interstellar medium.

The destruction time scale of dust in the diffuse interstellar medium is estimated to be an order of magnitude shorter than its residence time. Nevertheless, dust is observed in the interstellar medium, leading to the conclusion that reformation and grain growth must take place. Direct observations of nanometre-sized silicate grains, the main constituent of interstellar dust, would provide a smoking gun for the occurrence of grain condensation in the diffuse interstellar medium.

A machine learning potential for simulating infrared spectra of nanosilicate clusters.

The use of machine learning (ML) in chemical physics has enabled the construction of interatomic potentials having the accuracy of ab initio methods and a computational cost comparable to that of classical force fields. Training an ML model requires an efficient method for the generation of training data. Here, we apply an accurate and efficient protocol to collect training data for constructing a neural network-based ML interatomic potential for nanosilicate clusters.

Buckletronics: how compression-induced buckling affects the mechanical and electronic properties of sp-based two-dimensional materials.

We explore the mechanical and electronic response of sp-based two-dimensional materials under in-plane compression employing first principles density functional theory-based calculations. Taking two carbon-based graphynes (α-graphyne and γ-graphyne) as example systems, we show that the structures of both two-dimensional materials are susceptible to out-of-plane buckling, which emerges for modest in-plane biaxial compression (1.5-2%).

Emergent Spin Frustration in Neutral Mixed-Valence 2D Conjugated Polymers: A Potential Quantum Materials Platform.

Two-dimensional conjugated polymers (2DCPs)─organic 2D materials composed of arrays of carbon sp centers connected by π-conjugated linkers─are attracting increasing attention due to their potential applications in device technologies. This interest stems from the ability of 2DCPs to host a range of correlated electronic and magnetic states (e.g.

Crystal properties without crystallinity? Influence of surface hydroxylation on the structure and properties of small TiO nanoparticles.

Titania (TiO) nanoparticles (NPs) are widely employed in applications that take advantage of their photochemical properties ( pollutant degradation, photocatalysis). Here, we study the interrelation between crystallinity, surface hydroxylation and electronic structure in titania NPs with 1.4-2.

Stable Organic Radical for Enhancing Metal-Monolayer-Semiconductor Junction Performance.

The preparation of monolayers based on an organic radical and its diamagnetic counterpart has been pursued on hydrogen-terminated silicon surfaces. The functional monolayers have been investigated as solid-state metal/monolayer/semiconductor (MmS) junctions showing a characteristic diode behavior which is tuned by the electronic characteristics of the organic molecule. The eutectic gallium-indium liquid metal is used as a top electrode to perform the transport measurements and the results clearly indicate that the SOMO-SUMO molecular orbitals impact the device performance.

How graphenic are graphynes? Evidence for low-lying correlated gapped states in graphynes.

Graphynes can be structurally envisioned as 2D extensions to graphene, whereby linearly bonded carbon linkages increase the distance between trigonal carbon nodes. Many graphynes have been predicted to exhibit a Dirac-like semimetallic (SEM) graphenic electronic structure, which could potentially make them competitive with graphene for applications. Currently, most graphynes remain as attractive synthetic targets, and their properties are still unconfirmed.

An unconstrained approach to systematic structural and energetic screening of materials interfaces.

From grain boundaries and heterojunctions to manipulating 2D materials, solid-solid interfaces play a key role in many technological applications. Understanding and predicting properties of these complex systems present an ongoing and increasingly important challenge. Over the last few decades computer simulation of interfaces has become vastly more powerful and sophisticated.

Can calculated harmonic vibrational spectra rationalize the structure of TiC-based nanoparticles?

Nanoscale titanium carbide (TiC) is widely used in composites and energy applications. In order to design and optimize these systems and to gain a fundamental understanding of these nanomaterials, it is important to understand the atomistic structure of nano-TiC. Cluster beam experiments have provided detailed infrared vibrational spectra of numerous TiC nanoparticles with well defined masses.

Controlling pairing of π-conjugated electrons in 2D covalent organic radical frameworks via in-plane strain.

Controlling the electronic states of molecules is a fundamental challenge for future sub-nanoscale device technologies. π-conjugated bi-radicals are very attractive systems in this respect as they possess two energetically close, but optically and magnetically distinct, electronic states: the open-shell antiferromagnetic/paramagnetic and the closed-shell quinoidal diamagnetic states. While it has been shown that it is possible to statically induce one electronic ground state or the other by chemical design, the external dynamical control of these states in a rapid and reproducible manner still awaits experimental realization.

Twistable dipolar aryl rings as electric field actuated conformational molecular switches.

The ability to control the chemical conformation of a system via external stimuli is a promising route for developing molecular switches. For eventual deployment as viable sub-nanoscale components that are compatible with current electronic device technology, conformational switching should be controllable by a local electric field (i.e.

Neutral Organic Radical Formation by Chemisorption on Metal Surfaces.

Organic radical monolayers (r-MLs) bonded to metal surfaces are potential materials for the development of molecular (spin)electronics. Typically, stable radicals bearing surface anchoring groups are used to generate r-MLs. Following a recent theoretical proposal based on a model system, we report the first experimental realization of a metal surface-induced r-ML, where a rationally chosen closed-shell precursor 3,5-dichloro-4-[bis(2,4,6-trichlorophenyl)methylen]cyclohexa-2,5-dien-1-one () transforms into a stable neutral open-shell species () via chemisorption on the Ag(111) surface.

Structure and Properties of Nanosilicates with Olivine (MgSiO) and Pyroxene (MgSiO) Compositions.

Magnesium-rich silicates are ubiquitous both terrestrially and astronomically, where they are often present as small particles. Nanosized Mg-rich silicate particles are likely to be particularly important for understanding the formation, processing, and properties of cosmic dust grains. Although astronomical observations and laboratory studies have revealed much about such silicate dust, our knowledge of this hugely important class of nanosolids largely rests on top-down comparisons with the properties of bulk silicates.

Assessing the usefulness of transition metal carbides for hydrogenation reactions.

Transition Metal Carbides (TMCs) are proposed as replacements for and expensive late Transition Metals (TMs) as heterogeneous catalysts, often implying hydrogenation reactions or steps. Present density functional theory based calculations support using group IV TMCs and δ-MoC as viable TM alternatives, given the moderate exoergicity and affordable reaction step energy barriers.

Understanding H Formation on Hydroxylated Pyroxene Nanoclusters: Ab Initio Study of the Reaction Energetics and Kinetics.

The rate constants of H formation on five models of silicate nanoclusters with varying degrees of hydroxylation, (MgSiO)(HO), were computed over a wide temperature range [180-2000 K]. We tested nine combinations of density functional methods and basis sets for their suitability for calculating reaction energies and barrier heights, and we computed the minimum energy H + H → H reaction paths on each nanocluster. Subsequently, we computed the rate constants employing three semiclassical approaches that take into account tunneling and nonclassical reflection effects by means of the zero curvature tunneling (ZCT), the small curvature tunneling (SCT), and the one-dimensional semiclassical transition state theory (SCTST) methods, which all provided comparable results.

Electronic, Structural and Functional Versatility in Tetrathiafulvalene-Lanthanide Metal-Organic Frameworks.

Tetrathiafulvalene-lanthanide (TTF-Ln) metal-organic frameworks (MOFs) are an interesting class of multifunctional materials in which porosity can be combined with electronic properties such as electrical conductivity, redox activity, luminescence and magnetism. Herein a new family of isostructural TTF-Ln MOFs is reported, denoted as MUV-5(Ln) (Ln=Gd, Tb, Dy, Ho, Er), exhibiting semiconducting properties as a consequence of the short intermolecular S⋅⋅⋅S contacts established along the chain direction between partially oxidised TTF moieties. In addition, this family shows photoluminescence properties and single-molecule magnetic behaviour, finding near-infrared (NIR) photoluminescence in the Yb/Er derivative and slow relaxation of the magnetisation in the Dy and Er derivatives.