The adsorption of transition metal oleates on Pt nanoparticle surfaces creates a negative charge, promoting selective hydrogenation of CO bonds over CC bonds in nonpolar solvents, ensuring reactant solubility and improving catalytic efficiency.

A novel analysis of the dynamical behavior of nanoalloy systems, as represented by model Ni/Al 13-atom clusters, over a broad range of energies that cover the stage-wise transition of the systems from their solid-like to liquid-like state is presented. Conceptually, the analysis is rooted in partitioning the systems into judiciously chosen subsystems and characterizing the latter in terms of subsystem-specific dynamical descriptors that include dynamical degrees of freedom, root-mean-square bond-length fluctuation, and element-specific subsystem temperature. The analysis reveals a host of intriguing new peculiarities in the dynamical behavior of the Ni/Al 13-mers, among which are what we call the chameleon effect and the difference in the temperatures of the Ni and Al subsystems at high energies, a difference that strongly depends on the cluster composition and also changes with energy. These do not have an analog in pure Ni13 and Al13 and are explained in terms of the coupled effects of the difference between the masses of the Ni and Al atoms (the mass effect) and of the difference in the anharmonicity of the overall interaction potential as experienced by the Ni and Al subsystems of the clusters (the potential effect).

The Cover Feature displays the graphs of the vibrational temperature of a 13-atom Ni/Al cluster as a function of its composition and internal energy. For each composition, the energy range shown corresponds to the onset of global isomeric and homotopic structural changes and eventual transition to the liquidlike state. The graphs indicate an increase in the degree of stability of the cluster as its composition changes towards 50/50% either from the side of the pure Ni13 or pure Al13 (see the article for details). The pictures for the different compositions show the corresponding lowest energy equilibrium form of the cluster. Cover design by D. Aleinikava and J. Jellinek. More information can be found in the Research Article by Darya Aleinikava and Julius Jellinek.

Results of size-selected electron photo-detachment experiments and density functional theory calculations on anionic AlnPt-, n = 1-7, clusters are presented and analyzed. The measured and calculated spectra of electron binding energies are, overall, in excellent accord with each other. The analysis reveals the general importance of accounting for the multiplicity of structural forms of a given-size cluster that can contribute to its measured spectrum, especially when the clusters are fluxional and/or the conditions of the experiment allow for structural transitions. We show that for the systems studied here, the size-specific peculiarities of the measured spectra can be understood in terms of the combined contributions of corresponding different accessible stable equilibrium conformations, bona-fide transition-state configurations, and electronic-crossing structures that may play the role of effective barriers in electronically nonadiabatic dynamics.

Results of density functional theory calculations on Aln− and Aln−1Pt−, n = 2–8, clusters are presented and analyzed. The analysis includes different structural forms of the clusters characterized in terms of binding energy, spin and symmetry, and a comparative evaluation of various properties of the two systems viewed as connected through a single-Pt substitutional doping and examined in terms of their respective most stable structures. The Aln−1Pt− clusters are then used as a paradigmatic (model) case of single-atom nanocatalysts, with Pt as the catalytic center and Aln−1 as its support, to implement a uniform descriptor for gauging the tuning effects of all the parameters (“knobs”) of a nanocatalyst that include the identity of the active center and the material and size of its support.

The added technological potential of bimetallic clusters and nanoparticles, as compared to their pure (i.e., one-component) counterparts, stems from the ability to further fine-tune their properties and, consequently, functionalities through a simultaneous use of the “knobs” of size and composition. The practical realization of this potential can be greatly advanced by the knowledge of the correlations and relationships between the various characteristics of bimetallic nanosystems on the one hand and those of their pure counterparts as well as pure constituent components on the other hand. Here, we present results of a density functional theory based study of pure Ptn and Mon clusters aimed at revisiting and exploring further their structural, electronic, and energetic properties. These are then used as a basis for analysis and characterization of the results of calculations on two-component Ptn-mMom clusters. The analysis also includes establishing relationships between the properties of the Ptn-mMom clusters and those of their Ptn-m and Mom components. One of the particularly intriguing findings suggested by the calculated data is a linear dependence of the average binding energy per atom in sets of Ptn-mMom clusters that have the same fixed number m of Mo atoms and different number n-m of Pt atoms on the fractional content (n-m)/n of Pt atoms. We derive an analytical model that establishes the fundamental basis for this linearity and expresses its parameters—the m-dependent slope and intercept—in terms of characteristic properties of the constituent components, such as the average binding energy per atom of Mom and the average per-atom adsorption energy of the Pt atoms on Mom. The conditions of validity and degree of robustness of this model and of the linear relationship predicted by it are discussed.

The absorptive characters of O-2 on Fe31MnC(001) surface at three different sits (top, bridge and hollow) and effect of C on the magnetic properties of Fe31Mn were investigated by the generalized gradient approximation (GGA) based on density functional theory (DFT). The results indicate that O-2 tends to be vertically over the four-coordination vacancy hollow site. For Oxygen atom adsorption, it has a larger adsorption energy when oxygen atoms occupy the adjacent four-coordination vacancy hollow site. The dissociative adsorption of oxygen molecules occurs on the surface with Mn as the surface atom, and the bridge adsorption is the most favorable adsorption site. Meanwhile, carbon atom not only increases the magnetization hybridization of matrix, but also inhibits antiferromagnetic interaction of the adjacent Fe and Mn atoms.

The properties and characteristics of materials on the subnano/nano scale are very different from those of their bulk counterparts. The evolution of materials properties with size is the holy grail of nanoscience. An intriguing question then is: Can one predict what type of material (metal, semiconductor or insulator) an unidentified element will be, when in bulk quantities, solely from the properties it exhibits over a limited range of the subnano/nano size-regime? We demonstrate here that for nominally metallic elements (i.e., elements that are metals in bulk quantities) the answer to this question is "yes", and the very identity of the element also can be established. Most importantly, we show that the phenomenon of size-induced transition to metallicity, as gauged by polarizability, is characterized by features and trends that are universal for all metals. Combining numerical simulation data with an analytical model we introduce a universal constant and derive equations that express the universality explicitly.

Results of photoelectron spectroscopy measurements and density functional theory complemented with correction scheme calculations on electron binding energy (EBE) spectra of anionic AlnMo, n = 3–5 and 7, clusters are presented and analyzed. The analysis points to the important role of dynamical fluxionality and multiplicity of structural forms as contributing factors in the measured spectra. Using the example of Al4Mo– as a paradigmatic case, the separate roles of size, structure/symmetry, and composition in evolving the EBE spectra of precursor pure clusters (in this case, Al4– and Al5–) into those of bimetallic clusters are demonstrated utilizing a new methodology we developed recently (J. Phys. Chem. C 2017, 121, 16665).

High entropy alloy (HEA) thin coatings have been deposited on steel substrate of a mixed alloy power made of high purity elemental aluminium, cobalt, chromium, copper, iron and nickel by electron beam evaporation and effects of the Al content of the coating on its structure, surface morphology and electrical properties were investigated. The results of X-ray diffraction (XRD) show that coatings are typical dendrite and interdendrite structures with different aluminum contents. The coatings' surface chemical components are basically similar to originally designed alloys by electron probe micro-analyzer (EPMA). Atomic force microscopy (AFM) results indicate that the modified surface of all coatings are very smooth and uniform. HEA coatings exhibit wide passive regions>700 mV in aqueous solutions of H2SO4 and NaCl. A large corrosion potential (−129 mV) and a small corrosion current density (≈2.2×10−6 A/cm2) clearly reveals that the corrosion resistance of the Al0.5FeCoCrNiCu coating is superior to that of the coatings.

A theoretical/computational description and analysis of the spectra of electron binding energies of Al-12(-), Al-13(-), and Al12Ni- clusters, which differ in size and/or composition by a single atom yet possess strikingly different measured photoelectron spectra, is presented. It is shown that the measured spectra can not only be reproduced computationally with quantitative fidelity-this is achieved through a combination of state-of-the-art density functional theory with a highly accurate scheme for conversion of the Kohn-Sham eigenenergies into electron binding energies but also explained in terms of the effects of size, structure/symmetry; and composition. A new methodology is developed and applied that provides for disentanglement and differential assignment of the separate roles played by size, structure/symmetry, and composition in defining the observed differences in the measured spectra. The methodology is general and applicable to any finite system, homogeneous or heterogeneous. We project that in combination with advances in synthesis techniques this, methodology will become an indispensable computation-based aid in the design of controlled synthesis protocols for manufacture of nanosystems and nanodevices with precisely desired electronic and other characteristics.

A stable and structurally well-defined titanium alkoxide catalyst supported on a metal-organic-framework (MOF) of UiO-67 topology (ANL1-Ti(OPr)(2)) was synthesized and fully characterized by ayariety of analytical and spectroscopic techniques, including BET, TGA, PXRD, XAS, DRIFT, SEM, and DET computations. The Ti- functionalized MOF was demonstrated active for the catalytic hydroboration of a wide range of aldehydes and ketones with HBpin as the boron source. Compared to traditional homogeneous and supported hydroboration catalysts) ANL1-Ti(OPr)(2) is Completely recyclable and reusable, making it a promising hydroboration catalyst alternative for green and sustainable chemical synthesis. In addition, ANL1-Ti(OPr)(2) Catalyst exhibits remarkable hydroboration selectivity toward aldehydes vs ketone.in competitive study. DFT calculations suggest that the catalytic hydroboration proceeds via a (1) hydride transfer between the active Ti-hydride species and a carbonyl moiety (rate-determining step) and (2) alkoxide transfer (intramolecular sigma-bond metathesis) to generate the borate ester product.

Density of states is a fundamental physical characteristic that lies at the foundation of statistical mechanics and theoretical constructs that derive from them (e.g., kinetic rate theories, phase diagrams, and others). Even though most real physical systems are anharmonic, the vibrational density of states is customarily treated within the harmonic approximation, or with some partial, often limited, account for anharmonicity. The reason for this is that the problem of anharmonic densities of states stubbornly resisted a general and exact, yet convenient and straightforward in applications, solution. Here we formulate such a solution within both classical and quantum mechanics. It is based on actual dynamical behavior of systems as a function of energy and as observed, or monitored, on a chosen time scale, short or long. As a consequence, the resulting anharmonic densities of states are fully dynamically informed and, in general, time-dependent. As such, they lay the ground for formulation of new statistical mechanical frameworks that incorporate time and are ergodic, by construction, with respect to actual dynamical behavior of systems.

Dipole polarizabilities were computed using density functional theory for silicon clusters over a broad range of sizes up to N = 147 atoms. The calculated total effective polarizabilities, which include contributions from permanent dipole moments of the clusters, are in very good agreement with recently measured values. We show that the permanent dipole contributions are most important for clusters in the intermediate size range and that the measured polarizabilities can be used to distinguish between energetically nearly degenerate cluster isomers at these sizes. We decompose the computed total polarizabilities α into the so-called dipole and charge transfer contributions, αp and αq, using a site-specific analysis. When the per-atom values of these quantities are plotted against N-1/3, clear linear trends emerge that can be extrapolated to the large size limit (N-1/3→0), resulting in a value for αN of 30.5 bohrs3/atom that is significantly larger than the per-atom polarizability of semiconducting bulk Si, 25.04 bohrs3/atom. This indicates that Si clusters possess a higher degree of metallicity than bulk Si, a conclusion that is consistent with the strong electrostatic screening of the cluster interiors made evident by the analysis of the calculated atomic polarizabilities.

We investigate atom-diatom reactive collisions, as a preliminary step, in order to assess the possibility of forming Rb2 molecules in their lowest triplet electronic state by cold collisions of rubidium atoms on the surface of helium nanodroplets. A simple model related to the well-known Rosen treatment of linear triatomic molecules [N. Rosen, J. Chem. Phys. 1, 319 (1933)] in relative coordinates is used, allowing to estimate reactive probabilities for different values of the total angular momentum. The best available full dimensional potential energy surface [Guillon et al., J. Chem. Phys. 136, 174307 (2012)] is employed through the calculations. Noticeable values of the probabilities in the ultracold regime, which numerically fulfill the Wigner threshold law, support the feasibility of the process. The rubidium dimer is mainly produced at high vibrational states, and the reactivity is more efficient for a bosonic helium partner than when the fermion species is considered.

This chapter address the following question: does the size and constituent hierarchy atoms → clusters → condensed matter imply at least some degree of universality in the properties of matter on different length scales. A related question is: does the above hierarchy mean that the properties of clusters can be derived from the properties of atoms, and the properties of condensed matter can be derived from the properties of clusters. An objective (beyond intuitive) basis for the answer to the second question should be rooted in our ability to account correctly for all the relevant interactions and the changes in these interactions with the system size. There is also room for alternative approaches that aim at applications in a specific size range or over a given length scale and that target adequate interaction potentials and force fields without recourse to a rigorous derivation from a more detailed description.