Search

This review analyzes the literature data and the results of studies of the Pt/CeO2‐based catalysts that are capable of providing the low‐temperature CO oxidation (LTO CO). The review summarizes the catalytic characteristics and the main properties of Pt/CeO2‐based catalysts necessary for the low‐temperature oxidation at T<50 °C. Analysis of the literature data on the use of physical methods of investigation and their correlation with the activity of Pt/CeO2 catalysts allowed us to conclude that the main active forms of platinum are small metallic clusters, single atoms Pt2+‐SA and oxide clusters PtOx interacting with ceria nanoparticles. It has been established that the most active forms are PtOx clusters, which provide a high reaction rate in the temperature range from −50 to +50 °C. Forms of ionic Pt2+ with different coordination with oxygen ensure the activity of catalysts starting at temperatures above 100 °C. Finally, small metallic clusters occupy an intermediate position, providing activity above 0 °C, but their instability and gradual transition to the oxidized state Pt2+/PtOx are noted. At the conclusion of the review, the results of mathematical modeling demonstrate the correct kinetics description of the low‐temperature CO oxidation based on the Mars‐van Krevelen and associative mechanisms. [ABSTRACT FROM AUTHOR]

Metallic clusters, ranging from 1 to 2 nm in size, have emerged as promising candidates for creating nanoelectronic devices at the single-cluster level. With the intermediate quantum properties between metals and semiconductors, these metallic clusters offer an alternative pathway to silicon-based electronics and organic molecules for miniaturized electronics with dimensions below 5 nm. Significant progress has been made in studies of single-cluster electronic devices. However, a clear guide for selecting, synthesizing, and fabricating functional single-cluster electronic devices is still required. This review article provides a comprehensive overview of single-cluster electronic devices, including the mechanisms of electron transport, the fabrication of devices, and the regulations of electron transport properties. Furthermore, we discuss the challenges and future directions for single-cluster electronic devices and their potential applications. [ABSTRACT FROM AUTHOR]

Hypothesis-driven experiments have been conducted to explore the spatial variability and potential ecological risk indices (RIs) of potentially toxic elements (PTEs) in untreated in situ effluent continuously discharged downstream by the Kumasi Abattoir Ghana (KAG). The study focused on seven PTEs  nickel (Ni), lead (Pb), cadmium (Cd), manganese (Mn), zinc (Zn), copper (Cu), and iron (Fe), based on these hypotheses: (i) Variations in PTE levels may be significant in the effluent; (ii) Comparative RI assessments based on the three background values  natural background values (NBVs) for freshwater, maximum admissible concentrations (MACs), and reference values (RVs) provide objective evaluations; and (iii) PTEs’ cluster distances are linked to RIs. Effluent samples were randomly collected in quintuplicates from the drainage receptacle and analyzed using standard methods. The spatial variability of PTEs was investigated using divisive hierarchical cluster analysis (DHCA). The RIs and their uncertainties were computed using Hakanson's equations and standard deviation (SD). PTE dispersion was analyzed using the coefficient of variation (CV). Analysis of variance (ANOVA) was employed to test for the significance of hypotheses 1 and 2, complemented by Scheffé's post-hoc test where significance was detected. Hypothesis 3 was investigated by analyzing PTE cluster distances and RIs based on Pearson's correlation metric. The DHCA produced two clusters Cd–Cu–Mn–Ni and Zn-(Fe)-Pb. The CVs (< 50 %) indicated medium variability, relatively uniform spatial distributions, and minimal fluctuations. High to very high RIs ± SDs obtained were 300 ± 57.5 (MACs), 2900 ± 500 (RVs), and 7666 ± 2980 (NBVs). The ANOVA yielded significant results for both hypotheses, while moderate to high correlations were obtained for the third hypothesis. While RIs provided compelling evidence of inimical effluent, the study highlights the influence of background values on RIs. It further suggests that the PTE cluster distances may be used as surrogates for the RIs.

A first-principle study of (Pt 3 Cu) n n = 10–11 nanoclusters was performed using the linear combination of Gaussian-type orbitals within the auxiliary density functional theory (ADFT) framework. Neutral, anionic and cationic clusters species were studied. To carry on a detailed exploration of the potential energy surface of these systems, Born-Oppenheimer molecular dynamics (BOMD) simulations have been performed. Several dozens of structures were taken along the generated BOMD trajectories as initial geometries for geometry optimizations. Successive geometry optimizations of these systems, in different electron spin multiplicities and without any type of restriction, were computed. The obtained optimized structures have been characterized by frequency analysis calculations. Computed minima structures, harmonic frequencies, average bond lengths, magnetic moments, spin density plots, dissociation energy, ionization potential and electron affinity are reported. The formation of octahedra moieties has been observed in the most stable structures. The findings of the growing pattern of these clusters can serve as guide to search a synthetic route that can yield nanoparticles with desired geometries and high stability. [ABSTRACT FROM AUTHOR]

The crystal structure of magnussonite, ideally Mn2+18[As3+6(Mn1+x)O18]2[(H2O, Clx, ☐) (H2O, ☐)]2, from Långban, Sweden, was refined to an R1-index of 1.19% and the structure proposed by Moore and Araki (1979) is confirmed. Magnussonite has a densely packed structure of (Mnφn) polyhedra, φ = (O2−, H2O, Cl−), and (As3+O3) triangular pyramids that is best envisaged as layers of polyhedra in the same way as many of the other manganese-arsenite-arsenate structures from Långban. There are two distinct layers in magnussonite; the two layers may be combined into a slab that stacks along the a-direction with rotations between adjacent slabs. A surprising feature of the dense-packed magnussonite atomic arrangement is an array of structural channels along [111] that contain much of the disorder that occurs in the magnussonite structure. The channels contain the partly occupied MX site on the central axis of the channel, and the CLW2 site (with extremely low occupancy), also on the central axis of the channel. The CLW2 site, previously unrecognized in the magnussonite structure, contains H2O, whereas the minor Cl in the structure resides in the CLW1 channel site, balancing the charge of the MX-site occupant. The MX site on the central axis of the channels displays a coordination known only in Långban minerals. In the local arrangement around the unoccupied MX site, the neighboring (As3+O3) groups project their associated stereoactive lone-pairs of electrons into the channel. Where the MX site is occupied by Mn, there are six lone-pairs of electrons pointing toward Mn; the 18-electron rule predicts/rationalizes formulae for this stable transition-metal cluster. The (As3+O3) groups and MX occupant form a [Mn+(As3+O3)6] arrangement in accord with the 18-electron rule where Mn+ contributes 6 3d electrons and the six lone-pairs of the [(As3+O3)6] arrangement contribute 12 electrons for a total of 18 electrons that form nine molecular orbitals that are metal-ligand bonds or non-bonding. Magnussonite and dixenite, another basic manganese-iron arsenate-arsenite-silicate mineral of the Långban-type deposits in Bergslagen, Sweden, are the only two minerals known with such local [M+(As3+O3)n] transition-metal clusters. The presence of these exotic clusters in structures containing densely packed Mn2+ octahedra is not understood at present. [ABSTRACT FROM AUTHOR]

The excess electron containing compounds have exceptional initial hyper polarizabilities (σ), making them promising nominees for next generation non-linear optical materials. We investigated the geometric, thermodynamic, electrical, and nonlinear optical aspects of a highly strained, theoretically designed metallic cluster (MC), (Fe3Se2(CO)8, in this paper. The designed MC was thermally stable. Estimated ionization energy was used to characterize electrical stability nature (IE). Moreover, the significantly reduced EH–L values reflected the MC with its outstanding characteristics. The maximum absorption (λmax) for computed absorption of electronic transitions was estimated between 327 nm and 340 nm and HOMO → LUMO transitions were found to be the dominant electronic transition band in the UV–Vis spectral region. When comparing to the excited spectrum, the stimulated spectrum appeared to be substantially blue-shifted, with a wide band between 400 and 700 nm. It had the hyperpolarizability values of up to 4.3 × 104 au, resulting in a significant drop in excited state and higher hyperpolarizability values. Using the traditional two-level model, the resulting first hyperpolarizability was also explained. In this MC, the projections of hyperpolarizability on dipole moment coincided with overall hyperpolarizability, showing unidirectional charge transfer with polarizability at four basis sets (B3LYP, CAM-B3LYP, WB97XD and PBEPBE). The static second hyperpolarizability (β) value of the examined MC was higher. The recent discovery, we feel, can provide inspiration for further research into alternative excess electron first row transition MC for NLO applications.

Third-order nonlinear optical properties exhibited by Platinum nanoclusters and Gold nanoparticles integrated in a two-stage configuration are reported. Comparative nanostructures were nucleated in a monolithic complex platform form based on a single matrix by a dual ion-implantation process and a reduction in the ablation threshold from 2.2 J/cm2 to 1.2 J/cm2 was obtained. This modification in the photothermal response exhibited by the nanoparticles seems to derive from a fractional transfer of energy. Femtosecond z-scan measurements at 800 nm revealed a strong two-photon absorption in the dual-implanted sample together to an ultrafast electronic nonlinearity responsible for a self-defocusing effect. These findings highlight the potential for tailoring quantum systems by integration of hybrid photonic circuits using multi-implantation processes.

The crystal structure of magnussonite, ideally Mn2+18[As3+6(Mn1+x)O18]2[(H2O, Clx, ☐) (H2O, ☐)]2, from Långban, Sweden, was refined to an R1-index of 1.19% and the structure proposed by Moore and Araki (1979) is confirmed. Magnussonite has a densely packed structure of (Mnφn) polyhedra, φ = (O2−, H2O, Cl−), and (As3+O3) triangular pyramids that is best envisaged as layers of polyhedra in the same way as many of the other manganese-arsenite-arsenate structures from Långban. There are two distinct layers in magnussonite; the two layers may be combined into a slab that stacks along the a-direction with rotations between adjacent slabs. A surprising feature of the dense-packed magnussonite atomic arrangement is an array of structural channels along [111] that contain much of the disorder that occurs in the magnussonite structure. The channels contain the partly occupied MX site on the central axis of the channel, and the CLW2 site (with extremely low occupancy), also on the central axis of the channel. The CLW2 site, previously unrecognized in the magnussonite structure, contains H2O, whereas the minor Cl in the structure resides in the CLW1 channel site, balancing the charge of the MX-site occupant. The MX site on the central axis of the channels displays a coordination known only in Långban minerals. In the local arrangement around the unoccupied MX site, the neighboring (As3+O3) groups project their associated stereoactive lone-pairs of electrons into the channel. Where the MX site is occupied by Mn, there are six lone-pairs of electrons pointing toward Mn; the 18-electron rule predicts/rationalizes formulae for this stable transition-metal cluster. The (As3+O3) groups and MX occupant form a [Mn+(As3+O3)6] arrangement in accord with the 18-electron rule where Mn+ contributes 6 3d electrons and the six lone-pairs of the [(As3+O3)6] arrangement contribute 12 electrons for a total of 18 electrons that form nine molecular orbitals that are metal-ligand bonds or non-bonding. Magnussonite and dixenite, another basic manganese-iron arsenate-arsenite-silicate mineral of the Långban-type deposits in Bergslagen, Sweden, are the only two minerals known with such local [M+(As3+O3)n] transition-metal clusters. The presence of these exotic clusters in structures containing densely packed Mn2+ octahedra is not understood at present.

The DFTB theory was combined with the isothermal Brownian‐type molecular dynamics (MD) and metadynamics molecular dynamics (MMD) algorithms to perform simulation studies for Au clusters. Two representative DFTB parametrizations were investigated. In one parametrization, the DFTB‐A, the Slater–Koster parameters in the DFTB energy function were determined focusing on the ionic repulsive energy part, Erep and the other, the DFTB‐B, due attention was paid to the electronic band‐structure energy part, Eband. Minimized structures of these two parametrizations were separately applied in MD and MMD simulations to generate unbiased and biased trajectories in collective variable (CV) space, respectively. Here, we found the MD simulations monitored at 300 K manifest fluxional characteristics in planar cluster Au9/DFTB‐A, but give no discernible tracts of fluxionality for planar Au8/DFTB‐A and Au8/DFTB‐B, for nonplanar Au10/DFTB‐A and, to some extent, for nonplanar Au9/DFTB‐B; they are plausibly being hindered by higher‐than kBT energy barriers. Very recent FIR‐MPD spectroscopy measurements, however, were reported to have detected at 300 K both the planar and nonplanar neutral Aun clusters in the size range 5 ≤ n ≤ 13. The failure of MD simulations has prompted us to apply the MMD simulation and construct the free energy landscape (FEL) in CV space. Through scrutinizing the FELs of these clusters and their associated structures, we examine the relative importance of Erep/DFTB‐A and Eband/DFTB‐B in unraveling the covalent‐like behavior of valence electrons in Aun. Most important of all, we shall evaluate the DFTB parametrization in MMD strategy through comparing extensively the simulation data recorded with the gas‐phase experimental data. [ABSTRACT FROM AUTHOR]

Pd+ ions (90 keV) were implanted at normal incidence and at room temperature in different highly insulating (>200 GΩ) thermoplastic polymers (poly(methyl methacrylate), polypropylene, polyethylene terephthalate glycol-modified, and polycarbonate). At high fluence and optimized process parameters, the ion implantation gives rise to the formation of a nanocomposite thin surface layer constituted by Pd nanoclusters and carbonaceous material (nanographite/amorphous carbon). The morphological, microstructural, and microanalytical properties of the nanocomposite layers were investigated by He-ion microscopy, glancing incidence X-ray diffraction, and Raman scattering, respectively. The electrical properties were characterized by resistance, van der Pauw, and Hall measurements. We performed accurate simultaneous deformation/bending experiments and electrical resistance measurements. We show that the electrical resistance varies linearly with the mechanical deformation (beam deflection) applied. The experimental results are interpreted by "hopping conductivity" model considering the nanostructure configuration of the nanocomposite layers. A gauge factor in the range between 4 and 8, depending on the ion-implanted polymer, was obtained for prototype strain gauge devices. [ABSTRACT FROM AUTHOR]

Statistical analysis of the results of molecular dynamics (MD) calculation of gas-phase "self-assembling" of nanoclusters during metal vapor condensation revealed the laws of energy transfer between metallic clusters and inert gas atoms. A model is proposed to determine the parameters of heat exchange between clusters and the environment at the initial stage of condensation. This model is based on averaged MD data on the interaction between small clusters and argon atoms. The parameters that can be used to transfer information from MD to a macroscopic condensation model are numerically determined. The results obtained can be used to describe nucleation to predict a nanoparticle size distribution in the production of metallic powders. [ABSTRACT FROM AUTHOR]

A computing scheme for a mesoscopic description of a nucleation process has been built using a statistical analysis of the results of molecular dynamics simulation of a supersaturated metallic vapor. The parameters that enter into equations for cluster growth rate and heat release during condensation are found by a direct statistical computation in a molecular dynamics method. The rates of cluster formation calculated by a molecular dynamics method agree well with the numerical model developed in this work. [ABSTRACT FROM AUTHOR]

Nanoparticles can be used in a large variety of applications, including magnetic sensing, biological, superconductivity, tissue engineering, and other fields. In this study, we explore the fabrication of gas phase silver nanoparticles using a sputtering evaporation source. This setup composed of a dual magnetron cluster source holds several advantages over other techniques. The system has independent control over the cluster concentration and a wide range of cluster size and materials that can be used for the clusters and for the matrix where it can be embedded. Characterization of these silver nanoparticles was done using transmission electron microscopy (TEM). We obtain a lateral width of 10.6 nm with a dispersion of 0.24 nm. With atomic force microscopy (AFM) a Gaussian fit of this distribution yields and average height of 6.3 nm with a standard deviation of 1.4 nm. We confirm that the deposited silver nanoparticles have a homogenous area distribution, that they have a defined shape and size distribution, and that they are single standing nanoparticles. Given that the scientific literature is not precise regarding the toxic concentration of the nanoparticles, devices such as ours can help clarify these questions. In order to explore further biological applications, we have done preliminary experiments of cell spreading (myoblast adhesion), obtaining interesting morphological changes correlated with the silver concentration on the surface. With a deposited silver concentration ranging from 100⁻620 ng/cm2, the cells showed morphological changes in a short time of 2 h. We conclude that this high precision nanoparticle fabrication technique is adequate for further biological research.

The Fischer-Tropsch reaction is initiated by direct CO dissociation for Iron catalyst even though a H-assisted mechanism may be easier on other metals. In the gas phase, the CO dissociation is only favorable for Fe-clusters composed by more than 11 atoms. We show here the remarkable effect of the support TiO 2 (1 1 0), making this dissociation exothermic for Fe 4 and Fe 5 clusters. The main factor for the CO activation is the electron transfer to the reducible support. The role of the TiO 2 (1 1 0) support is to transform the neutral cluster into a positively charged one for which CO dissociation is easier. [ABSTRACT FROM AUTHOR]

In terms of the model of stable jellium, self-consistent calculations of spatial distributions of electrons and potentials, as well as of energies of dissociation, cohesion, vacancy formation, electron attachment, and ionization potentials of solid clusters of Mg, Li (with N ≤ 254 ) and of clusters containing a vacancy ( N ≥ 12) have been performed. The contribution of a monovacancy to the energy of the cluster and size dependences of its characteristics and of asymptotics have been discussed. Calculations have been performed using a SKIT-3 cluster at Glushkov Institute of Cybernetics, National Academy of Sciences, Ukraine (Rpeak = 7.4 Tflops). [ABSTRACT FROM AUTHOR]

Metallic clusters have been widely studied due to their special electrical, optical, and catalytic properties. The many-body Gupta potential is applied to describe the interatomic interaction of Ni, Cu, Ag, Au, Pd, and Pt clusters, and their global minimal structures within 100 atoms are optimized using dynamic lattice searching (DLS) method. The configurational distribution of global minima is analyzed, and the geometrical difference among these clusters is demonstrated. Results show that the dominant motif of Ni and Cu clusters is the icosahedron, and in Ag and Au clusters the number of decahedra is slightly larger than that of the icosahedra. However, more face-centered cubic (fcc), stacking fault fcc, and amorphous structures are formed in Au clusters than in Ag clusters. Furthermore, the main motif of Pd and Pt clusters is the decahedron. In particular, Ni adopts a Leary tetrahedral motif, and Pt is a central vacant icosahedron. The difference related to the potential parameters of these metallic clusters is further investigated by energy analysis. Moreover, the potential energy surfaces (PES) of 38-atom metallic clusters is characterized in terms of conformational analysis. It was found that the sequence of the number of local minima on the PES from large to low is Ni, Cu, Ag, Pt, Pd, and Au. [ABSTRACT FROM AUTHOR]

In this work we use magnetic deflection of V, Nb, and Ta atomic clusters to measure their magnetic moments. While only a few of the clusters show weak magnetism, all odd-numbered clusters deflect due to the presence of a single unpaired electron. Surprisingly, for the majority of V and Nb clusters an atomic-like behavior is found, which is a direct indication of the absence of spin–lattice interaction. This is in agreement with Kramers degeneracy theorem for systems with a half-integer spin. This purely quantum phenomenon is surprisingly observed for large systems of more than 20 atoms, and also indicates various quantum relaxation processes, via Raman two-phonon and Orbach high-spin mechanisms. In heavier, Ta clusters, the relaxation is always present, probably due to larger masses and thus lower phonon energies, as well as increased spin–orbit coupling.

Abstract: X-ray photoelectron spectroscopy and transmission electron microscopy have been used to investigate the nature and characteristics of oxygen deficient gallium oxide films grown by pulsed laser deposition. The presence of the Ga3+ and Ga+ oxidation states, together with metallic Ga0 was observed by XPS in Ga2O2.3 sub-oxide films. TEM images reveal the presence in a Ga2O3 matrix of gallium oblong particles whose structure studied at nitrogen temperature was found to correspond to the β monoclinic phase of metallic gallium. These results characterize the formation of nanocomposite films with Ga metallic clusters embedded in a stoichiometric Ga2O3 matrix. The nanocomposite film formation is due to a phase separation in the metastable sub-stoichiometric Ga2O2.3 film. [Copyright &y& Elsevier]

Substantiated method determining the distribution of metal particle size on the optical absorption data for composites consisting of dielectric medium and metallic inclusions and tested this method on hydrosols of gold nanoparticles compared to the data obtained by microscopic examination. [ABSTRACT FROM AUTHOR]

Abstract: The dipole moments of Na n clusters in the size range 10< n <20, recently measured at very low temperature (20K), are much smaller than predicted by standard density functional methods. On the other hand, the calculated static dipole polarizabilities in that range of sizes deviate non-systematically from the measured ones, depending on the employed first principles approach. In this work we calculate the dipole moments and polarizabilities of a few isomers of Na n clusters of selected sizes (n =13, 14, 16), obtained recently through an extensive unbiased search of the global minimum structures, and using density functional theory methods as well as ab initio MP2, CASSCF, and MR-CI methods. Among the density functional approaches, we consider the usual local density and generalized gradient approximations, as well as a recent van der Waals self-consistent functional accounting for non-local dispersion interactions. Both non-local pseudopotentials and all-electron implementations are employed and compared in order to assess the possible contribution of the core electrons to the electric dipole moments. Our new geometries possess significantly smaller electric dipole moments than previous density functional results, mostly when combined with the van der Waals exchange–correlation functional. However, although the agreement with experiment clearly improves upon previous calculations, the theoretical dipole moments are still about one order of magnitude larger than the experimental values, suggesting that the correct global minimum structures have not been located yet. [Copyright &y& Elsevier]

Abstract: A magnetron-sputtering (MagS) cluster source was used to produce metal clusters of different size distributions by varying individual source parameters. Selectivity of the size of the Al clusters was observed and the mass distribution presents wide-range controllability by the MagS-source, which enables experimental determination of the growth process of Al clusters. By implementing the extended Smoluchowski rate equation, here we propose an interpretation of the cluster-growth kinetics in the gas phase environment. A collision-dependent growing time domain is demonstrated. [Copyright &y& Elsevier]

Abstract: Highly non-stoichiometric indium tin oxide (ITO) thin films were grown by pulsed energy beam deposition (pulsed laser deposition-PLD and pulsed electron beam deposition-PED) under low oxygen pressure. The analysis of the structure and electrical transport properties showed that ITO films with a large oxygen deficiency (more than 20%) are nanocomposite films with metallic (In, Sn) clusters embedded in a stoichiometric and crystalline oxide matrix. The presence of the metallic clusters induces specific transport properties, i.e. a metallic conductivity via percolation with a superconducting transition at low temperature (about 6K) and the melting and freezing of the In–Sn clusters in the room temperature to 450K range evidenced by large changes in resistivity and a hysteresis cycle. By controlling the oxygen deficiency and temperature during the growth, the transport and optical properties of the nanocomposite oxide films could be tuned from metallic-like to insulating and from transparent to absorbing films. [Copyright &y& Elsevier]

We examine the interaction of short and intense femtosecond laser field with Kr clusters contained ( ∼107atoms). Efficient heating of the cluster by laser is followed by rapid expansion of the cluster and leads to his final explosion. We have used the modified nanoplasma model (by adding tne the term of electron surface collision frequency in the expression of the electron-ion collision frequency) for the study of the interaction of an intense laser field with large Kr clusters, and have found that the hydrodynamic pressure is larger than the coulomb one and the electron energy of electrons after the pulse is passed is found of order of 2.5keV. [ABSTRACT FROM AUTHOR]

Abstract: An influence of metallic clusters on the optical absorption and phonon spectra of crystals was studied. Metallic clusters of spherical shape were formed during the growth of non-stoichiometric crystals. Radii of clusters are in range from 10 to 500nm according to scanning electron microscopy (SEM) data. The density of clusters was estimated from fractal dimension calculations. The fractal dimension of clusters has been found to be varied from 1.488 to 1.793. In the framework of Mie theory the spectral and size dependencies of extinction coefficients were calculated. From the experimentally obtained spectra it is evident that the metallic clusters are responsible for the bands in the transparency region of crystals (360–430nm) and for the peaks in the mid-infrared absorption spectra which are not present in the spectra of pure cadmium iodide. The nature of this additional optical and infrared absorption is concerned with the bulk and surface plasmons and the surface phonon modes of metallic clusters, respectively. [Copyright &y& Elsevier]

Abstract: We present a theoretical study of embedded in- and on the surface of a rare-gas droplet. We describe the active electrons of the cluster using time-dependent density functional theory, while the surrounding Ar atoms are treated by classical molecular dynamics of polarizable atoms. Like for neutral clusters, we found that the surrounding material modifies noticeably the optical properties of compared to the free cluster. Ar polarization and core repulsion act in opposite directions, so that the actual line shift depends significantly on the trapping site. We show that the long range monopole-dipole coupling between a charged cluster and a polarizable matrix makes more likely to be embedded inside the Ar matrix, while small neutral Na clusters are more likely to be trapped at the surface. [Copyright &y& Elsevier]

The Gupta-type many-body potential was applied to describe the interactions between atoms in zinc nanoclusters. From the calculated ground state structures, obtained by Brownian-type molecular dynamic simulation, we investigated the temperature effect of zinc clusters. We studied in particular the constant volume specific heat CV which is a thermodynamic quantity and also the relative bond length Lindemann parameter d which is a geometric quantity. Effort is devoted to revealing the anomalies observed in these quantities for Zn clusters and making a comparison with those of the typical sp-type metallic clusters. To this end, we have chosen to calculate the CV and d of clusters Znn for 29, 33, and 53 which are judged to be less stable by the energy difference and the second energy difference as well as 6, 36, 42, and 49 which are judged by the same energy criteria to be relatively more stable. Our results of simulation show that the structures of CV and d exhibit unusual phase transition behaviors which are drastically different from those of the usual metallic clusters. General scenarios observed in the simulation are the prevalence of the pre-melting phenomenon predicted in all of the clusters studied here. [ABSTRACT FROM AUTHOR]

The structure and electrical properties of laser-ablated LaSrMnO thin films containing mesoscopic clusters with metallic conductivity in an insulator matrix were studied. It is shown that the film properties, including temperature dependence of magnetoresistance and its behavior in high magnetic field, display features typical for spin-dependent tunneling. [Copyright &y& Elsevier]

[Display omitted] • Ground state structures were obtained from BOMD and DFT calculations. • The Li 12 Y system is a new superatom with a high magnetic moment and exchange splitting with icosahedral geometry. • (Li 12 Y) 2 dimer preserves the energetic and magnetic stability. • The Boltzmann distribution shows the dependence between magnetic properties and temperature. A study was carried out to determine the structural, energetic, and magnetic properties of lithium clusters doped with yttrium, including Born − Oppenheimer molecular dynamics under the Density Functional Theory framework. The study considered the ZORA model for the scalar relativistic effects due to the presence of the yttrium atom. The Li 12 Y system was identified as a new superatom with icosahedral geometry, high magnetic moment, and exchange splitting. The interactions of the sp -Li orbitals with the 4d -Y orbitals are fundamental to understand the effects on the studied properties. The spin density was concentrated over the yttrium atom regardless of the size of the cluster. Furthermore, the energetic integrity of the Li 12 Y is preserved in the (Li 12 Y) 2 dimer, attesting to its potential as a magnetic building block for nanostructured materials. Additionally, the effect of temperature on the magnetic moment in the context of classical Boltzmann distribution was explored, finding a dependence between magnetic properties and temperature. [ABSTRACT FROM AUTHOR]