Polyatomic Clusters Research Articles

Structural and Chemical Diversity and Complexity of Sulfur Minerals

The chemical and structural diversity of minerals containing sulfur as an essential mineral-forming element has been analyzed in terms of the concept of mineral systems and the information-based structural and chemical complexity parameters. The study employs data for 1118 sulfur mineral species approved by the International Mineralogical Association. All known sulfur minerals belong to nine mineral systems, with the number of essential components ranging from one to nine. The chemical and structural complexity of S minerals correlate with each other; that is, on average, chemical complexification results in structural complexification. The minerals with S–O bonds (sulfates and sulfites) are more complex than those without S–O bonds (sulfides and sulfosalts). However, the most complex sulfur mineral known so far is incomsartorite, Tl6Pb144As246S516, a sulfosalt. The complexity-generating mechanism in sulfides and sulfosalts is the complex combination of different modules excised from parent PbS or SnS archetypes with the subsequent formation of superstructures. The drivers for structural complexity in sulfates are more diverse and, in addition to modular construction and superstructures, also include a high hydration state, the presence of polyatomic clusters, and framework complexity. The most complex Martian minerals are most probably halotrichite-group minerals. The chemical and structural complexity increases with the passage of geological time with the formation of the most complex sulfosalts at Lengenbach (Swiss Alps) triggered by life (activity of sulfur-reducing bacteria).

Mode‐Selective Vibrational‐Tunneling Dynamics in theN=2 Triad of the Hydrogen‐Bonded (HF)2Cluster

AbstractRovibrationally resolved spectra of theNj=22,Ka=0←1 transition and of theNj=23,Ka=0←0 andKa=1←0 transitions of the hydrogen‐bonded (HF)2have been measured in the near infrared range near 1.3 μm by cw‐diode laser cavity ring‐down spectroscopy in a pulsed supersonic slit jet expansion. The spectroscopic assignment and analysis provided an insight into the dynamics of these highly‐excited vibrational states, in particular concerning the predissociation of the hydrogen bond and the tunneling process of the hydrogen bond switching. Together with our previously analyzed spectra of theNj=21andNj=22components, the mode‐specific dynamics in all three components of this triad can now be compared. In theN=2 triad, the HF‐stretching vibration is excited by two quanta with similar excitation energy, but the quanta are distributed in three different ways, which has a distinct influence on the dynamics. The observed band centers and tunneling splittings are in agreement with our recent calculations on the (HF)2potential energy hypersurface SO‐3, resolving the long‐standing discussion about the symmetry ordering of polyad levels in this overtone region. The results are also discussed in relation to the general questions of non‐statistical reaction dynamics of polyatomic molecules and clusters and in relation to quasi‐adiabatic channel above barrier tunneling.

Anisotropically Fused Clusters Form a 2D Superatomic Sheet Exhibiting Polarized Light Emission

Polarized light emission is desirable for a number of optoelectronic applications and is difficult to realize in conventional semiconductors. Here we take advantage of the tunability in structure, symmetry, and functionality of superatomic semiconductors, i.e., crystalline arrays of atomically precise polyatomic clusters. We report the in-plane anisotropy in electronic and optical properties in the van der Waals two-dimensional (2D) superatomic semiconductor CsRe6Se8I3. Consistent with structural anisotropy within the 2D plane, CsRe6Se8I3 shows linearly polarized photoluminescence (PL) emission at room temperature. By lowering the temperature, we observe a new PL peak with nearly orthogonal linear polarization without an accompanying structural phase transition. Theoretical calculations together with spectroscopic measurements suggest that the high- and low-temperature PL peaks originate, respectively, from direct and indirect excitons. These results demonstrate rich optical properties of superatomic solids, which may be precisely programmed with the hierarchical design of the constituent clusters and the intercluster bonding.

Recent Progress in Computational Design of Single-Atom/Cluster Catalysts for Electrochemical and Solar-Driven N2 Fixation

Fixation of dinitrogen into ammonia is an essential biological process for the evolution of life, and at the same time ammonia is an essential component for many industrial processes, including fertilizers, plastics, and so on. NH3 is also known as the best alternative to H2 in fuel cells. However, due to chemical inertness, direct conversion of N2 into NH3 is not possible; a suitable catalyst is required. The century-old Haber–Bosch process, utilizing an Fe-based catalyst, is extremely energy-intensive and eco-unfriendly due to the consumption of fossil fuels. In recent years, huge development has taken place in the design and applications of suitable electro- and photocatalysts for artificial N2 fixation. First-principles calculations have been considered as a powerful avenue for theoretical screening of promising catalysts through rational design and analysis of the plausible mechanisms or pathways of reactions. The present review focuses on recent theoretical developments of various unsupported nanoclusters and supported single-atom and cluster catalysts for application in electro- and photochemical N2 reduction reactions. The support substrates include oxides, carbides, nitrides of metal-based 2D materials, porous carbonaceous materials, and metal-free 2D materials containing main-group elements like B, C, N, and P. Although some reviews have already been made, focusing on the research related to either electro- or photocatalytic N2 fixation on different catalysts, here we give a comprehensive account of both electrochemical and photochemical nitrogen reduction reaction (NRR) activities and selectivities of various supported single-atom and polyatomic cluster catalysts. Additionally, a comparative assessment is made on the basis of free energy of adsorption, most favorable pathway, potential limiting step, and corresponding limiting potential of the NRR.

Towards advanced complex quantum materials for spin-related applications and photo-induced heterogeneous catalysis: The case of (Fen)@g-CN1 (n = 2,3) and (Mn)@(g-CN1)2

Perspective heterostructures based on Fe and Mn adatoms on 2D g-C3N4 films of different morphology were designed and investigated by means of DFT GGA/PBE and GGA/HSE levels of theory. Spontaneous spin polarization of g-C3N4 and a variety of electronic properties were theoretically investigated. It was found that GGA HSE DFT potential is suitable to describe the main properties of g-C3N4-based heterostructures with transition metal adatoms. It was revealed that (Mn)@(g-CN1)2 heterostructure is a half-metal with 0.5 eV band gap in α-channel. (Fen)@g-CN1, n = 2,3) demonstrate different semiconducting properties which are determined by structure and number of Fe adatoms in the unit cells. The presence of several independent centers of Fe forming polyatomic clusters was stated as one of the interests in catalysis. It was found that all considered heterostructures may serve as perspective quantum materials in different spin-related applications.

Signature of the neighbor's quantum nuclear dynamics in the electron transfer mediated decay spectra.

We computed fully quantum nuclear dynamics, which accompanies electron transfer mediated decay (ETMD) in weakly bound polyatomic clusters. We considered two HeLi2 clusters – with Li2 being either in the singlet electronic ground state or in the triplet first excited state – in which ETMD takes place after ionization of He. The electron transfer from Li2 to He+ leads to the emission of another electron from Li2 into the continuum. Due to the weak binding of He to Li2 in the initial states of both clusters, the involved nuclear wavepackets are very extended. This makes both the calculation of their evolution and the interpretation of the results difficult. We showed that despite the highly delocalized nature of the wavepackets the nuclear dynamics in the decaying state is imprinted on the ETMD electron spectra. The analysis of the latter helps understanding the effect which electronic structure and binding strength in the cluster produce on the quantum motion of the nuclei in the decaying state. The results produce a detailed picture of this important charge transfer process in polyatomic systems.

Ion association in hydrothermal aqueous NaCl solutions: implications for the microscopic structure of supercritical water.

Knowledge of the microscopic structure of fluids and changes thereof with pressure and temperature is important for the understanding of chemistry and geochemical processes. In this work we investigate the influence of sodium chloride on the hydrogen-bond network in aqueous solution up to supercritical conditions. A combination of in situ X-ray Raman scattering and ab initio molecular dynamics simulations is used to probe the oxygen K-edge of the alkali halide aqueous solution in order to obtain unique information about the oxygen's local coordination around the ions, e.g. solvation-shell structure and the influence of ion pairing. The measured spectra exhibit systematic temperature dependent changes, which are entirely reproduced by calculations on the basis of structural snapshots obtained via ab initio molecular dynamics simulations. Analysis of the simulated trajectories allowed us to extract detailed structural information. This combined analysis reveals a net destabilizing effect of the dissolved ions which is reduced with rising temperature. The observed increased formation of contact ion pairs and occurrence of larger polyatomic clusters at higher temperatures can be identified as a driving force behind the increasing structural similarity between the salt solution and pure water at elevated temperatures and pressures with drawback on the role of hydrogen bonding in the hot fluid. We discuss our findings in view of recent results on hot NaOH and HCl aqueous fluids and emphasize the importance of ion pairing in the interpretation of the microscopic structure of water.

4O10Cd Clustering in ZnBVI-Rich CdxZn1−xOyBVI1−y (BVI = S, Se, Te) Highly Lattice-Mismatched Alloys

Clustering of highly lattice-mismatched semiconductor alloys has attracted considerable interest recently. However, strong internal strains and cluster variety are the main disadvantages of such alloys. Zinc blende ZnBVI-rich CdxZn1−xOyB1−yVI (BVI = S, Se, Te) with 4O10Cd identical clusters are proposed to resolve these problems. The decrease in the internal strains is a cause of the cluster formation in ZnS- and ZnSe-rich alloys. The favorable CdO and ZnTe bonding is an additional reason for the cluster occurrence in ZnTe-rich alloys. The cohesive energies of CdSe and ZnSe, stiffness coefficients, bond stretching and bond bending elastic constants of CdSe are calculated. The majority of Cd and oxygen atoms should be in 4O10Cd clusters up to 800°C if the ZnS- and ZnSe-rich alloy contents are, respectively, y ≥ 2.5 × 10−4 and y > 3 × 10−4, and x ≈ 2.5y. The obtained results demonstrate that CdxZn1−xOyB1−yVI materials are promising semiconductors with significantly reduced internal strains and identical polyatomic clusters containing oxygen tetrahedrons.

Influence of the Finite-Size Effect on the Cluster Ion Emission of Silicon Nanostructures

The finite-size effect increasing the emission of polyatomic cluster ions from silicon nanostructures as compared to a macroscopic sample has been studied. This study has been performed for the first time in periodic structures with 10- and 50-nm-wide combs fabricated by electron beam lithography with subsequent plasma chemical etching. It has been shown that the yield of polyatomic cluster ions from structures with the comb whose effective width is comparable with the projective range of a bombarding bismuth ion in silicon is much higher than the yield from macroscopic samples, e.g., by more than a factor of 5 for 28Si10− (m/z = 280). This effect has been explained by a partial limitation of dissipation channels for the energy released by the bombarding ion in the volume of the structure, which stimulates a more efficient development of nonlinear collision cascades in such a volume and, as a result, increases the yield of polyatomic cluster ions.

Nonlinear optical properties of tellurium oxide nanoclusters

The finite field method using ab initio hybrid functional approach was applied to estimate nonlinear properties of the cluster based on paratellurite crystal structure. The good agreement was found with previously reported data.The method demonstrate high efficiency in prediction of nonlinear properties for a wide ensemble of sufficiently large polyatomic clusters.

Clustering in ZnBVI-rich SrxZn1−xOyBVI1−y (BVI = S, Se, Te) highly mismatched alloys

Abstract The clustering properties of dilute highly mismatched semiconductor alloys attract considerable interest recently. Non-homogeneity of clusters and strong internal strains are the main disadvantages of such alloys. 4O10Sr clustering in ZnBVI-rich SrxZn1−xOyBVI1−y (BVI = S, Se, Te) up to 800 °C are presented. Reduction of the internal strains is a cause of the cluster formation. The cohesive energies, stiffness coefficients, bond stretching and bond bending elastic constants of zinc blende SrS and SrSe are estimated. All or almost all oxygen atoms should be in 4O10Sr clusters up to 800 °C in SrxZn1−xOyS(Se)1−y if alloy content is y > 1 × 10−3 (5 × 10−4) and x > 4y. SrxZn1−xOyTe1−y are completely 4O10Sr cluster ordered with contents from the ultra dilute limit (x > 1 × 10−4, y = 1 × 10−4) up to 800 °C. The densities of 4O10Sr clusters were calculated by minimization of the free energy. The binding energy of the electron bound to the oxygen tetrahedron in ZnTe:O at RT is estimated. The obtained results demonstrate that SrxZn1−xOyBVI1−y are promising semiconductors with the reduced internal strains and identical polyatomic clusters containing oxygen tetrahedrons.

Exceptionally Complex Electronic Structures of Lanthanide Oxides and Small Molecules.

Lanthanide (Ln) oxide clusters and molecular systems provide a bottom-up look at the electronic structures of the bulk materials because of close parallels in the patterns of Ln 4fN subshell occupancy between the molecular and bulk Ln2O3 size limits. At the same time, these clusters and molecules offer a challenge to the theory community to find appropriate and robust treatments for the 4fN patterns across the Ln series. Anion photoelectron (PE) spectroscopy provides a powerful experimental tool for studying these systems, mapping the energies of the ground and low-lying excited states of the neutral relative to the initial anion state, providing spectroscopic patterns that reflect the Ln 4fN occupancy. In this Account, we review our anion PE spectroscopic and computational studies on a range of small lanthanide molecules and cluster species. The PE spectra of LnO- (Ln = Ce, Pr, Sm, Eu) diatomic molecules show spectroscopic signatures associated with detachment of an electron from what can be described as a diffuse Ln 6s-like orbital. While the spectra of all four diatomics share this common transition, the fine structure in the transition becomes more complex with increasing 4f occupancy. This effect reflects increased coupling between the electrons occupying the corelike 4f and diffuse 6s orbitals with increasing N. Understanding the PE spectra of these diatomics sets the stage for interpreting the spectra of polyatomic molecular and cluster species. In general, the results confirm that the partial 4fN subshell occupancy is largely preserved between molecular and bulk oxides and borides. However, they also suggest that surfaces and edges of bulk materials may support a low-energy, diffuse Ln 6s band, in contrast to bulk interiors, in which the 6s band is destabilized relative to the 5d band. We also identify cases in which the molecular Ln centers have 4fN+1 occupancy rather than bulklike 4fN, which results in weaker Ln-O bonding. Specifically, Sm centers in mixed Ce-Sm oxides or in SmxOy- (y ≤ x) clusters have this higher 4fN+1 occupancy. The PE spectra of these particular species exhibit a striking increase in the relative intensities of excited-state transitions with decreasing photon energy (resulting in lower photoelectron kinetic energy). This is opposite of what is expected on the basis of the threshold laws that govern photodetachment. We relate this phenomenon to strong electron-neutral interactions unique to these complex electronic structures. The time scale of the interaction, which shakes up the electronic configuration of the neutral, increases with decreasing electron momentum. From a computational standpoint, we point out that special care must be taken when considering Ln cluster and molecular systems toward the center of the Ln series (e.g., Sm, Eu), where treatment of electrons explicitly or using an effective core potential can yield conflicting results on competing subshell occupancies. However, despite the complex electronic structures associated with partially filled 4fN subshells, we demonstrate that inexpensive and tractable calculations yield useful qualitative insight into the general electronic structural features.

The tunable luminescent property and wide band gap in three 1D hybrid templated borates containing different metallic ions and oxoboron clusters

Our systematic exploration of chainlike borate in the hybrid templated borate systems has led to three new borates, namely, [GaTETA]·[B5O8(OH)2]·H2O, [InTETA]·[B5O8(OH)2]·1.5H2O, and [Cd(1,2-dap)]·[B6O11(OH)2]·H2O. The structures of the three borates were determined by single-crystal X-ray diffraction. [Cd(1,2-dap)]·[B6O11(OH)2]·H2O represents the first example of chainlike borate containing Cd2+ transition metal cations and [B6O11(OH)2] cluster. [GaTETA]·[B5O8(OH)2]·H2O is isostructural with [InTETA]·[B5O8(OH)2]·1.5H2O, whose structure features a one-dimensional (1D) polyatomic chain constructed of MO2N4 octahedron and [B5O8(OH)2] groups, such chains are further bridged by HBs resulting in a three-dimensional (3D) supermolecular network. Optical and luminescent property measurements have also been performed on the three compounds. Only fluorescence intensity of [GaTETA]·[B5O8(OH)2]·H2O decreased fiercely with temperature increase. Besides, the band gap of [GaTETA]·[B5O8(OH)2]·H2O and its isomer [InTETA]·[B5O8(OH)2]·1.5H2O and [Cd(1,2-dap)]·[B6O11(OH)2]·H2O are very distinct from each other, it may indicate that optical and luminescent property of hybrid borate can be manipulated by adjusting of polyatomic cluster and metallic ion.

A mass-selective ion transfer line coupled with a uniform supersonic flow for studying ion-molecule reactions at low temperatures.

A new approach based on the uniform supersonic flow technique-a cold, thermalized de Laval expansion offering the advantage of performing experiments with condensable species-has been developed to study ion-molecule reactions at low temperatures. It employs a mass-selective radio frequency transfer line to capture and select ions from an adaptable ionization source and to inject the selected ions in the core of the supersonic expansion where rate coefficients and product branching can be measured from room temperature down to ∼15 K. The transfer line incorporates segmented ion guides combining quadrupolar and octapolar field orders to maximize transmission through the differential apertures and the large pressure gradients encountered between the ionization source (∼mbar), the quadrupole mass filter (∼10-5 mbar), and the de Laval expansion (∼mbar). All components were designed to enable the injection of cations and anions of virtually any m/z ratio up to 200 at near ground potential, allowing for a precise control over the momentum and thermalization of the ions in the flow. The kinetics and branching ratios of a selection of reactions have been examined to validate the approach. The technique will be instrumental in providing new insight on the reactivity of polyatomic ions and molecular cluster ions in astrophysical and planetary environments.

Kinetic Spectra of Polyatomic Clusters Formed via the Ion Sputtering of Metals

A theory is developed for the ion sputtering of metals resulting in the formation of excited neutral and charged clusters with their subsequent fragmentation to a stable state. The effect fragmentation has on the kinetic spectra and charge state of clusters is considered. The results are presented in the form of convenient formulas. Calculations for the kinetic spectra of polyatomic clusters of niobium and silver are given as examples.

Determination of Single- and Multi-Component Nanoparticle Sizes by X-ray Absorption Spectroscopy

An approach to estimate the size of quasi-spherical nanoparticle systems composed of atoms crystalizing in face centered cubic lattice using the data from X-ray absorption spectroscopy is introduced. For monoatomic clusters, the number of atomic layers surrounding the X-ray-absorbing atom m is evaluated from the coordination numbers, and the size of the particle calculated as the diameter of a sphere having the same volume as the cuboctahedron with the edge length of m atoms, assuming complete atomic layer structure. The particle size estimated by the approach agrees well with the experimental data obtained by other methods for clusters up to 5 nm. For bimetallic systems, coordination numbers of one component to the other in various inner-structured mixtures were derived. The interatomic distance of the solid solution is approximated to the weighted mean of the two constituents’ lattice parameters and these mean values were used to estimate the particle size. The method could be applied to core-shell structures of bimetallic systems, as well as to three-component particles using reasonable approximations, and the particle sizes are estimated in a similar manner. The diameters of polyatomic clusters estimated by this approach were shown to closely follow the experimental data obtained by independent techniques.

Topology of Intermetallic Structures: From Statistics to Rational Design.

More than 38 000 substances made only of metal atoms are collected in modern structural databases; we may call them intermetallic compounds. They have important industrial applications, and yet they are terra incognita for most of our undergraduate students. Their structural complexity and synthesis are not easily adaptable to first years laboratories, keeping them away from the standard curricula. They have been described over the years following alternative and complementary views such as coordination polyhedra, atomic layers, and polyatomic clusters. All of these descriptions, albeit relying on grounded principles, have been applied on a subjective basis and never implemented as a strict computational algorithm. Sometimes, the authors generated multiple views of the same structure reported with beautifully drawn figures and/or photos of hand-crafted models in seminal works of the precomputer age. With the use of our multipurpose crystallochemical program package ToposPro, we explored the structural chemistry of intermetallics with objective and reproducible topological methods that allow us to reconcile different structure descriptions. After computing the connectivity patterns between the metal atoms on the basis of Voronoi partitioning of the crystal space, we were able to group the 38 000 intermetallic compounds into 3700 sets of crystal structures with the same topology of atomic net. We have described the different views used in the literature and shown that 12-vertex polyhedra are the most frequent (33%) and that almost half of them are icosahedron-like (46%), followed by cuboctahedron (25%) and, unexpectedly, by bicapped pentagonal prism (13%). Looking for layers, we have found that the hexagonal lattice, which corresponds to the closest packing of spheres on a plane, exists in more than 11 000 crystal structures, confirming the close-packed nature of intermetallics. We have also applied the nanocluster approach, which goes beyond the first coordination sphere and looks for structural units as multishell clusters that assemble the whole structure. This approach shows that 41% of intermetallics can be assembled with a single nanocluster and that 22.4% of these are packed according to the face-centered cubic motif of the closest packing of spheres in three-dimensional space. We have shown that our approach can easily adopt any other building model and hence could become a platform for a universal predictive scheme. Within this scheme, all of the structural descriptors can be related to experimental data and theoretical modeling results and then can be used to synthesize new intermetallic compounds and to foresee novel materials.

Gas-Phase Spectroscopic Detection and Structural Elucidation of Carbon-Rich Group 14 Binary Clusters: Linear GeC3Ge

Guided by high-level quantum-chemical calculations at the CCSD(T) level of theory, the first polyatomic germanium-carbon cluster, linear Ge2C3, has been observed at high spectral resolution in the gas phase through its remarkably complex fundamental antisymmetric C-C stretching mode ν3 located at 1932 cm(-1). The observation of a total of six isotopic species permits the derivation of a highly accurate value for the equilibrium Ge-C bond length. The present study suggests that many more Ge-C species might be detectable in the future using a combination of laser-ablation techniques for production and high-resolution infrared and/or microwave techniques for spectroscopic detection.

Equivalent lipophilicity of esterified unsaturated higher fatty acids in the presence of silver nanoclusters

Based on the own experimental data and the literature ones, a supposed relationship between the polarities of esterified unsaturated higher fatty acids contained in the native lipids in the presence of silver nanoclusters and possible variations in the coordination numbers of separate silver atoms in these clusters participating in the π-complex formation is described. Some new molecular parameters for satisfactory description of the chromatographic behavior and the general physicochemical characteristics of unsaturated hydrocarbon chains as constituents of individual lipid molecules in the presence of silver compounds are proposed. Some variants of possible applications of complex organic structures including their polyatomic clusters are mentioned.

Interatomic Coulombic decay in polyatomic rare-gas clusters

SynopsisA new method for a complete theoretical description of Interatomic Coulombic decay (ICD) in large polyatomic rare-gas clusters will be presented. This original method combines the projection-operator formalism of resonant scattering theory, the diatomics-in-molecules technique and a surface hopping algorithm. Such combined approach has fairly low computational costs and constitutes an efficient tool for studying ICD in polyatomic clusters. Benchmark examples will be given to illustrate the method. Results on ICD in large rare-gas clusters will finally be reported.