Metal Nitride Clusters Research Articles

Synthesisation, Fabrication, and Incorporation Techniques of MAX Phase and MXene Saturable Absorber in Passively Q-switched and Mode-locked All-fibre Laser Cavities: A Review

MAX phases and MXene have been introduced in passively pulsed-laser generation for their viability as substitutes to unadventurous saturable absorbers such as saturable absorber mirror, multi-wall and single-wall carbon nanotube, graphene, and transition metal dichalcogenides, contributing to both Q-switching and mode-locking tactics. Fundamental saturable-absorber features such as nonlinear saturable absorption, astonishing depth of modulation, flexibly tuneable bandgap, and high electron density around the Fermi level, establish MAX phases and MXene as formidable contenders with decent performance in the saturable absorber regime. Recent research works contributing to MAX Phases and MXene—particularly in nonlinear ultrafast optics—have shown an exponential increase, since MAX Phases and MXene are of the prime regime of 2D nanomaterials that offer vast combination options by the formation of metal nitride, metal carbide, or carbonitride clusters with a 2D layered structure, with special emphasis on fabrication and incorporation of saturable absorbers into laser cavities. This review critically summarises the advancement on the synthesis, fabrication, and incorporation of the MAX phases and MXene saturable absorbers, as well as the incorporation methodologies and techniques into all-fibre laser cavities configured either in linear or ring configuration, summing up the identified issues and challenges and discussing future perspectives of this novel material.

Oxygen‐modulated metal nitride clusters with moderate binding ability to insoluble Li2Sx for reversible polysulfide electrocatalysis

AbstractMultiphase sulfur redox reactions with advanced homogeneous and heterogeneous electrochemical processes in lithium–sulfur (Li–S) batteries possess sluggish kinetics. The slow kinetics leads to significant capacity decay during charge/discharge processes. Therefore, electrocatalysts with adequate sulfur‐redox properties are required to accelerate reversible polysulfide conversion in cathodes. In this study, we have fabricated an oxygen‐modulated metal nitride cluster (C‐MoNx‐O) that has a moderate binding ability to the insoluble Li2Sx for reversible polysulfide electrocatalysis. A Li–S battery equipped with C‐MoNx‐O electrocatalyst displayed a high discharge capacity of 875 mAh g−1 at 0.5 C. The capacity decay rate of each cycle was only 0.10% after 280 cycles, which is much lower than the control groups (C‐MoOx: 0.16%; C‐MoNx: 0.21%). Kinetic studies and theoretical calculations suggest that C‐MoNx‐O electrocatalyst presents a moderate binding ability to the insoluble Li2S2 and Li2S when compared to the C‐MoOx and C‐MoNx surfaces. Thus, the C‐MoNx‐O can effectively immobilize and reversibly catalyze the solid–solid conversion of Li2S2–Li2S during charge–discharge cycling, thus promoting reaction kinetics and eliminating the shuttle effect. This study to design oxygen‐doped metal nitrides provides innovative structures and reversible solid–solid conversions to overcome the sluggish redox chemistry of polysulfides.image

Atomistic global optimization X: A Python package for optimization of atomistic structures.

Modeling and understanding properties of materials from first principles require knowledge of the underlying atomistic structure. This entails knowing the individual chemical identity and position of all atoms involved. Obtaining such information for macro-molecules, nano-particles, and clusters and for the surface, interface, and bulk phases of amorphous and solid materials represents a difficult high-dimensional global optimization problem. The rise of machine learning techniques in materials science has, however, led to many compelling developments that may speed up structure searches. The complexity of such new methods has prompted a need for an efficient way of assembling them into global optimization algorithms that can be experimented with. In this paper, we introduce the Atomistic Global Optimization X (AGOX) framework and code as a customizable approach that enables efficient building and testing of global optimization algorithms. A modular way of expressing global optimization algorithms is described, and modern programming practices are used to enable that modularity in the freely available AGOX Python package. A number of examples of global optimization approaches are implemented and analyzed. This ranges from random search and basin-hopping to machine learning aided approaches with on-the-fly learnt surrogate energy landscapes. The methods are applied to problems ranging from supported clusters over surface reconstructions to large carbon clusters and metal-nitride clusters incorporated into graphene sheets.

Chemical Bonding in Transition Metal Nitride Os3N3 + Cluster: 6π Inorganic Benzene and δ2δ*1δ*1 Aromaticity.

Inorganic benzene-like clusters with a planar hexagonal ring are of interest in chemistry, as are new types of aromaticity, multifold aromaticity, and in particular δ aromaticity beyond carbon-based organic systems. Here we report on a computational study of chemical bonding in a binary Os3N3+D3h (7A2″) cluster. This transition metal nitride cluster assumes a perfectly planar, heteroatomic, hexagonal geometry. An array of quantum chemistry tools is exploited to elucidate the electronic, structural, and bonding properties of D3h Os3N3+ cluster, which include canonical molecular orbitals, adaptive natural density partitioning, natural bond orbital analysis, orbital composition calculations, and nucleus-independent chemical shifts. The computational data collectively support the bonding picture of 2-fold π/δ aromaticity: 6π electrons delocalized over all Os/N centers versus an Os-based 4δ framework in the unique δ2δ*1δ*1 configuration. The π sextet renders this heteroatomic cluster an inorganic analog of benzene. Transition metal-based inorganic benzenes are unknown in the literature, to our knowledge. The triplet 4δ electron-counting is a rare case of d-orbital aromaticity and δ-aromaticity, following the reversed 4n Hückel rule for aromaticity in a triplet system. This bonding picture is concrete, differing fundamentally from a recent study on the relevant system.

Structural interconnections and the role of heptagonal rings in endohedral trimetallic nitride template fullerenes.

Recent experiments indicate that fullerene isomers outside the classical definition can also encapsulate metallic atoms or clusters to form endohedral metallofullerenes. Our systematic study using DFT calculations, suggests that many heptagon-including nonclassical trimetallic nitride template fullerenes are similar in stability to their classical counterparts, and that conversion between low-energy nonclassical and classical parent cages via Endo-Kroto insertion/extrusion of C2 units and Stone-Wales isomerization may facilitate the formation of endohedral trimetallic nitride fullerenes. Close structural connections are found between favored isomers of trimetallic nitride template fullerenes from C78 to C82 . It appears that the lower symmetry and local deformations associated with introduction of a heptagonal ring favor encapsulation of intrinsically less symmetrical mixed metal nitride clusters. © 2016 Wiley Periodicals, Inc.

ChemInform Abstract: Lanthanides and Actinides: Annual Survey of Their Organometallic Chemistry Covering the Year 2013

AbstractReview: 187 refs.

Hydrogen adsorption of Be-, Zn-, and Cd-zeolitic imidazolate framework-23: A comparative study

Hydrogen adsorption energies of Be-, Zn-, and Cd-zeolitic imidazolate framework-23 were investigated using the Van der Waals density functional theory implemented in the Quantum ESPRESSO program. From the structural parameters of these systems, we found that the imidazole ligand is unchanged and only the tetrahedral metal nitride cluster is varied. Moreover, our results revealed that the Cd-zeolitic imidazolate framework-23 has the highest electric dipole moment followed by Zn- and Be-zeolitic imidazolate framework-23. On the basis of hydrogen adsorption energy calculations, we found that hydrogen molecules cannot bind with either Be- or Zn-zeolitic imidazolate framework-23 at any of the considered adsorption sites, whereas hydrogen molecules can be trapped on the Cd-zeolitic imidazolate framework-23 with the hydrogen binding energy in the range from 60 to 130 meV. This result suggested that replacing Zn in the metal nitride cluster with a larger metal can enhance the hydrogen adsorption energy of zeolitic imidazolate framework-23.

Large Ions in Mixed Metal Nitride Clusters: Gadolinium, Thulium, and Holmium

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New Isomers of Trifluoromethylated Derivatives of Metal Nitride Cluster Fullerene: Sc3N@C80(CF3)n (n=14 and 16)

Sc(3)N@C(80) (I(h)) was trifluoromethylated with CF(3)I at 400 °C affording a mixture of CF(3) derivatives. Two isomers of Sc(3)N@C(80)(CF(3))(14) and Sc(3)N@C(80)(CF(3))(16) were separated by HPLC and investigated by X-ray crystallography. Detailed comparison of the four isomers revealed a strong influence of the exohedral CF(3) addition pattern on the behavior of the Sc(3)N cluster inside the C(80) fullerene cage.

Spin-Flow Vibrational Spectroscopy of Molecules with Flexible Spin Density: Electrochemistry, ESR, Cluster and Spin Dynamics, and Bonding in TiSc2N@C80

The recently isolated TiSc(2)N@C(80) was used to study the spin state of a Ti(3+) ion in a mixed metal nitride cluster in a fullerene cage. The electronic state of the new clusterfullerene is characterized starting with the redox behavior of this structure. It differs markedly from that of homometallic nitride clusterfullerenes in giving reversible one-electron transfers even on the cathodic scale. Both oxidation and reduction of TiSc(2)N@C(80) occur at the endohedral cluster changing the valence state of Ti from Ti(II) in anion to Ti(IV) in cation. The unpaired electron in TiSc(2)N@C(80) is largely fixed at the Ti ion as shown by low temperature ESR measurements. Isotropic g-factor 1.9454 points to the significant spin-orbit coupling with an unquenched orbital momentum of the 3d electron localized on Ti. Measurements with the frozen solution also point to the strong anisotropy of the g-tensor. DFT computations show that the cluster can adopt several nearly isoenergetic configurations. DFT-based Born-Oppenheimer molecular dynamics (BOMD) simulations reveal that, unlike in Sc(3)N@C(80), the cluster dynamics in TiSc(2)N@C(80) cannot be described as a 3D rotation. The cluster rotates around the Ti-N axis, while the Ti atom oscillates in one position around the pentagon/hexagon edge. Evolution of the spin populations along the BOMD trajectory has shown that the spin distribution in the cluster is very flexible, and both an intracluster and cluster-cage spin flows take place. Fourier transformation of the time dependencies of the spin populations results in the spin-flow vibrational spectra, which reveal the major spin-flow channels. It is shown that the cluster-cage spin flow is selectively coupled to one vibrational mode, thus, pointing to the utility of the clusterfullerene for the molecular spin transport. Spin-flow vibrational spectroscopy is thus shown to be a useful method for characterization of the spin dynamics in radicals with flexible spin density distribution.

Yb@C2n (n = 40, 41, 42): New Fullerene Allotropes with Unexplored Electrochemical Properties

A series of(13)C-enriched monoytterbium endohedral metallofullerenes (EMFs)-Yb@C(2n) (n = 40, 41, 42)-was synthesized and isolated. Their cage structures were systematically determined for the first time using computational and experimental (13)C NMR studies. The results revealed that all isomers adopt cage structures conforming to the isolated pentagon rule. In detail, Yb@C(80) possesses the C(2v)(3) cage; Yb@C(82)(I, II, III) bear C(s)(6), C(2)(5), and C(2v)(9) cages, respectively; and Yb@C(84)(II, III, IV) have C(2)(13), C(1)(12), and C(2)(11) cage structures, respectively. This is the first report describing C(2)(13)-C(84) and C(1)(12)-C(84) cage structures. It is noteworthy that the cage structures found for mono-EMFs generally differ from either the corresponding empty fullerenes or the related EMFs encapsulating more than one metal atom, indicating that the metal atom inside the fullerene cage plays an important role in determining the EMF structure. On the basis of the fact that the structure of Yb@C(2)(13)-C(84) resembles that of Yb@C(2)(5)-C(82), a metal-templated growth process was proposed as a kinetic factor controlling EMF formation. Furthermore, previous electrochemical studies of divalent EMFs have failed to observe their oxidation potentials, which have raised the assumption that such species are large-bandgap molecules. This study revealed that all isomers of Yb@C(2n) (n = 40, 41, 42) display one or two reversible oxidation steps together with four reversible reduction processes in 1,2-dichlorobenzene, even at a low scan rate (20 mV/s), which enables estimation of their electrochemical bandgaps (DeltaE = (ox)E(1)-(red)E(1)). The results show a DeltaE value of 0.88-1.41 V for Yb@C(2n) (2n = 40, 41, 42), which is much larger than the values of trivalent mono-EMFs (DeltaE < 0.5 V), but generally smaller than those of metal nitride cluster EMFs (1.4 V < DeltaE < 2.1 V). Results further demonstrated that the DeltaE values correlate reasonably with their relative abundances.

The Role of the Selected Metal in Mixed Metal Nitride Clusters

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Mixed Metal Nitride Clusters in Fullerene Cages: From DySc2N@C76 to Lu2CeN@C80 - Invited

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Large mixed metal nitride clusters encapsulated in a small cage: the confinement of the C68-based clusterfullerenes

Three novel C68-based mixed metal nitride clusterfullerenes, which comprise of a small non-IPR C68 cage encapsulating large nitride clusters including DySc2N, LuSc2N, and Lu2ScN, have been synthesized and isolated, resulting in overpassing the confinement of the C68 cage.

The Role of an Asymmetric Nitride Cluster on a Fullerene Cage: The Non-IPR Endohedral DySc2N@C76

The first non-IPR C(76) cage based on a mixed metal nitride cluster, DySc(2)N@C(76), was successfully synthesized and isolated. DySc(2)N@C(76) is a stable fullerene with a small band gap of 0.96 eV. According to the FTIR spectroscopic study in combination with extensive DFT calculations, the cage structure of DySc(2)N@C(76) has been assigned to the non-IPR C(s): 17490-I isomer having two pairs of the adjacent pentagons. DySc(2)N@C(76)provides the first example of stabilization of the non-IPR C(76) cage by encapsulation of an asymmetric DySc(2)N mixed cluster, revealing the role of the cluster structure on the stability of the fullerene cage. As the asymmetric DySc(2)N cluster has a more suitable geometry for the inner space of the C(76) cage compared to that of the homogeneous clusters like Sc(3)N or Dy(3)N, the highest yield for C(76)-based cluster fullerenes with the Dy(x)Sc(3)-(x)N mixed nitride cluster is achieved for the DySc(2)N@C(76)

Resonant Ionization Using IR Light: A New Tool To Study the Spectroscopy and Dynamics of Gas-Phase Molecules and Clusters

Resonant IR excitation of gas-phase molecules and clusters can lead to superhot species that thermally emit an electron. Monitoring the mass selected ion yield as a function of IR laser frequency yields the IR-REMPI (infrared resonance enhanced multiphoton ionization) spectrum of the molecule or cluster. Although this IR-REMPI spectrum is not the same as the linear absorption spectrum, it can be quite similar and it yields valuable information on the IR optical properties of the species investigated. In this article, the method and the necessary tools are presented. Results from experiments on fullerenes, metal carbide, metal oxide, and metal nitride clusters are shown.

Dehydrogenation of ammonia by early transition metals: formation of metal nitride clusters

The dehydrogenation of NH 3 by Ti, Zr, and Nb cations, produced in a laser-induced plasma reactor, is found to form both neutral and cationic clusters. Depending on the conditions, either the production of neutral metal nitride clusters is favored or, the formation of cationic `precursor' metal nitride clusters containing additional intact NH 3 is observed. The neutral clusters are formed when full dehydrogenation of the NH 3 is achieved, while the cationic precursor species are formed under conditions where a large fraction of the NH 3 remains intact. Metastable dissociation studies show that intact NH 3 molecules are bound to the developing transition metal nitride clusters.

Time-resolved high-resolution electron microscopy of structural stability in mgo clusters

Structure and stability of atomic clusters have been studied by time-resolved high-resolution electron microscopy (TRHREM). Typical examples are observations of structural fluctuation in gold (Au) clusters supported on silicon oxide films, graphtized carbon films and magnesium oxide (MgO) films. All the observations have been performed on the clusters consisted of single metal element. Structural stability of ceramics clusters, such as metal-oxide, metal-nitride and metal-carbide clusters, has not been observed by TRHREM although the clusters show anomalous structural and functional properties concerning to solid state physics and materials science.In the present study, the behavior of ceramic, magnesium oxide (MgO) clusters is for the first time observed by TRHREM at 1/60 s time resolution and at atomic resolution down to 0.2 nm.MgO and gold were subsequently deposited on sodium chloride (001) substrates. The specimens, single crystalline MgO films on which Au particles were dispersed were separated in distilled water and observed by using a 200-kV high-resolution electron microscope (JEOL, JEM2010) equipped with a high sensitive TV camera and a video tape recorder system.