Nanoalloy Clusters Research Articles

Microwave‐assisted control of PtNi nanoalloy clusters on the nitrogen‐doped graphene oxide for energy conversion with oxygen reduction reaction and hydrogen evolution reaction

AbstractResearch on the production and utilization of hydrogen energy is essential to overcome the environmental issues caused by fossil fuels. Herein, we anchor PtNi nanoalloy clusters (Pt‐Ni NACs) on nitrogen‐doped graphene oxide (NrGO) by a facile microwave‐assisted synthesis and analyze the variations of catalyst properties based on the PtNi composition and the presence of nitrogen. Ni inclusion in the Pt matrix can induce lattice strain and change the electronic structure, while the doped nitrogen into the graphene can enhance electron transfer and improve the durability of the catalyst through strong chemical bonding with the alloy clusters. TEM analysis discovers that the NACs are uniformly decorated in a few‐nanometer‐size on the graphene surface, and the formation of the PtNi NACs and structural changes according to composition are confirmed through XRD and XPS. In addition, the structural changes due to N‐doping and its bonding with the NACs are observed through Raman spectroscopy and XPS. Electrochemical measurements reveal that Pt2.6Ni NACs/NrGO exhibits the highest ORR onset potential (0.893 V) and the lowest HER overpotential at 10 mA cm−2 (22 mV) among other catalysts, and those activities are almost unchanged under long‐term durability tests. From these results, Pt2.6Ni NACs/NrGO is utilized in a zinc‐air battery (ZAB) system, demonstrating better battery performance than commercial Pt and Ir‐based catalysts. Moreover, it is applied to hydrogen collection, showing linear trend in hydrogen production over time, confirming the catalyst's availability in hydrogen production and utilization.image

Improving electronegativity of N-doped carbon by encapsulating CoFe alloy clusters with a chainmail-like structure for high-energy sodium-ion capacitors

Metal-nitrogen-carbon has attracted great research interests for sodium storage. However, the limited and unstable M-Nx active sites result in poor rate performance and inferior cycle life. Herein, CoFe nanoalloy clusters...

Theoretical study on structural evolution, photoelectron and vibrational spectra, and thermochemistry properties of neutral, anionic and di-anionic titanium-doped tin (TiSnn0/−/2− (n = 4–17)) nanoalloy clusters

The structural evolution, chemical stability, electronic and vibrational properties, as well as charge transfer and bonding character of TiSnn0/−/2− (n = 4–17) clusters have been performed with density functional theory calculations using ABCluster search technique. Structurally, it is found that the growth patterns prefer three kinds of absorbed stages from polygonal bipyramidal configuration for n = 4–6, to absorbing additional Sn on the adjacent surfaces of pentagonal bipyramid unit from n = 7–12, and finally to the TiSn130/−/2− cluster as the first foundational architectures, of which the encapsulated cage structure is formed when n = 11. The simulated PES spectra agree with available experiments. More interestingly, the neutral TiSn16 cluster not only possesses the high thermodynamic and relative stability but also preferable photochemical reactivity, that can be further explained by superatom features and delocalized multi-center bonds (AdNDP), while the strong p-d hybridization between Ti atom and Sn unit plays an important role in the stabilities of clusters, making it as the most suitable building units. In addition, the UV–Vis absorption spectra of TiSn16 are discussed, and the main transitions of crucial excited states are analyzed in detail. The Infrared and Raman vibrational characteristic peaks of all these neutral and charged species are properly assigned, of which the TiSnn0/−/2− (n = 10–17) clusters possess degenerating deformation mode of Ti atom wagging in Sn cage framework (Infrared active) and breathing mode of Sn cage framework (Raman active). All these findings will provide a further understanding for the nanoalloy cluster as the most suitable building block with further development as a potential optoelectronic material.

Atomic-scale insights into the precipitation behaviors of copper atoms in liquid lithium

The precipitation of corrosion products in liquid lithium (Li) is one of the concerns in the compatibility of liquid Li with solid materials. In this work, molecular dynamics simulations are employed to investigate the precipitation behavior of copper (Cu) atoms in liquid Li at different temperatures. It is found that Cu atoms combine with Li atoms to form CuLix nanoalloy clusters during the precipitation process. The cluster analysis revealed that the low temperature environment not only facilitates the formation of large clusters but also promotes their transformation from amorphous structure to ordered Cu-Li solid solution. The phase transition occurs because the merger and growth of clusters reduces the potential energy of the internal atoms. In addition, the CuLix nanoalloy clusters bind the Li atoms through internal alloying and surface adsorption, which in turn increases the viscosity of liquid Li. The larger the cluster size, the greater the viscosity increment.

Understanding the Stability of an Unprecedented Si-Be Bond within Quantum Confinement.

As of today, the Si-Be bond remains underexplored in the literature, and therefore its anomalous behavior continues to be an unsolved puzzle to date. Therefore, the present study aims at evaluating the integrity of an unprecedented Si-Be bond within quantum confinement. To accomplish this, first-principles-based calculation are performed on Be-doped silicon clusters with atomic sizes 6, 7, and 10. Silicon clusters are sequentially doped with one, two, and three Be atoms, and their thermal response is registered in the temperature range of 200-1500 K, which discloses several research findings. During the course of the simulations, the clusters face various thermal events such as solid cluster phase, rapid structural metamorphosis, and fragmentation. Si-Be nanoalloy clusters are noted to be thermally stable at lower temperatures (200-700 K); however, they begins to disintegrate earlier at a temperature as low as 800 K. This lower stability is attributed to the weak nature of Si and Be heteroatomic interactions, which is corroborated from the structural and electronic property analysis of the doped clusters. In addition to this, the performance of Be-doped clusters at finite temperatures is also compared with the thermal response of two other popular systems, viz., C- and B-doped silicon clusters.

Joint electric and magnetic beam deflection experiments and quantum chemical studies of MSn12 clusters (M = Al, Ga, In): on the interplay of geometric structure and magnetic properties in nanoalloys.

MSn12 clusters (M = Al, Ga, In) were studied in electric and magnetic beam deflection experiments at temperatures of 16 K and 30 K. For all three species, the results of the electric beam deflection experiments indicate the presence of two structural isomers of which one is considerably polar. The magnetic beam deflection experiments show atom-like beam splitting (superatomic behavior) with g-factors of 2.6-2.7 for a fraction of the clusters in the molecular beam, indicating significant spin-orbit coupling. On the one hand, we investigate by several experiments combining electric and magnetic deflectors how the superatomic and polar fractions are linked proving the correlation of the Stark and Zeeman effects. On the other hand, the magnetic deflection behavior is examined more thoroughly by performing quantum chemical calculations. By systematic distortion of an artificial icosahedral tin cage towards the global minimum structure, which has a pyritohedral geometry, the shifts in the magnitude of the g-factor are found to be mainly caused by a single dominant electronic excitation. This allows one to develop a semi-quantitative understanding of the magnetic behavior. On the basis of avoided crossings in the rotational Zeeman diagram, simulations of the magnetic beam deflection comprising computed rotational constants, vibrational modes, g-factors and spin-rotation coupling constants are performed which resemble our experimental findings in satisfactory agreement. With this, a better understanding of the magnetic properties of nanoalloy clusters can be achieved. However, the geometric structures of the polar isomers are still unknown.

Quantum computational study of small bismuth–cobalt nanoalloy clusters

Quantum computational study of small bismuth–cobalt nanoalloy clusters

Structural, mixing, electronic and magnetic properties of small Cu-Pd nanoalloy clusters

Bimetallic CumPdn nanoalloy clusters of small size (m+n ≤ 12) are systematically studied using the spin polarized density functional theory to understand the evolution of structural, mixing, electronic and magnetic properties with size and composition of the binary system. The lowest-energy configurations of the series of bimetallic clusters are determined from unbiased global search with genetic algorithm. With the increase of size, Cu-Pd clusters tend to adopt compact geometries. For a given cluster size, Pd atom prefers the outer position, while Cu atom favors the inner site. Stability analysis reveals that nanoalloy formation for CumPdn clusters is favored for the overall range of sizes and compositions. The small changes in structures of magic clusters with their neighboring compositions indicate that their high stability is primarily due to the variation in composition, not to the change in structure. The electronic state of the Pd atom is promoted upon the formation of the Cu-Pd nanoalloy clusters, while that of the Cu atom remains almost unchanged. The magnetic moments of CumPdn clusters exhibit an evident oscillation behavior with the composition, which can be attributed to the substantial hybridization between the electronic states of Pd and Cu.

A systematic investigation of structural growth patterns and electronic properties of [LuGen]+/0 and [Gen+1]+/0 (n = 1–17) nanoalloy clusters

The geometries, stabilities, evolutions, and electronic properties of lutetium-doped germanium nanoalloy clusters LuGen (n = 1–17) in the neutral and cationic state are studied and compared with Gen+1 clusters by using unbiased global search method combined with a hybrid density functional approach. The results reveal that neutral and cationic structural growth patterns prefer Lu-substituted Gen+1 for n = 1–8, Lu-linked configuration for n = 9–14 (for cation n = 9–15) in which Lu atom links two Ge subclusters, and Lu-encapsulated Ge cage-like motif for n = 15–17 (for cation n = 16–17). A binding energy analysis reveals that Lu-encapsulated motifs enhance the nanocluster stability. Lu-doped neutral and cationic germanium clusters can decrease their ionization potential. Natural population analysis shows that Lu in Lu-substituted and Lu-linked configurations acts as electron donor, but acts as electron acceptor in Lu-encapsulated structures. HOMO-LUMO energy gap analysis discloses that Lu-doped Ge clusters can lessen their chemical stability excluding LuGe12 and LuGe17. Thorough analysis of stability, chemical bonding, density of states, iso-chemical shielding surface and UV-Vis spectra revealed that [LuGe17]+ is magic nanoalloy cluster, and has an ideal chemical and thermal stability, making it the most preferable building block for optoelectronic materials. Additionally, Infrared and Raman spectra of [LuGe17]+ are also reported. The accordance between theoretical and experimental values for binding energies of Ge2–8 and ionization potentials of Ge2–16,18 clusters suggest that the calculations and analysis of results in this study are successful.

A Review on Nanoalloy Clusters: Theory to Applications

Nanoalloy clusters have attracted a lot of attention in recent times and have grown enormously in various domains, ranging from semiconductor, material sciences, biophysics, life sciences to earth sciences. In this report, we presented a review of nanoalloy clusters and their application. The background of clusters, nanoalloys and their isomers, their classification, and potential applications ranging from catalysis, optoelectronics, magnetic to bio-diagnosis are reported. Experimental techniques as well as the importance of theoretical and computational studies in nanoalloy clusters are also presented.

Structure and electronic properties of [AunV]λ (n = 1–9; λ = 0, ± 1) nanoalloy clusters within density functional theory framework

Structure and electronic properties of [AunV]λ (n = 1–9; λ = 0, ± 1) nanoalloy clusters within density functional theory framework

H2 Generation by Water Dissociation on Nano Alloy Clusters

H2 Generation by Water Dissociation on Nano Alloy Clusters

Computational analysis of [AunSi]+ (n = 1–5) nanoalloy clusters

Study of silicon doped gold nanoalloy cluster is of great importance due to its prospective applications in optoelectronic and photovoltaic cells. In this article, computational investigation of cationic state for silicon doped gold nanoalloy cluster [Au n Si] + (n = 1–5) is carried out with the help of Density Functional Theory (DFT) methodology. For optimization and modeling of clusters functional B3PW91/LANL2DZ is selected. Density functional theory based global descriptors along with dipole moment and symmetry configuration of [Au n Si] + are computed. The computed data illustrates that energy difference between HOMO and LUMO energy gap varies from 2.149 to 3.549 eV. Maximum stability is found for cluster [Au 3 Si] + with symmetry configuration D 3h whereas cluster [Au 4 Si] + with symmetry group C 2V shows the least stability. The HOMO-LUMO energy gap of [Au n Si] + nanoalloy clusters exhibits direct correlation with molecular hardness. An odd–even swinging behavior is noted among energy gap and number of gold atoms, indicating that cluster with odd number of gold atoms shows HOMO-LUMO gap higher in comparison with their contiguous system with even number of gold atoms.

Comparative research of configuration, stability and electronic properties of cationic and neutral [AuGen]λ and [Gen+1]λ (n=1-13, λ=0, +1) nanoalloy clusters

The configuration, stability, evolution, and electronic properties of neutral and cationic [AuGen]λ and [Gen+1]λ (n=1−13, λ=0, +1) nanoalloy clusters have been systematically investigated by using unbiased global search technique married with double-density functional strategy. The results reveal that although the neutral and cationic global minimal structures of gold-doped germanium clusters differ from each other when n=4, and 6–13, the evolution patterns are consistent. Attaching structures have been changed to Au-encapsulated motif at the turning point of n=11. The analyses of electronic structure and binding energy indicate that doping of an Au atom may decrease the stability of neutral Ge nanoclusters, but can enhance the stability of cationic Ge nanoclusters. The analyses of electronic property show that ionization potentials (IP) of Gen+1 cluster are larger than those of AuGen nanoalloy clusters, indicating that doping of an Au atom can decrease the ionization potential of neutral Ge nanoclusters. The analyses of HOMO and LUMO energy reveal that HOMO-LUMO gaps of neutral AuGen (n=1−13) with the exception of n=2 and 3 are smaller than that of Gen+1 clusters. For cations, the HOMO-LUMO gaps of [AuGen]+ are wider than that of [Gen+1]+ cluster when n=2, 5–7, and 9–11, narrower when n=3, 4, 8 and 13, and nearly identical when n=1 and 12. The PBE-DFT based global descriptors viz. Electronegativity, Hardness, Softness and Electrophilicity Index of [Gen+1]λ and [AuGen]λ (λ=0, +1; n=1−13) nanoclusters are estimated by means of HOMO-LUMO gap. And they possess highly correlation with HOMO-LUMO gap. The agreement between theoretical and experimental results such as IP, binding energy, HOMO-LUMO gap, and bond distance demonstrate the success of the computational analyses in this work.

Local coordination numbers of up to 19 in gadolinium-tin alloy nanoclusters.

A combined approach based on quantum-chemical calculations and molecular beam experiments demonstrates that in isolated nanoalloy clusters of type GdSnN, a total number of N = 19 tin atoms can be arranged around a central gadolinium atom. While the formation of the first coordination shell is incomplete for clusters with less than 15 tin atoms, the second coordination sphere starts to form for cluster sizes of more than 20 tin atoms. The magnetic properties of the clusters reveal that the tin atoms not only provide a hollow cage for Gd but also are chemically bound to the central atom. The calculated spin densities imply that an electron transfer from Gd to the tin cage takes place, which is similar to what is observed for endohedral metallofullerenes. However, the measured electric dipole moments indicate that in contrast to metallofullerenes, the Gd atom is located close to the center of the tin cage.

Structure and optical properties of (CuAg)n (n = 1–6) nanoalloy clusters within density functional theory framework

We have studied the structure and optical properties of bimetallic (CuAg)n (n = 1–6) nanoalloy clusters by using density functional theory (DFT) method. The computed data shows that HOMO-LUMO energy gaps of the clusters are in the range of 1.444–3.066 eV. The most stable cluster (CuAg)3 with symmetry group C1 and singlet spin multiplicity has an energy gap 3.066 eV, whereas the cluster (CuAg)6 with symmetry group C2 and singlet spin multiplicity shows the least energy gap (1.444 eV). Our study reveals an interesting correlation between energy gap, optical electronegativity, and refractive index. Computed data exhibits that clusters, in which Ag atoms are placed on the edge position and have less number of Ag–Ag bonds, display a large frequency range and the maximum intensity of IR and Raman spectra.

Theoretical Analysis of Au-Pd Nanoalloy Clusters: A DFT Study

The study of bimetallic nanoalloy clusters has attracted a lot of attention now a days due to its unique physico-chemical properties. Among several bimetallic clusters, the compound formed between gold and palladium is of high importance due to its interesting catalytic properties. Density Functional Theory (DFT) is highly dominating method to compute the electronic properties of materials. In this article, we have reported the physical and chemical properties of AunPd (n=1-6) nanoalloy clusters in terms of Conceptual Density Functional Theory (CDFT) based descriptors. The CDFT based descriptors viz. HOMO-LUMO energy gap, hardness, softness, electronegativity andelectrophilicity index of AunPd nanoalloy clusters have been calculated. The result exhibits that energy gap of Au-Pd clusters maintain linear relationship with hardness values and inverse relationship with softness values. The HOMO-LUMO energy gap also display odd-even oscillation behavior, in which cluster containing total number of even atoms are more stable as compared to their neighbor cluster with total number of odd atoms.

Structure and electronic properties of AunPt (n = 1–8) nanoalloy clusters: the density functional theory study

The study of bimetallic nanoalloy clusters is of considerable interest due to its interesting electronic, optical, magnetic and catalytic properties. The geometrical structure and electronic properties of AunPt (n = 1–8) nanoalloy clusters are studied by using the density functional theory methodology. The result exhibits that the ground-state configurations of AunPt clusters favour planar confirmation in this molecular range. The most stable cluster is Au3Pt, which is having rhombus structure with symmetry group C2v and can be considered as building blocks for developing large clusters. The computed HOMO-LUMO energy gap of Au3Pt nanoalloy cluster is 1.741 eV. The energy gap in this particular range supports the use of bimetallic clusters as nonlinear optical devices and optoelectronic materials. The DFT-based global descriptors viz. HOMO-LUMO energy gap, electronegativity, hardness, softness and electrophilicity index are also studied. The computed HOMO-LUMO energy gap and chemical hardness exhibit a pronounced odd-even oscillation behaviour as a function of cluster size, n.

Binary Nanoalloy Clusters: A Case Study for FeCr Clusters.

A study of FexCry binary nanoalloy clusters is carried out for sizes n=x+y=13 and 55, the first two closed shell structures. While for n=13, various compositions like x=12 and y=1; x=11 and y=2; x=10 and y=3 ; x=1 and y=12 are studied, for the larger size (n=55) the morphology of a Fe-rich cluster (Fe42Cr13) and a Cr-rich cluster (Fe13Cr42) are analysed. The potential energy surface of the nanoalloys are scanned thoroughly using an evolutionary genetic algorithm in conjunction with a density functional theory based first principles method and the most stable clusters are picked up for every size and composition. A definite hierarchy in Cr-Cr,Fe-Cr and Fe-Fe bonding strengths is seen to determine the stability of the clusters. Cr-Cr bonding is promoted over Fe-Cr bonding which in turn is preferred over Fe-Fe bonding in the nanoalloy systems.

A comparative study of structure, stabilities and electronic properties of neutral and cationic [AuSin]λ and [Sin+1]λ (λ = 0, +1; n = 1–12) nanoalloy clusters

Structure, stabilities and electronic properties of [AuSin]λ and [Sin+1]λ (λ = 0, +1; n=1-12) nanoalloy clusters are studied invoking Density Functional Theory methodology. To understand the chemical stability of the lowest energy structure of cluster, chemical parameters like, Binding Energy, Fragmentation Energy, Second Order Difference in Energy and HOMO-LUMO energy gap are studied with the variation of cluster size. The binding energy of neutral and cationic Sin+1 and AuSin clusters is gradually increasing along with the cluster size n. The second order difference in energy for pure Sin+1 and doped cluster AuSin shows an interesting odd-even alternation behavior. It is found that Si7, AuSi5, [Si5]+ and [AuSi7]+ are the most stable clusters. The HOMO-LUMO energy gap of neutral and cationic AuSin cluster is high as compare to their corresponding neutral and cationic Sin+1 cluster. It indicates that doping of Au atom enhances the energy gap of silicon clusters. The computed HOMO-LUMO gap of neutral and cationic AuSin clusters are in the range of 1.35–2.94 eV, which is suitable for microelectronics, optoelectronic devices and photovoltaics applications. Density Functional Theory based descriptors viz. Electronegativity, Hardness, Softness and Electrophilicity Index are also reported. The HOMO-LUMO energy gap of pure Si and doped cluster AuSin displays odd-even oscillation behavior as a function of cluster size, n. The close agreement between theoretical and experimental results supports and validates our computational analysis.