Ionization Potentials Of Clusters Research Articles

Density functional theory study on the beryllium clusters doped with silicon atom

An all-electron calculation on BenSi (n = 1–12) clusters has been performed by using density functional theory with the generalized gradient approximation at the PW91 level. The results reveal that the lowest energy geometries of BenSi (n = 1–12) clusters may be generated by substituting a Si atom for one Be atom of the Ben+1 clusters. In addition, Si atom tends to occupy external locations of main Ben clusters and bonds with multiple Be atoms in the BenSi (n > 2) clusters. The average binding energy of BenSi clusters is higher than that of pure Ben+1 clusters, indicating that the doped of the Si atom enhances the cluster's binding force. Compared with pure Ben+1 clusters, the HOMO-LUMO GAP of Be7Si, Be8Si, and Be10Si clusters increase while the HLG of other BenSi clusters(n = 1–3,5,9,11,12) decreas. The vertical ionization potential and vertical electron affinities curves of clusters have the same general trend. The VIP of the cluster decreases gradually while the VEA increases gradually. The doping of the Si atom greatly influences the stability of pure Ben clusters, and the analysis of energy and electronic properties of BenSi clusters reveals that the Be3Si cluster is the magic number structure in the system.

Ionization potentials of metal clusters studied with a broad range, tunable vacuum ultraviolet light source.

In this work, we present an alternative to complex laser setups or synchrotron light sources to accurately measure the ionization potentials of metal clusters. The setup is based on a commercial Xe flash lamp, combined with a vacuum monochromator, and has been applied to determine the ionization potentials of Snn clusters with n = 8-12 atoms. The uncertainty in the determination of the ionization potentials is mainly caused by the bandwidth of the monochromator. The adiabatic ionization potentials (AIPs) are extracted from experimental photoionization efficiency curves. Franck-Condon simulations are additionally used to interpret the shape and onset of the photo-ion yield. The obtained AIPs are (all energies are in eV) Sn8 (6.53 ± 0.05), Sn9 (6.69 ± 0.04), Sn10 (6.93 ± 0.03), Sn11 (6.34 ± 0.05), and Sn12 (IsoI 6.64 ± 0.04 and IsoIII 6.36 ± 0.05). Furthermore, the impact of multiple isomers present in the experiment on the photo-ion yield is addressed and compared with other experimental data in the literature.

NaxSy Nanokümelerinin Elektronik ve Yapısal Özellikleri

In this study, the structural and electronic properties of NaxSy (x+y=5) nanoclusters were investigated by density functional theory (DFT). Na-S is a material with potential in battery technologies. Therefore the smallest configurations of Na and S alloys are essential for applications in nanotechnology. Because electronic properties depend on the geometric structure, the minimum energy configurations were presented in detail. The most stable systems were determined as S5 and NaS4. The highest HLG value was obtained for the Na2S3 nanocluster. HLG values decrease with Na and S atom increase in bare clusters. Adding the S atoms to Na clusters or Na atoms to S clusters reduces the HLG values in general. Ionization potential and electron affinity values of clusters were also presented.

Molybdenum Oxide Clusters: Structure, Stability, and Electronic Properties.

Ab initio calculations were carried out to understand the structural, electronic, and energetic properties of molybdenum oxide clusters, MomOn (m = 1-6; n = 1-3m), to understand the relationships between size, composition, and reactivity. In clusters with a low oxygen-to-molybdenum ratio, there are bridge-bonded and linearly bonded oxygen atoms on a molybdenum core, while at higher ratios, Mo atoms are separated from each other and oxygen atoms located between the molybdenum atoms. The energy gap between the highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) widens with n, i.e., at a high oxygen-to-molybdenum ratio. Stoichiometric MomO3m clusters (m > 1) have a HOMO-LUMO gap that ranges from 2.6 to 3.4 eV in neutral conditions and less than 0.6 eV in ionic states. The ionization potential of MomO3m clusters is higher than 10 eV. MomOn clusters qualitatively and quantitatively exhibit a similar electronic structure to the bulk. The energy of the reduction reaction, MomOn → MomOn-1 + 1/2O2, is on average lower in clusters with high oxygen content; for example, the reduction energies of Mo6O18 and Mo6O9 are 2.23 and 5.19 eV, respectively. In the fragmentation of MomOn clusters, the general trend for clusters with a low oxygen-to-molybdenum ratio is the separation of a Mo atom or a Mo2 dimer from the cluster, while clusters with higher oxygen content mostly form stoichiometric MoO3, Mo2O6, and Mo3O9 clusters.

Theoretical study of the structures and electronic properties for NiX (X = Na–Cl) clusters

Using the first-principles calculations, we study the structural, electronic and magnetic properties of the neutral and ionic Nin-1X (n = 19–23; X = Na–Cl) clusters. The calculations are performed using the density functional theory with the PBE exchange–correlation energy functional. The results reveal that the most stable structures of Nin-1X (X = Na, Mg, Al, Si) clusters are all similar to those of corresponding Nin clusters, while there are substantial structural deformations of Nin-1X (X = P, S, Cl) clusters. From the optimized results, a systematic analysis is carried out to obtain the relative stability, charge transfer, magnetic moments, density of states, electron affinity and ionization potential of Nin-1X clusters. Our findings also suggest how to change the stability, electronic and magnetic properties by doping different atoms in Ni clusters.

Analysis of the ionization potentials of small superalkali lithium clusters based on quantum Monte Carlo simulations

In order to investigate the electronic correlation effects in the ionization potentials of small lithium clusters, we obtain accurate ground-state energies using the diffusion quantum Monte Carlo simulation. We decompose both the adiabatic and vertical ionization potentials of the clusters into physical components to analyze the nature of the superalkali characteristics of the lithium clusters. We find that the electron-correlation contribution to the ionization potential is mostly canceled out by the orbital relaxation with net contribution less than 0.5 eV. The superalkali characteristics of the clusters is basically determined by the electrostatic and exchange interactions.

Quantum-Size Dependence of the Energy for Vacancy Formation in Charged Small Metal Clusters. Drop Model

Self-consistent computations of the monovacancy formation energy are performed for Na N , Mg N , and Al N (12 < N ≤ 168) spherical clusters in the drop model for stable jelly. Scenarios of the Schottky vacancy formation and “bubble vacancy blowing” are considered. It is shown that the asymptotic behavior of the size dependences of the energy for the vacancy formation by these two mechanisms is different and the difference between the characteristics of a charged and neutral cluster is entirely determined by the difference between the ionization potentials of clusters and the energies of electron attachment to them.

Stability, structural and electronic properties of ternary Pd Au Ag clusters (x + y + z = 7): A theoretical study

Abstract Full range of Au and Ag doped Pd clusters, PdxAuyAgz with x + y + z = 7 in their ground states, are studied using the density functional theory (DFT) at TPSSTPSS method with SDD pseudopotential. The average interatomic distance, chemical order, charge distribution, binding energy, mixing energy, finite difference energy, vertical ionization potential, electron affinity and HOMO-LUMO gap of the ternary clusters are evaluated as a function of the whole concentration range, from which the mutual influences of Au and Ag dopants on the properties of Pd cluster are predicted and analyzed.

Energy Characteristics of Small Metal Clusters Containing Vacancies

Self-consistent calculations of spatial distributions of electrons, potentials, and energies of dissociation, cohesion, vacancy formation, and electron attachment, as well as the ionization potential of solid Al N , Na N clusters (N ≥ 254), and clusters containing a vacancy (N ≥ 12) have been performed using a model of stable jellium. The contribution of a monovacancy to the energy of the cluster, the size dependences of the characteristics, and their asymptotic forms have been considered. The calculations have been performed on the SKIT-3 cluster at the Glushkov Institute of Cybernetics, National Academy of Sciences of Ukraine (Rpeak = 7.4 Tflops).

Квантово-размерная зависимость энергии образования вакансии в заряженных малых металлических кластерах. Капельная модель

AbstractSelf-consistent computations of the monovacancy formation energy are performed for Na_ N , Mg_ N , and Al_ N (12 &lt; N ≤ 168) spherical clusters in the drop model for stable jelly. Scenarios of the Schottky vacancy formation and “bubble vacancy blowing” are considered. It is shown that the asymptotic behavior of the size dependences of the energy for the vacancy formation by these two mechanisms is different and the difference between the characteristics of a charged and neutral cluster is entirely determined by the difference between the ionization potentials of clusters and the energies of electron attachment to them.

On the calculation of the energies of dissociation, cohesion, vacancy formation, electron attachment, and the ionization potential of small metallic clusters containing a monovacancy

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 N , Li N (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).

Tuning the energetics and tailoring the optical properties of silver clusters confined in zeolites.

The integration of metal atoms and clusters in well-defined dielectric cavities is a powerful strategy to impart new properties to them that depend on the size and geometry of the confined space as well as on metal-host electrostatic interactions. Here, we unravel the dependence of the electronic properties of metal clusters on space confinement by studying the ionization potential of silver clusters embedded in four different zeolite environments over a range of silver concentrations. Extensive characterization reveals a strong influence of silver loading and host environment on the cluster ionization potential, which is also correlated to the cluster's optical and structural properties. Through fine-tuning of the zeolite host environment, we demonstrate photoluminescence quantum yields approaching unity. This work extends our understanding of structure-property relationships of small metal clusters and applies this understanding to develop highly photoluminescent materials with potential applications in optoelectronics andbioimaging.

First principles study on the size evolution and stability of (AgF)n (n = 1–12) clusters

The structural evolution of (AgF)n (n=1–12) clusters has been studied by first principles global minimization technique, namely, a genetic algorithm from density functional theory geometry optimization (GA-DFT). The growth sequence and pattern for n from 1 to 12 are analyzed from the perspective of geometric structures. The average binding energy per cluster, vertical and adiabatic ionization potentials, NICS-scan curves (partial clusters) are examined. The global minimum structures are planar single-ring conformations at n=1–5, and tubular conformations when n=6, 9 and 12, where they contain triangular units. When n=7 and 11, the clusters present butterfly and helix conformations, respectively. When n=8 and 10, the clusters are separate-ring structures. One more stable structure has been found for (AgF)6 cluster in comparison with previous work, indicating the power of DFT-based genetic algorithm in finding new structures for clusters. Several magic sizes of higher stability and symmetry are discovered. In particular, we find that when n=3, 6, 9 and 12, the clusters are tubular structures with high stability and high aromaticity.

Quantum chemical studies on the structural and electronic properties of nickel sulphide and iron sulphide nanoclusters

Nanoclusters of nickel sulphide (NiS) n and iron sulphide (FeS) n for n = 3–5 are studied using B3LYP exchange correlation function with 6-31G as a basis set. The structural stability of different isomers of NiS and FeS is analysed with the optimized energy, binding energy and vibrational studies. The electronic properties of isomers are discussed in terms of HOMO–LUMO gap, ionization potential, electron affinity, and embedding energy of different clusters. Based on the calculated energy, planar ring, linear ladder and bipyramidal cube of NiS and FeS nanoclusters are found to be more stable. The increase in number of atoms in the clusters leads to increase in its stability. The dipole moment is high for planar rhombus and linear ladder structures of NiS and FeS nanoclusters. The ionization potential and electron affinity are high for planar ring structure of NiS and FeS clusters. The value of energy gap of linear ladder NiS nanocluster and cube and bipyramidal cube structures of FeS is found to be low. The binding energy for cube structure of NiS and FeS clusters is found to be high. Hexagonal ring structure of NiS and FeS clusters has low embedding energy value. The other parameters such as dipole moment and point symmetry are also discussed. The structural stability and electronic properties will provide an insight for experimentalist to tailor new materials that have potential importance in engineering applications.

DFT studies on the stability of linear, ring, and 3D structures in CdTe nanoclusters

In DFT studies with the B3LYP/LanL2DZ basis set the different structures, linear, ring, and 3D, of cadmium telluride (CdTe) n clusters for n = 2–7 were completely optimized. The stability, dipole moment, and point groups of the different clusters were studied. The HOMO–LUMO energy gap, ionization potential, electron affinity, relative stability, and binding energy of different clusters were studied and compared with values for different isomers. These results for the different properties of CdTe nanoclusters will give clear information enabling the design of new materials with potential importance in thin-film solar cells.

Accurate ionization potential of gold anionic clusters from density functional theory and many-body perturbation theory

We present a theoretical study of the ionization potential in small anionic gold clusters, using density functional theory, with and without exact-exchange, and many body perturbation theory, namely the G0W0 approach. We find that G0W0 is the best approach and correctly describes the first ionization potential with an accuracy of about 0.1 eV.

Size evolution of electronic properties in free antimony nanoclusters

The evolution of electronic properties in free antimony (Sb) nanoclusters as a function of the cluster size has been studied experimentally using synchrotron radiation. Antimony 4d core-level and valence-band regions have been probed, and the 4d binding energies and valence ionization potentials of clusters of various mean sizes have been determined. The binding-energy shifts with respect to polycrystalline solid have been used for deriving the electronic properties of the clusters. The observed results suggest that even large Sb clusters are not metallic.

Quantum Chemical Studies on NiO Nanoclusters

The structural stability of nickel oxide (NiO)n (n=1�7) nanoclusters were studied using Gaussian 03W program package with B3LYP/6-31G level basis set. It is observed that the ring structure is more stable in most cases compared to other struc- tures(Linear and 3D). For n>6 the 3D structure is no longer stable. From the optimiza- tion results of (NiO)n clusters it is found that when the atoms in the cluster increases it leads to the increase in the stability. The dipole moment of each cluster is also stud- ied which shows that the dipole moment depends upon the arrangement of atoms in the cluster. The HOMO LUMO gap, ionization potential, electron affinity and binding energies of Nickel Oxide clusters have been calculated and reported.

Ab initio determination of the ionization potentials of water clusters (H2O)n (n = 2−6)

High-level quantum-chemical ab initio coupled-cluster and multiconfigurational perturbation methods have been used to compute the vertical and adiabatic ionization potentials of several water clusters: dimer, trimer, tetramer, pentamer, hexamer book, hexamer ring, hexamer cage, and hexamer prism. The present results establish reference values at a level not reported before for these systems, calibrating different computational strategies and helping to discard less reliable theoretical and experimental data. The systematic study with the increasing size of the water cluster allows obtaining some clues on the structure and reductive properties of liquid water.

Ionization potential and ion yield of CsM clusters sputtered from Si

We calculated the ionization potentials for 34 CsM molecules (where M is the element of the periodic table) by using SIESTA code, on the basis of the density functional theory. The calculated ionization potentials of CsM molecules were found essentially less than the ionization potentials of related atoms. Experimental SIMS relative sensitivity factors were found for the CsM+ cluster ions by using implanted standards. Exponential dependence between the relative sensitivity factors of CsM+ cluster ions and their ionization potentials was obtained. This lets us suggest that there is a direct emission of the CsM molecules during the cesium ion beam sputtering process; ionization of the CsM molecules occurs at the emitted surface because of the same mechanism as for sputtered atoms. Copyright © 2012 John Wiley &amp; Sons, Ltd.