Stability Of Neutral Clusters Research Articles

How does the Geocosmos Control the Viruses in Biosphere: DNA, Ionospheric Microwaves and Water

The goal of the paper was to show that the phenomena observed in the works of L. Montagnier, the Nobel laureate on physiology, 2008, with the behavior of some bacteria and viruses (including the Human Imunodeficiency Virus), may be related to the effect of microwave fluxes primarily of ionospheric origin, to formation of water-containing complexes. A well-known mechanism of associative formation is taken into account, taking into account the high affinity for the proton in water molecules. The approach developed in our recent papers is used within the framework of supramolecular physics of complex molecular structures. Supramolecular physics describes a processes developing outside the molecules (atomic-molecular cores) in whose evolution to the complex forms (clusters, associates) electromagnetic radiation of external origin absorbed by exited Rydberg components of molecular complex takes part. Due to increasing value of orbital momentum of Rydberg electrons the stability of the complex grows because probability for forming a stable neutral cluster becomes higher as the electron more seldom penetrates into the ion core. We use the analogy with well known supramolecular chemistry proposed by J.-M. Lehn, the Nobel laureate on chemistry, 1987. He also discussed a possibility of contribution of cosmic influence both to information exchange in living organism and reaction to the environmental stimuli.

Role of 3d transition metal doping in determining the electronic structure and properties of small magnesium clusters: a DFT-based comparison of neutral and cationic states

We have carried out density functional theory calculation to study the evolution of geometric, energetic and electronic properties of Mgn (n = 2–10) clusters. The dispersion corrected ωB97X-D functional is found to be more efficient over the B3LYP + D3 method in determination of accurate structure and energetics of the gas phase small Mgn clusters. We have found that Mg4 possesses the smallest possible three-dimensional geometry and is the most stable cluster among the Mgn clusters studied here. We have therefore selected Mg4 cluster as a host for the doping of 3d transition metal (TM) atom to study the structural, electronic and magnetic properties of these TMMg30,+ clusters. MnMg3 and NiMg3+ clusters are found to be the most stable neutral and cationic TMMg3 clusters, respectively. The NBO and DOS analyses have shown that the stability of the TMMg30,+ clusters is governed by the charge transfer processes as well as the nature of interaction of the atomic orbitals. These studies also confirm that the neutral doped clusters exhibit covalent-like bonding while ionic type bonding is present in cationic clusters. Larger charge gains by the charge deficient TM cations from the Mg atoms in TMMg3+ make them relatively stable over the neutral clusters. The DOS and molecular orbital analyses reveal that the 3d orbitals of the dopant TM atoms actively participate in electronic charge transfer processes by maintaining their individuality in TMMg3 clusters, whereas they remain silent in this regard in case of TMMg3+ clusters. In both these cases, the TM0,+(3d) orbitals play the crucial role of tuning the magnetic moment. Therefore, the overall electronic structure and properties of TMMg30,+ clusters depend solely on the TM(3d) orbitals, which is governed by the charge transfer processes characterized by the charge state of the cluster. Graphical abstract

Density Functional Study on Structure and Bonding Nature of CO Adsorbed Rh n +/− (n = 2–8) Clusters

Systematic investigations on lowest energy CO adsorbed neutral and ionic Rhn (n = 2–8) clusters in the gas phase are performed with all electron relativistic method using density functional theory within the generalized gradient approximation. Geometrical and electronic parameters are evaluated to understand the bonding nature as well as the binding interaction of CO on stable neutral and ionic rhodium clusters. Anionic adducts exhibit higher adsorption energy along with smaller Rh–C and larger C–O bond distances in comparison to neutral and cationic RhnCO (n = 2–8) clusters. Synergic bond formation is noticed between rhodium and carbon atom of CO molecule due to back-donation of electron from metal d-orbitals to π* orbital of CO in the case of anionic and some neutral clusters. Angular and Mulliken charge analysis along with electron density distribution suggest that anionic rhodium clusters form strong bond with carbon atom of CO than the neutral and cationic clusters.

The chemical space of PbN-nBin and (PbN-nBin)+: A systematic study for N = 3-13.

A systematic exploration of the energy hypersurfaces of three to 13-atomic neutral and cationic binary lead-bismuth clusters is presented. Global minima for all 99 compositions (N = 3-13, n = 0-N) were obtained by a density functional theory based genetic algorithm, which was applied to every single composition, both for the neutral clusters and for the cations. Within the genetic algorithm, the energetically most favorable assignment of atom types to atom positions was found via aimed swapping of element types, based on first-order perturbation theory in the nuclear charge. Results of the genetic algorithm procedure were refined with high-level density functional treatments including also the effects of spin-orbit coupling. The resulting global minima were analyzed applying various stability criteria, finally yielding the ∼20 overall most stable neutral and cationic clusters in the chemical space of three to 13-atomic mixed lead bismuth clusters. In most cases, they are polyhedrons that obey the Wade-Mingos rules.

Density-Functional Study of Structural and Electronic Properties of the ZrnAl±m Clusters

<p>The geometries, stabilities, and electronic properties of Zr<em><sub>n</sub></em>Al<sup>±<em>m</em></sup> (<em>n</em> = 1 – 7 and <em>m</em> = 0, 1) clusters were investigated at the UB3LYP/LANL2DZ level. The variations of structural and electronic properties with the changes of <em>n</em> and <em>m</em> were probed. Several possible multiplicities of each cluster were tested. The multiplicity of the most stable neutral clusters is 4 instead of 2. For all the three differently charged of Zr<em><sub>n</sub></em>Al clusters, the lowest-energy geometry is in favor of three-dimensional structure when <em>n</em> ≥ 3. The Zr<sub>3</sub>Al<sup>+</sup>, Zr<sub>4</sub>Al<sup>–</sup>, Zr<sub>5</sub>Al<sup> +</sup>, Zr<sub>6</sub>Al<sup>– </sup>and Zr<sub>7</sub>Alclusters are more stable than their corresponding differently charged species of the same size. Moreover, the odd-even oscillations are found in the fragmentation energy and the second-order difference of total energies for Zr<em><sub>n</sub></em>Al<sup>– </sup>clusters. The Zr<sub>2</sub>Al<sup>+ </sup>cluster is more inert to chemical reaction than others judged by the HOMO-LUMO gaps. NBO analysis was done to analysis the electronic properties.</p>

Size and Charge Distributions of Stable Clusters Formed in Ion Sputtering of Metals

A theory of ion sputtering of metals in the form of neutral and charged clusters with their subsequent fragmentation into the stable state is developed. The theory is based on simple physical assumptions and is in good agreement with experiment. Results are presented in the form of formulas convenient for practical application. As an example, calculations of the total yield of stable neutral and charged clusters of silver, indium, and niobium are carried out.

Emission of charged and stable clusters during the ion sputtering of metal

A theory of the ion sputtering of metal in the form of excited neutral and charged clusters with their subsequent fragmentation to the stable state is developed. This theory is based on simple physical assumptions and agrees well with experiments. The results are presented in the form of practical formulas. The overall yields of stable neutral and charged clusters of silver, indium, and niobium are calculated as an example.

Electrical charging changes the composition of sulfuric acid–ammonia/dimethylamine clusters

Abstract. Sulfuric acid clusters stabilized by base molecules are likely to have a significant role in atmospheric new-particle formation. Recent advances in mass spectrometry techniques have permitted the detection of electrically charged clusters. However, direct measurement of electrically neutral clusters is not possible. Mass spectrometry instruments can be combined with a charger, but the possible effect of charging on the composition of neutral clusters must be addressed in order to interpret and understand the measured data. In the present work we have used formation free energies from quantum chemical methods to calculate the evaporation rates of electrically charged (both positive and negative) sulfuric acid–ammonia/dimethylamine clusters. To understand how charging will affect the composition of electrically neutral clusters, we have compared the evaporation rates of the most stable neutral clusters with those of the corresponding charged clusters. Based on the evaporation rates of different molecules from the charged clusters, we determined the most likely resulting cluster composition when a stable neutral cluster is charged and the molecules with the highest evaporation rates are lost from it. We found that all of the most stable neutral clusters will be altered by both positive and negative charging. In the case of charging clusters negatively, base molecules will completely evaporate from clusters with 1 to 3 sulfuric acid molecules in the case of ammonia, and from clusters with 1 or 2 sulfuric acid molecules in the case of dimethylamine. Larger clusters will maintain some base molecules, but the H2SO4 : base ratio will increase. In the case of positive charging, some of the acid molecules will evaporate, decreasing the H2SO4 : base ratio.

Perfectly planar boronyl boroxine D3h B6O6: A boron oxide analog of boroxine and benzene

Inorganic benzene-like compounds such as boroxine and borazine are of interest in chemistry. Here we report on theoretical prediction of a new member of the inorganic benzene family: boronyl boroxine. This perfectly planar D3h B6O6 (1, (1)A1') cluster is identified as the global minimum of the system at density functional theory (B3LYP) and molecular orbital theory levels, which lies at least ∼20 kcal∕mol lower in energy than alternative structures. It can be formulated as B3O3(BO)3 and features a boroxol B3O3 ring as the core with three boronyl (BO) groups attached terminally, closely resembling boroxine and obtainable from the latter via isovalent BO∕H substitution. Detailed bonding analyses reveal weak π aromaticity in boronyl boroxine, rendering it a true analog to boroxine and borazine. Upon electron attachment, the slightly distorted C2v B6O6(-) (2, (2)A2) anion is also perfectly planar, and its electronic properties are calculated. A huge energy gap (4.83 eV) is predicted for B6O6(-) (2) at B3LYP level, which is characteristic of a stable closed-shell neutral cluster. Similar to benzene, boronyl boroxine is also predicted to be an effective inorganic ligand to form sandwich-type complexes, such as D3d [B3O3(BO)3]2Cr (4, (1)Ag).

Electronic structure, bonding, and properties of Sn mGe n ( m + n ⩽ 5) clusters: A DFT study

Electronic structures of tin–germanium binary clusters up to five atoms obtained by searching global optimization of the energy surface using Metropolis Monte Carlo (MMC) and genetic algorithm (GA) followed by bond strength propensity model (BSPM) and by local optimization using density functional theory (DFT) are reported. Geometries and properties of the most stable cation, neutral, and anion clusters are calculated at the B3LYP/aug-cc-pVTZ-pp level of theory. The average binding energy per atom is calculated to study its dependence on the size of the cluster. The HOMO–LUMO energy gap, ionization potential (IP), electron affinity (EA), and vertical detachment energy (VDE) are also computed for the most stable isomer of each cluster. The reactivity descriptors such as chemical potential, chemical hardness, and electrophilicity index of the lowest-energy isomers of these clusters are estimated to study their relative stabilities. The one-step fragmentation patterns of the clusters are studied to determine the relative strength of the Ge–Ge, Sn–Ge, and Sn–Sn interactions by computing the fragmentation energies. A four membered ring formed by the Sn 2Ge 2-b cluster shows π-aromaticity with a NICS(1) value of −13.2 ppm.

Stability of small Pdn (n=1–7) clusters on the basis of structural and electronic properties: A density functional approach

Density functional calculations within the generalized gradient approximation have been used to investigate the lowest energy electronic and geometric structures of neutral, cationic, and anionic Pd(n) (n=1-7) clusters in the gas phase. In this study, we have examined three different spin multiplicities (M=1, 3, and 5) for different possible structural isomers of each neutral cluster. The calculated lowest energy structures of the neutral clusters are found to have multiplicities, M=1 for Pd(1), Pd(3), Pd(5), Pd(6), and Pd(7), while M=3 for Pd(2) and Pd(4). We have also determined the lowest energy states of cationic and anionic Pd(n) (n=1-7) clusters, formed from the most stable neutral clusters, in three spin multiplicities (M=2, 4, and 6). Bond length, coordination number, binding energy, fragmentation energy, bond dissociation energy, ionization potential, electron affinity, chemical hardness, and electric dipole moment of the optimized clusters are compared with experimental and other theoretical results available in the literature. Based on these criteria, we predict the four-atom palladium cluster to be a magic-number cluster.

Density Functional Theory Study of Small Vanadium Oxide Clusters

Density functional theory is employed to study structure and stability of small neutral vanadium oxide clusters in the gas phase. BPW91/LANL2DZ level of theory is used to obtain structures of VOy (y=1-5), V2Oy (y=2-7), V3Oy (y=4-9), and V4Oy (y=7-12) clusters. Enthalpies of growth and fragmentation reactions of the lowest energy isomers of vanadium oxide molecules are also obtained to study the stability of neutral vanadium oxide species under oxygen saturated gas-phase conditions. Our results suggest that cyclic and cage-like structures are preferred for the lowest energy isomers of neutral vanadium oxide clusters, and oxygen-oxygen bonds are present for oxygen-rich clusters. Clusters with an odd number of vanadium atoms tend to have low spin ground states, while clusters with even number of vanadium atoms have a variety of spin multiplicities for their ground electronic state. VO2, V2O5, V3O7, and V4O10 are predicted to be the most stable neutral clusters under the oxygen saturated conditions. These results are in agreement with and complement previous gas-phase experimental studies of neutral vanadium oxide clusters.

Theoretical estimation of the ionization potential of water in condensed phase. II. Superficial water layers

Quantum chemical calculations of neutral and charged (H2O) n water clusters modeling fragments of a real hydrogen-bond network of water and dynamic simulations of the clusters either upon the electron removal from a stable neutral cluster or upon the excitation of various cluster vibrations enabled us to distinguish separate stages of the structure reorganization. Thermal motion of molecules in a liquid modeled by the low-frequency rotational vibrations and swinging of molecules prevents the formation of cations with the optimum mutual arrangement of the OH radical and H3O+ ion. Judging from the typical periods of reactive vibrations and those motions, which impede the desired structure reorganization, the most probable should be the formation of OH…H2O…H3O+ fragments in liquid water. The energy necessary for the ionization of superficial water layers (at the irradiation) can be estimated from the intermediate ionization potentials of water clusters. Extrapolating the dependence of these potentials on the number of water molecules constituting the cluster provided the first ever theoretical estimate of the threshold ionization energy of water: 9.5 eV.

Dynamics of water clusters upon UV‐excitation leading to ionization: Nonempirical study

AbstractNonempirical direct molecular dynamics of neutral and cationic water clusters involving four to six molecules is studied to shed light on the character of the ionization of water clusters. Potential energy and forces are calculated in the second‐order of the Møller‐Plesset perturbation theory with a 6–31++G(1d, 1p) basis set. Upon vertical ionization of a water cluster, H3O+ and OH fragments appear. The process needs no less than 40 fs, and in some cases, up to 100 or 150 fs. The resulting configuration of the cluster (neglecting its generally larger volume) is close to that obtained in the geometry optimization run. Vibrational excitation of a neutral cluster with a total energy about half its adiabatic ionization potential may promote the appearance of structures similar to that of the stable cation at certain moments in time. In particular, a configuration in which only one water molecule separates H3O+ and OH− fragments forms much faster than upon vertical electron detachment from a stable neutral cluster, in nearly 18 fs. Such structure reorganization is noticeably impeded by the rotational–vibrational excitation of the whole cluster, especially when hydrogen bonds are substantially distorted. The effect of distorting motions becomes very pronounced after 20 fs. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007

Formation and distribution of neutral vanadium, niobium, and tantalum oxide clusters: Single photon ionization at 26.5eV

Neutral vanadium, niobium, and tantalum oxide clusters are studied by single photon ionization employing a 26.5 eV/photon soft x-ray laser. During the ionization process the metal oxide clusters are almost free of fragmentation. The most stable neutral clusters of vanadium, niobium, and tantalum oxides are of the general form (MO2)0,1(M2O5)y. M2O5 is identified as a basic building unit for these three neutral metal oxide species. Each cluster family (Mm, m=1,...,9) displays at least one oxygen deficient and/or oxygen rich cluster stoichiometry in addition to the above most stable species. For tantalum and niobium families with even m, oxygen deficient clusters have the general formula (MO2)2(M2O5)y. For vanadium oxide clusters, oxygen deficient clusters are detected for all cluster families Vm (m=1,[ellipsis (horizontal)],9), with stable structures (VO2)x(V2O5)y. Oxygen rich metal oxide clusters with high ionization energies (IE>10.5 eV, 118 nm photon) are detected with general formulas expressed as (MO2)2 (M2O5)y O1,2,3. Oxygen rich clusters, in general, have up to three attached hydrogen atoms, such as VO3H1,2, V2O5H1,2, Nb2O5H1,2, etc.

Relativistic Computational Investigation: The Geometries and Electronic Properties of TaSin+ (n = 1−13, 16) Clusters

The equilibrium geometries, stabilities, and electronic properties of the TaSi(n)+ (n = 1-13, 16) clusters are investigated systematically by using the relativistic density functional method with generalized gradient approximation. The small-sized TaSi(n)+ clusters with slight geometrical adjustments basically keep the frameworks that are analogous to the neutrals while the medium-sized charged clusters significantly deform the neutral geometries, which are confirmed by the calculated AIP and VIP values. Furthermore, the optimized geometries of the charged clusters agree with the experimental results of Hiura and co-workers (Hiura, H.; Miyazaki, T.; Kanayama, T. Phys. Rev. Lett. 2001, 86, 1733). The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) gaps of the charged clusters are generally increased as the cluster size goes from n = 1 to 13; and the large HOMO-LUMO gaps of charged clusters resulting from the positive charge indicate that their chemical stabilities are stronger than their neutral counterparts, especially for n = 4, 6, and 7 clusters. Additionally, the contributions of the d orbitals of the Ta atom to the HOMO and LUMO reveal that the chemical activity of the d orbitals of the Ta atom decreases gradually as the number of silicon atoms increases. This interesting finding is in good agreement with the recent experimental results on the reactive activities of the H2O and transition-metal silicon clusters (Koyasu, K.; Akutsu, M.; Mitsui, M.; Nakajima, A. J. Am. Chem. Soc. 2005, 127, 4998). Generally, the positive charge significantly influences the electronic and geometric structures of the charged clusters. Finally, the most stable neutral and charged TaSi16 clusters are found to be fullerene-like structures and the HOMO-LUMO gap in charged form is detectable experimentally.

Geometries and Electronic Properties of the Neutral and Charged Rare Earth Yb-Doped Sin (n = 1−6) Clusters: A Relativistic Density Functional Investigation

The neutral and charged YbSi(n) (n = 1-6) clusters considering different spin configurations have been systematically investigated by using the relativistic density functional theory with generalized gradient approximation. The total bonding energies, equilibrium geometries, Mulliken populations (MP), Hirshfeld charges (HC), fragmentation energies, and highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps are calculated and discussed. The optimized geometries indicate that the most stable YbSi(n) (n = 1-6) clusters keep basically the analogous frameworks as the low-lying Si(n)(+1) clusters, while the charged species deviate from their neutral counterparts, and that the doped Yb tends to occupy the substitutional site of the neutral and charged YbSi(n) isomers. The relative stabilities are investigated in terms of the calculated fragmentation energies, exhibiting enhanced stabilities for the remarkably stable neutral and charged YbSi2 and YbSi5 clusters. Furthermore, the calculated MP and HC values show that the charges of the neutral and charged YbSi(n) clusters transfer from the Yb atom to Si(n) atoms and the Yb atom acts as an electron donor, and that the f orbitals of the Yb atom in the neutral and charged YbSi(n) clusters behave as core without involvement in chemical bonding. The calculated HOMO-LUMO gaps indicate that the YbSi2 and YbSi4+ clusters have stronger chemical stabilities. Comparisons of the Yb-doped Si(n) (n = 1-6) with available theoretical results of transition-metal-doped silicon clusters are made. The growth pattern is investigated also.

Dissociative Photodetachment Dynamics of Solvated Iodine Cluster Anions

Photoelectron-photofragment coincidence spectroscopy of I- (CO2), I- (NH3), I- (H2O), I- (C6H5NH2), and I- (C6H5OH) clusters was used to study the dissociative photodetachment (DPD) dynamics at 257 nm. Photodetachment from all five clusters was observed to yield bound neutral clusters as well as the DPD products of the iodine atom and the molecular solvent. Photoelectron images and kinetic energy spectra were recorded in coincidence with both the translational energy released between dissociating neutral products and stable neutral clusters. The variation of the photoelectron angular distributions in the clusters was measured, revealing significant perturbations relative to I- for I- (H2O) and I- (C6H5NH2). Product branching ratios for stable versus dissociative photodetachment and photodetachment to the I(2P(3/2)) and I(2P(1/2)) states are reported. The measurements reveal a dependence of the DPD dynamics on the final spin-orbit state of iodine in the cases of I- (C6H5NH2) and I- (CO2) and a threshold detachment process in I- (C6H5NH2).

A theoretical investigation on the [formula omitted] clusters by density functional theory methods

The first systematic study of the Ti ( H 2 O ) n 0 , 1 + ( n = 1 – 5 ) series of clusters is herein presented at the level of the DFT B3LYP method in conjunction with electron core potential basis sets. The investigated structures are relevant for laser-induced and laser-ablation syntheses of titanium compounds, and also for fundamental spectroscopy studies of metal-bearing species in the gas phase. Calculated properties include optimal geometries, total energies, bond lengths, bond angles, natural orbital population analysis charges, and hydration dissociation energies inter alia. Present results reveal a strict correlation between the clusters total energy and their spin state. Without exception, the most stable neutral (cation) clusters Ti ( H 2 O ) 1 – 5 0 + [ Ti ( H 2 O ) 1 – 5 1 + ] are those with spin state S = 1 ( S = 3/2). Comparisons with a few available theoretical results show good agreement.

On the Titanium Oxide Neutral Cluster Distribution in the Gas Phase: Detection through 118 nm Single-Photon and 193 nm Multiphoton Ionization

Titanium oxide clusters are generated in a supersonic expansion by laser ablation of the metal and reaction with oxygen (0.1-6%) in He expansion gas. Mass spectra of the titanium oxide clusters are observed by photoionization with lasers of three different wavelengths: 118, 193, and 355 nm. Only the 118 nm (10.5 eV) light can ionize Ti(m)O(n) neutral clusters without fragmentation. Both the 193 nm (6.4 eV) and 355 nm (3.5 eV) multiphoton ionization cause fragmentation of the neutral clusters during the ionization process and, thus, can complicate the determination of the stable neutral Ti(m)O(n) gas-phase species. Employing 118 nm single-photon ionization and line-width data, the Ti(m)O(2m) and Ti(m)O(2m+1) series are found to be the most stable neutral cluster species for high oxygen content in the expansion gas. Fragmentation during the multiphoton ionization process for 193 nm light yields the cluster ions Ti(m)O(2m-1,-2)+. These ions are formed by the loss of one or two oxygen atoms from Ti(m)O(2m,2m+1) neutral species. The dominant cluster growth process is suggested to be through the addition of TiO2 species. For low oxygen content (<2%) in the expansion gas, oxygen-deficient clusters of the form Ti(m)O(2m-1,-2) are also observed. These latter series are not fragmented by the 193 nm ionization process.