Calculation of spectral characteristics of water clusters upon interaction with oxygen molecules and bromine ions

Interactions of (Br⁻) _i (H₂O)_50−i clusters (0 ≤ i ≤ 6) with molecular oxygen is studied by the molecular dynamics method using flexible molecule model. Values of real and imaginary parts of permittivity decrease in the 0 ≤ ω ≤ 3500 cm⁻¹ frequency range with increasing number of bromine ions in a cluster. The ability of cluster to absorb IR radiation decreases, whereas the reflectance and Raman light scattering remains nearly unchanged. An increase in the content of Br⁻ ions in the cluster lowers the power of emitted IR radiation and decreases the amount of active electrons participating in the interaction with IR radiation. However, when the concentration of Brions becomes substantially higher (at i = 5 and 6), the values of emitted power and the number of active electrons are restored to the values that are typical for water cluster in the absence of Br⁻ ions. At i ≥ 3, repelling Br⁻ ions acquire kinetic energy, which is sufficient to remove molecular oxygen from the system.     

Molecular dynamics calculation of spectral characteristics of water clusters in the presence of ozone molecules and chlorine ions

Simultaneous interaction of the (H₂O)₅₀ cluster with O₃ molecules and Cl⁻ ions was studied by the molecular dynamics method. Six O₃ molecules located near the cluster were absorbed by the aqueous aggregate, and Cl⁻ ions in turn left the zone of the interaction with the cluster. Some of Cl⁻ ions penetrated inside the formed (O₃)₆(H₂O)₅₀ cluster and come into collision with O₃ molecules that split the ozone molecule into atoms. When Cl⁻ ions were removed sufficiently far away from the cluster, the water cluster with absorbed O₃ molecules and O atoms was observed for 15.6 ps. The interaction of water molecules with Cl⁻ ions gives rise to an increase in the integral intensity of absorption and emission IR spectra, and also to an essential decrease in the analogous characteristics of the Raman spectrum in the frequency range of 0 ≤ ω ≤ 1000 cm⁻¹. The presence of Cl⁻ ions did not affect essentially the location of the main band in the IR spectra, but considerably changed the shape of the bands in the Raman spectrum.     

Spectral characteristics of water clusters in the presence of nitrate ions

Nitrate ion adsorption by water clusters is studied using the molecular dynamics method combined with a polarizable model of flexible molecules. It is established that successive addition of one to six NO ₃ ^? ions to an (H₂O)₅₀ cluster decreases the averaged electrical potential related to the center of masses of water molecules. The (H₂O)₅₀ cluster retains its thermodynamic stability, provided that no more than three nitrate ions are added to it. After NO ₃ ^? ions are adsorbed, the real and imaginary components of the dielectric permittivity and the intensity of the Raman spectrum decrease, while the intensity of the IR absorption spectrum increases. Moreover, ion adsorption by the water cluster reduces the IR absorption coefficient and refractive index.     

Molecular dynamic study of thermodynamic properties of water clusters containing sodium or chlorine ions

The molecular dynamic method with design is used to calculate the thermodynamic properties of isolated water clusters containing Na⁺ or Cl^-. The number of water molecules in the clusters is from 2 to 14. The size dependence of the microscopic analogs of pressure, isothermal compressibility, and surface tension of the clusters is determined. The effect of positive and negative ions on heteromolecular nucleation in vapor is discussed. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 6, pp. 1092–1102, November–December, 1997.     

Spectral characteristics of water clusters in the presence of nitrogen dioxide

The absorption of NO₂ molecules by a water cluster containing 25 molecules was studied by molecular dynamics. The calculated dielectric characteristics of a system of (NO₂) _i (H₂O)₂₅ clusters (1 ≤ i ≤ 6) were compared with similar data for a cluster system of pure water. The ability of the disperse water system that trapped NO₂ molecules to absorb IR radiation increased, and the rate of the absorbed energy emission decreased. The Raman spectrum of the disperse system that absorbed NO₂ molecules changed most significantly in the low-frequency range. The emission time of cluster-generated radiation was much smaller than the lifetime of the clusters.     

Chemiionization upon reaction of sodium clusters with molecular oxygen

Crossed beam reaction of Na _x (x<11) with O₂ under single collision conditions leads to the selective and spontaneous formation of significant amounts of Na₅O₂ ⁺ and Na₃O⁺.     

Quantum-mechanical simulation of the interaction of aluminum- and boron-containing zeolite clusters with molecules of water and ammonia

Quantum-mechanical computations of zeolite clusters with molecules of water and ammonia have been carried out. The clusters consisted of ten atoms of silicon and aluminum, where one atom of aluminum was also replaced with an atom of boron. Values of the bond length and bond angles have been obtained; the geometry of adsorption complexes and the bond energy for molecules of water and ammonia with atoms of aluminum and boron of a zeolite fragment have been determined. The computed values of bond energy for molecule probes yield the quantitative strength characteristic of zeolite aprotic acid centers.     

Revisiting small clusters of water molecules

The geometries and relative energies of small clusters of water molecules, (H₂O)_n with 4 ⩽ n ⩽ 8, are reported. For each value of n we have considered the conformations corresponding to the lowest-energy minimum and those in nearby relative minima. Thus we report on six tetramers, four pentamers, six hexanlers, four heptamers, and eigth octamers. The geometrical conformations have been obtained using the Metropolis Monte Carlo method as a minimization technique, where the interaction energy is computed with the MCY potential plus three- and four-body corrections previously discussed. All the reported structures for a given cluster size are found to be close in energy. For the lowest conformation the geometry was optimized with ab initio SCF computations using energy gradients. Our results are compared with previous theoretical studies. We discuss the convergence of the interaction potential for liquid water when expressed in terms of a many-body series expansion.     

Lanthanide clusters with internal Ln ions: highly emissive molecules with solid-state cores

"Er(SePh)(2.5)I(0.5)" reacts with elemental S to give (THF)10Er6S6I6, a double cubane cluster with one face of the Er4S4 cube capped by an additional Er2S2. Reactions with a mixture of elemental S/Se results in the formation of (THF)14Er10S6(Se2)6I6, a cluster composed of an Er6S6 double cubane core, with two "Er2(Se2)3" units condensed onto opposing rectangular sides of the Er6S6 fragment. This deposition of Er2Se6 totally encapsulates the two central Er with chalcogen atoms (4 S, 4 Se) and excludes neutral THF donors or iodides from the two primary coordination spheres. The Er10 compound is the first lanthanide cluster to contain internal, chalcogen encapsulated Ln. This cluster shows strong fluorescence at 1544 nm with a measured decay time of 3 ms and an estimated quantum efficiency of 78%, which is comparable to Er doped solid-state materials. The unusual fluorescence spectral properties of (THF)14Er10S6Se12I6 are unprecedented for a molecular Er complex and are attributed to the low phonon energy host environment provided by the I-, S(2-), and Se2(2-) ligands.     

The spectral characteristics of chlorine-containing water clusters in the presence of ozone and oxygen

The infrared absorption and Raman spectra were calculated by the molecular dynamics method for water clusters with chlorine ions in a medium of water and ozone or oxygen molecules. The intensity of IR absorption spectra of clusters with absorbed oxygen increased and that of clusters with absorbed ozone decreased as the number of chlorine ions grew. Excitation strengthening caused by an increase in the number of Cl⁻ ions weakened the intensity of Raman spectra when either oxygen or ozone was absorbed; for ozone, this weakening was more noticeable.     

Radiometric determination of ionic chlorine and oxygen in water

Two portable devices for the radiometric analysis of industrial water are described. Chlorides are precipitated by a known volume of standard silver nitrate labelled with^110mAg; the decrease of activity is proportional to the amount of ionic chlorine. Determination of dissolved oxygen is achieved by dissolution of radioactive thallium, and the activity of the effluent is directly related to the concentration of oxygen.     

Theoretical study of the interaction of molecular oxygen with copper clusters

A new method based on frontier orbital theory has been used to investigate the binding site of molecular oxygen to neutral and anion copper clusters. It has been shown that one can make useful predictions of the binding sites based on the knowledge of the donor local reactivity of the cluster using the condensed Fukui function, f(-)(Ff). In this way, it was found that Cu(3), Cu(5), and Cu(5)(-) have the highest reactivity toward molecular oxygen.     

Density functional study of the interaction of chlorine atom with small neutral and charged silver clusters

Chlorine adsorption on small neutral, anionic, and cationic silver clusters Ag(n) (n=2-7) has been studied using the PW91PW91 density functional method. It was found that the adsorption of chlorine on the lowest-energy bare clusters does not always produce the lowest-energy complexes. In addition, the binding of chlorine can greatly change the geometries of the silver clusters in some cases. Among various possible adsorption sites, bridge site is energetically preferred for the neutral Ag(n) while top site is energetically more preferred for the anionic Ag(n) with n< or =6. For cationic clusters, adsorptions on bridge and face sites have similar binding energies, which are much larger than those on top sites. Natural bond orbital analyses show that irrespective of charge state, electrons always transfer from silver atoms to adsorbate and silver acts like alkali metals in the interaction with chlorine atom. Significant odd-even alternation patterns in the properties of the complexes have been observed: Even-electron clusters often have higher ionization energies, lower electron affinities, and higher dissociation energies than their odd-electron neighbors. It was also found that chlorine atoms bind more strongly with odd-electron bare clusters than with even-electron bare clusters. These patterns reveal that even-electron clusters are more stable than odd-electron clusters.     

Amino-acid and water molecules adsorbed on water clusters in a beam

Water clusters (H2On and (D2On (n相似文献   

Linear molecules based on dimethylgermanium and dimethylsilicon groups bridged with oxygen atoms and terminated with chlorine atoms

This article deals with the equilibrated system (CH₃)₂SiCl₂–(CH₃)₂GeCl₂–[(CH₃)₂SiO]–[(CH₃)₂GeO], which consists of a range of various chain, and some ring, molecules resulting from scrambling of the bridging oxygen with the monofunctional chlorine atoms between the dimethylgermanium and dimethylsilicon moieties. The proton nuclear magnetic resonance of the methyl groups (which do not exchange appreciably under the conditions employed) bonded to the germanium and silicon atoms shows that there is a strong preference of the chlorine atoms for being on the dimethylgermanium and the bridging group for being on the dimethlysilicon moiety at equilibrium. This means that thermodynamic factors alone cause the germanium atoms to be found as “unreacted” dimethyldichlorogermane with siloxane polymers or to be preferentially arranged at the ends of the chain molecules in the case of the mixed germoxane–siloxanes. The NMR fine structure is interpreted in these terms, and it is shown that the experimental data may be fitted by appropriate calculations based on only four equilibrium constants, which define the arrangement of neighboring atoms about any given atom in a molecule and the size distribution of the linear molecules.