An ab initio molecular dynamics method was used to compare the ionic dissolution of soluble sodium chloride (NaCl) in water clusters with the highly insoluble silver chloride (AgCl). The ...investigations focused on the solvation structures, dynamics, and energetics of the contact ion pair (CIP) and of the solvent‐separated ion pair (SSIP) in NaCl(H2O)n and AgCl(H2O)n with cluster sizes of n = 6, 10 and 14. We found that the minimum cluster size required to stabilize the SSIP configuration in NaCl(H2O)n is temperature‐dependent. For n = 6, both configurations are present as two distinct local minima on the free‐energy profile at 100 K, whereas SSIP is unstable at 300 K. Both configurations, separated by a low barrier (<10 kJ mol−1), are identifiable on the free energy profiles of NaCl(H2O)n for n = 10 and 14 at 300 K, with the Na+/Cl− pairs being internally solvated in the water cluster and the SSIP configuration being slightly higher in energy (<5 kJ mol−1). In agreement with the low bulk solubility of AgCl, no SSIP minimum is observed on the free‐energy profiles of finite AgCl(H2O)n clusters. The AgCl interaction is more covalent in nature, and is less affected by the water solvent. Unlike NaCl, AgCl is mainly solvated on the surface in finite water clusters, and ionic dissolution requires a significant reorganization of the solvent structure.
The minimum size of a water cluster required for the ionic dissolution of a salt molecule is temperature‐dependent. NaCl is ionized and internally solvated in a water cluster, while covalent AgCl is solvated on the cluster surface.
Nanodroplets that contain hydrated electrons provide information complementary to standard radiolysis techniques. Although the reaction of hydrated electrons with acetonitrile was observed in ...solution 25 years ago, its product has only now been identified in a gas‐phase experiment as the hydrogen adduct. The picture shows a solvent‐stabilized radical anion, which is suggested as a reactive intermediate.
Die Entwicklung der Psychiatrie im Deutschland des 20. Jahrhunderts war von Radikalität, Stagnation und Reformwillen gleichermaßen geprägt. Dieser Band präsentiert aktuelle Forschungsergebnisse zur ...psychiatrischen Praxis und ihren Institutionen vom Kaiserreich bis zur Deutschen Einheit. Der Alltag von Psychiatriebetroffenen im Spiegel der Entwicklung der Anstalten und die Veränderung therapeutischer Ansätze werden dabei ebenso analysiert wie die Perspektive der Patienten, ihrer Angehörigen und der Öffentlichkeit auf die Psychiatrie.Die fundierte Bestandsaufnahme bietet einen facettenreichen Blick auf die Brüche und Kontinuitäten der deutschen Geschichte psychiatrischen Handelns.
Hydrated singly charged zinc cations Zn (H2O)n, n approximately 6-53, were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Black-body radiation induced dissociation ...results exclusively in sequential loss of individual water molecules. In the reaction of Zn+ (H2O)n with gaseous HCl, Zn is oxidized and hydrogen reduced when a second HCl molecule is taken up, leading to the formation of ZnCl+ (HCl)(H2O)n-m cluster ions and evaporation of atomic hydrogen together with m H2O molecules. The results are compared with earlier studies of Mg+ (H2O)n, for which hydrogen formation is already observed without HCl in a characteristic size region. The difference between zinc and magnesium is rationalized with the help of density functional theory calculations, which indicate a distinct difference in the thermochemistry of the reactions involved. The generally accepted hydrated electron model for hydrogen formation in Mg+ (H2O)n is modified for zinc to account for the different reactivity.
Gas-phase reactions of anionic and cationic rhodium clusters with azidoacetonitrile are studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry under near-thermal conditions. ...All anionic and large cationic clusters react by adding C2,N2 in consecutive steps, either by forming interstitial carbides and nitrides or by adding two CN groups to the cluster surface. Small cationic clusters behave differently, with the unimolecular decomposition of the azide determining the reactivity. Saturation is identified via the size-dependent efficiency of consecutive reaction steps. The present results are the first study of organic azides on transition metal clusters. The observed selectivity of the reaction is in contrast to the high exothermicity of any reaction with azide species. The cationic cluster reactivity shows a gradual transition from gas-phase to surface-like behavior with increasing cluster size.
► In this study we model the adsorption of the superheavy element 113 on gold surfaces. ► The binding energy of element 113 and thallium is calculated for cluster models. ► For many different binding ...sites, element 113 binds weaker by 90±15kJ/mol.
The adsorption of thallium and element 113 atoms on a gold surface has been modelled by cluster calculations. Quasirelativistic two-component density functional calculations that include spin–orbit coupling self-consistently have been used together with spin-dependent effective core potentials. The validity of this method is demonstrated by comparisons with high-level wave function based calculations on the hetero-dimers AuTl and Au(113). New basis sets had to be generated because standard basis sets optimized for scalar-relativistic calculations are too inflexible to describe the different behaviour of the atomic sub-shells that result from the spin–orbit interaction. The topmost layer of gold atoms within the cluster was allowed to fully relax upon adsorption, and different adsorption sites (on-top, hollow, and bridge) on the (100) and (111) surfaces were considered. Spin–orbit coupling reduces the surface binding energies of an element 113 atom much more than it does for Tl, such that the binding energy of element 113 to the gold cluster, as compared to Tl, is reduced by 90±15kJ/mol in most cases. Together with the experimental result for thallium, this allows an estimate of the adsorption temperature of element 113 in thermochromatography experiments.
A route to efficient generation of C6H4+*, potentially the benzyne radical cation, is presented. Laser vaporization of Mg+* and supersonic expansion in helium doped with o-, m-, or p-C6H4F2 yields, ...among other ions, o-, m-, p-C6H4F2Mg+* complexes, but no C6H4+*. Collision-induced dissociation experiments show that the o-C6H4F2Mg+* complex can be converted into C6H4+* in a mildly energetic collision, with a center-of-mass energy around 1-2 eV. These conditions can also be reached in the ion source when argon is used as a carrier gas. In this way, mass spectra containing the desired m/z 76 peak, i.e. C6H4+*, are obtained.
An H/D-exchange reaction involving the methyl group of acetonitrile is observed in the small anionic water cluster OH-(CD3CN)(H2O)2. In this cluster, a randomization of H and D atoms takes place, and ...in subsequent collisions with CD3CN, the potentially partially deuterated acetonitrile is replaced by the fully deuterated species. In sequential collisions, fully deuterated clusters OD-(CD3CN)(D2O)2 are obtained as final products. The H/D-exchange does not occur in OH-(CD3CN)(H2O)3 or larger clusters. Density functional calculations show that in these larger species, the OH- no longer directly attacks the methyl group, and the barriers for H/D-exchange become higher than those for ligand loss reaction channels. This is a very subtle influence of solvation on an H/D-exchange reaction in the gas phase, where a relatively acidic methyl group encounters a strongly basic reaction partner.
