bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic Structure of LinHn Clusters
Authors: Dugourd Ph. , Rayane D. , Vezin B. , Chevaleyre J. , Broyer M. , Labastie P. 
Published: July 2012

AbstractThe LinHm clusters are produced in a seeded molecular beam. The lithium vapor is expanded in the vacuum with a mixture of 99% of argon and 1% of H2. The formed clusters are analyzed by a time of flight mass spectrometer and the clusters electronic structure is probed through ionization potential measurements. The electronic structure of LinH and LinH2 may be interpreted by assuming that the bonding of one hydrogen atom localizes one electron of the lithium atoms and that the other electrons remain delocalized.
Theory for the Polarization Interaction between an Excess Electron and a Cluster of Polar Molecules
Authors: Stampfli P. , Bennemann K. H. 
Published: July 2012

AbstractThe polarization interaction between an excess electron and a cluster of polar molecules is discussed in a microscopic model and related to the dielectric continuum model. We obtain that the polarization of the bound electrons strongly reduces the strength of the interaction between the excess electron and the molecules by an effective screening. Previous calculations of the electronaffinity of clusters of polar molecules have used pair‐potential interactions, which neglect these screening terms. Thus the attractive polarization energy has been overestimated, resulting in much larger vertical detachment energies than observed in the experiment.
Photoelectron Spectroscopy of Clusters and Adsorbates on Clusters
Authors: Cha Chia‐Yen , Ganteför Gerd , Eberhardt Wolfgang 
Published: July 2012

AbstractThe electronic and geometric structure of free metal cluster anions is studied by photodetachment. The cluster anions are produced in a PACIS (Pulsed Arc Cluster Ion Source). From mass separated bunches of anions electrons are detached by a UV‐laser pulse. Photoelectron spectra of the detached electrons are measured with a “magnetic bottle” type time of flight spectrometer. First data on Ga clusters are presented and compared to similar measurements on Al clusters. At the high resolution (∽ 30 meV) accessible with this experimental set up comparison of the data with calculations delivers new insights into the geometric structure of the particles. A first application of this technique to molecules adsorbed on metal clusters is presented.
Complex Electron Affinity Processes in Clusters of S and Si
Authors: Von Niessen W. , Zakrzewski V. G. 
Published: July 2012

AbstractVertical and in some cases adiabatic electron affinities are calculated for the clusters S4 and Sin, n = 3 – 7 with large basis sets. The effects of electron correlation are taken into account by CI and Green function techniques. The clusters show a complex behaviour upon electron attachment. The isomers of 84 show normal electron capture processes as well as electron attachment with shake‐up. The Si clusters show multiple affinity states resulting from capture of an electron into different orbitals: Si3 C2v has at least three, Si4 D2h four, Si5 D3h two, Si6 D4v one, Si6 C2v three and Si7 D5h two affinity states (vertical processes: Sin + e− ± Sin + hν). For the Sin clusters in some cases shake‐up affinities are calculated which are positive. The effects of electron correlation on the electron affinities are extremely large for the Si clusters in particular. In several cases the differences between the adiabatic and vertical electron affinities are very large amounting up to 1.5 eV.
Theory for the Magnetic Properties of a Free Metal Cluster Ensemble
Authors: Jensen P. J. , Bennemann K. H. 
Published: July 2012

AbstractThe magnetization and the deflection profiles of an ensemble of free magnetic metal clusters in an inhomogeneous external magnet field are calculated. If a weak lattice anisotropy is present, as expected for 3d‐transition metal clusters, one obtains superparamagnetic behavior. If strong anisotropy is present, as might be the case for rare earth metal clusters, a smaller magnetization compared to superparamagnetism is obtained. A symmetric deflection profile is obtained for the case of vanishing anisotropy, but gnerally no longer if an anisotropy is present. Effects due to a low cluster Curie temperature comparable to the cluster temperature and cluster rotation are also discussed.
The Ferromagnetism of Iron and Nickel Clusters in a Molecular Beam
Authors: Becker J. A. , De Heer W. A. 
Published: July 2012

AbstractThe magnetic properties of small FeN and NiN clusters are studied in a molecular beam by their Stern Gerlach deflections. The magnetization of the particles is measured as a function of applied magnetic field H, size N and vibrational temperature Tvib (≈︁ 200‐1300 K). The intrinsic magnetic moments per atom μ at T ≈︁ 300 K are 2.2 μB for Fe130 and 0.5 μB for Ni560. A bulk‐like magnetization curve is found for Ni560 and for Fe130 at Tvib ≈︁ 1000 is found to be only slightly reduced compared with its low temperature value. The results are compared with the Heisenberg model. Anomalously low magnetization for strongly cooled FeN clusters (N = 120‐140) is found to be related to the rotational speeds. The distinct roles of rotational and vibrational temperatures for the ferromagnetism of isolated Fe clusters are rationalized in a model.
Electronic Spectra. Experimental vs. Semiclassical Electronic Spectra of Spectra of Naphthalene · Arn van der Waals Clusters
Authors: Troxler Thomas , Leutwyler Samuel 
Published: July 2012

AbstractClassical molecular‐dynamics and Monte Carlo simulations were employed to study the structures, dynamics, vibrational power spectra and electronic spectra of naphthalene · Arn clusters. Theoretical electronic absorption spectra were calculated using the spectral density formalism of Mukamel et al.; a brief review of the formalism is given together with a simple application example for the naphthalene · Ar2 complex. The experimental R2PI spectra for the series of naphthalene · Arn clusters with n = 13 – 15 are discussed on the basis of the calculated spectra. The system is shown to undergo a wetting/nonwetting transition.
Impurity Doped Simple Metal Clusters: Optical Response
Authors: Koretsky Geoffrey M. , Dahlseid Tina A. , Pollack Stuart , Chris Wang C. R. , Alameddin George , Hunter Joanna , Cameron Douglas , Liu Shengzhong , Kappes Manfred M. 
Published: July 2012

AbstractExisting and future measurements of the optical response properties of monodoped simple metal clusters are discussed.
Structure, Energetics, Dynamics. Structure and Dynamics of Size Selected Molecular Clusters
Authors: Buck Udo 
Published: July 2012

AbstractBy combining the method of size selection of clusters by momentum transfer in a scattering experiment with atomic beams with the absorption of infrared photons from a laser, the photodissociation spectra of weakly bound clusters have been measured as a function of cluster size. From the measured lineshift and linewidth, which depend sensitivily on the cluster size, the excited mode and the investigated species detailed information on the structure and the decay dynamics is obtained by accompanying calculations. Results are presented for clusters of methanol and acetonitrile as case studies.
Theoretical Treatment of Sodium Chloride Clusters
Authors: Ahlrichs Reinhart , Ochsenfeld Christian 
Published: July 2012

AbstractResults of a systematic study of structure and energetics are reported on the SCF level and with inclusion of electron correlation (MP2 and CPF). The stoichiometric systems NanCln for n = 1–6, 8, 9, 12, 15, 18, 32, and the sodium excess systems Na14Cl13 and Na18Cl17 were considered in detail. The stoichiometric systems prefer geometric arrangements as in the solid state lattice whenever possible. The sodium excess systems show an electron at an anion defect location (F‐center) or localize the electron at a sodium atom (no surface states), in either case preferably in a corner position.
Associates, Clusters, Intermolecular Complexes, Supramolecular Systems: Van der Waals Species
Authors: Hobza Pavel , Zahradnik Rudolf 
Published: July 2012

AbstractThis is an article summarizing theoretical studies carried out recently in our laboratory on van der Waals (vdW) species. In contrast to classical molecules, theoretical structure elucidation of vdW molecules nearly always represents a challenge for computational chemists. Results on molecule‐molecule complexes (e.g., (H2)2, benzene and benzyne complexes with rare gas atoms, benzene dimer, purine‐pyrimidine complexes) and ion‐molecule complexes (e.g., H, radical cations of dimers of alkyl halogenides and of alkylated and arylated water) are reviewed. The importance of study of the intersystem vibrational degrees and the role of molecular dynamics in the field of vdW systems in outlined.
Study of Electron Correlations in Pb‐Clusters
Authors: Pastor G. M. , Reindl S. L. 
Published: July 2012

AbstractThe ground state properties of Pb‐clusters are investigated using a many‐body Hamiltonian with intra and inter‐atomic Coulomb interactions. By solving the model exactly we obtain that Pb is metastable (lifetime τ > 1040s) and that it has isosceles geometry (bondangle Θ ≃ 124°). The importance of electron correlations for the stability of doubly charged clusters is discussed. By comparison between the exact solution and several variational approaches we particularly show that both the metastability and isosceles shape of Pb result mainly from antiferromagnetic quantum spin‐fluctuations.
Rapid Approximate Calculation of Numbers of Quantum States W(E,J) in the Phase Space Theory of Unimolecular Bond Fission Reactions
Authors: Olzmann M. , Troe J. 
Published: July 2012

AbstractA facile and rapid approximation for counting numbers of quantum states W(E,J) is described for application in the phase space theory of unimolecular bond fission reactions. The method accounts for J‐conservation. It is based on an empirical interpolation between analytical expressions of W(E,J) in the low J‐ and high J‐limits, and it is checked by extensive accurate state counting for sets of representative model molecules.
The Use of a Flashlamp‐Pumped Dye Laser for Single‐Pulse Spontaneous Raman Scattering in Flames
Authors: Prucker S. , Meier W. , Plath I. , Strieker W. 
Published: July 2012

AbstractA Raman scattering system based on a commercially available, high power flashlamp‐pumped dye laser is presented. Single‐pulse measurements of the temperature and major species concentrations in a stable laminar methane/air flame and in a weakly turbulent H2/air diffusion flame have been performed to assess the measuring precision and detection efficiency of this system. The problem of spatial resolution is discussed and — in this context — the advantages of combined Raman/2D LIF measurements are demonstrated.
The Anodic Growth and the Stability of Thin Passive Films on Titanium Electrodes
Authors: Müller A. , Popkirov G. S. , Schindler R. N. 
Published: July 2012

AbstractThe growth of thin passive oxide films on titanium was investigated in 1 M sodium hydroxide and in 0.5 M sulphuric acid solution. Potentiodynamic and galvanostatic experiments were carried out with simultaneous microbalance measurements to follow mass changes associated with the processes at the electrode. In addition ac impedance data were collected at different stages of the oxidation in a wide frequency range. — In alkaline electrolyte oxide growth leads to the expected mass gain of the electrode due to oxygen ion incorporation. Also the total impedance of the electrode decreases continously with increasing film thickness. In acidic environment oxide electroformation is accompanied by different dissolution processes, one of which is a potential independent chemical dissolution. The initially observed mass gain of the electrode during oxidation switches over at potentials of oxygen evolution to a total mass decrease. This effect is also reflected in the impedance measurements by a pronounced change in the total capacitance Ct plotted as function of the oxidation potential. It is suggested that this electrochemical behaviour is related to changes in the thin oxide film structure and/or composition. The results are discussed in the context of observations obtained in experiments using other experimental techniques.
tert‐Butanol as an OH‐Scavenger in the Pulse Radiolysis of Oxygenated Aqueous Systems
Authors: Piechowski Magnus Von , Thelen Marie‐Anne , Hoigné JüRg , Bühler Rolf E. 
Published: July 2012

AbstractThe application of tert‐butanol as an OH scavenger in aqueous, oxygenated solutions was studied by pulse radiolysis and computer simulation of the entire reaction mechanism. In such systems, the initially produced tert‐butanol radical (· Rtb) reacts with O2 with a rate constant of k = 1.4 · 109 M−1 s−1. The UV absorption‐spectrum of the resulting tert‐butanol peroxy‐radical, · OOR,tb, was determined. The rate constant for its dimerization, 2 · OORtb RtbO4Rtb, is k = 1.8 · 108 M−1 s−1. The formation of HO2 from the decay of RtbO4Rtb has often been neglected in earlier studies. Our reinvestigation showed a yield of 5 ± 2%. In deoxygenated systems we confirmed the rate constant for · Rtb dimerization to be k = 6 · 108 M−1 s−1.The UV spectrum of · Rtb was determined to be slightly different from literature data.
Phase Transitions in Dimethylammonium Tetrafluoroborate and Molecular Motions in Its Ionic Plastic Phase Studied by 1H and 19F NMR, Thermal Measurements, and X‐Ray Powder Diffraction Techniques
Authors: Ishida Hiroyuki , Iwachido Tadashi , Ikeda Ryuichi 
Published: July 2012

AbstractThree solid phases of (CH3)2NH2BF4 were found between 200 K and the melting point (375 K) by differential thermal analysis, differential scanning calorimetry, and 1H and 19FNMR measurements. The highest‐temperature solid phase obtainable above 283.5 K was shown to be an ionic plastic phase, where the cations as well as the anions perform rapid translational self‐diffusion and isotropic reorientation about their center of gravity. The crystal in this phase was revealed to form a CsCl‐type cubic structure with α = 5.35 Å at ca. 290 K by powder X‐ray diffraction. The two phase transitions, from the lowest‐temperature phase to the intermediate one and from the intermediate phase to the highest temperature phase, successively occur at nearly the same temperature of 283.5 ± 0.5 K. The intermediate phase could be clearly observed as an undercooled state.
TEM/EDX‐Microanalysis of Ferrite/Titanate Interfaces
Authors: Haberkern M. , Nicoloso N. , Brook R. J. 
Published: July 2012

AbstractFerrite/titanate interfaces, prepared by the co‐sintering (1400 K; 2 h) of laminates formed from tape cast (Ni,Zn)Fe2O4 and MgTiO3, have been investigated by combined TEM and EDX‐analysis. Reaction between the starting materials leads to a < 3 μm thick layered interface consisting of a cation exchanged spinel phase Mg1+xFe2‐2xTixO4, x = 0.66, and a pseudobrookite phase, MgxFe2‐2xTi1+xO5 phase with x = 0.75. As expected for this sintering time and temperature, the interface constitution is controlled by the appropriate thermodynamic relationships, favouring solid solution.
Towards a First‐Principles Thermodynamics of Solids Plenary Lecture
Authors: De Fontaine D. , Wolverton C 
Published: July 2012

AbstractTotal energy density‐functional methods have made it possible to calculate, from first principles, such important properties as cohesive energies, lattice constants and elastic moduli for elemental crystals and perfectly ordered compounds. Real solids are imperfect, however, so that lattice vibrations and compositional disorder lead to entropy contributions, vibrational and configurational. When these effects are included in an appropriate manner, properties of real crystals can be computed ab initio as a function of temperature and concentration. Consequently, it is possible to obtain, virtually from the knowledge of atomic numbers alone, such basic thermodynamic properties as free energies, entropies, heats of formation, and lattice parameters for stable and metastable phases, leading, for example, to the successful computation of certain classes of phase diagrams. Recent progress in field will be reviewed.
Structure and Electronic Properties of Complex Solids
Authors: Freeman A. J. 
Published: July 2012

AbstractDramatic advances in computational chemistry and materials science have generated an excitement, enthusiasm and fervor among its practitioners not seen for many decades. There has now been achieved a high level of reliability concerning predictions of physical and chemical properties and phenomena – thanks in large part to the continued rapid development and availability of computing power (and its easy accessibility) and the new computational methods/algorithms which this permitted to be generated. A prime area continues to be electronic structure theory where new computational/theoretical methods have been developed that permit highly precise solutions of complex many body systems at the level of the local density approximation. This talk illustrates some aspects of the present state of the field by means of several examples, notably aluminum intermetallics and semiconductor heterojunctions.
Host Lattice Electronic Properties of Hydrated Layered Intercalation Compounds Studied by Solid State 1H NMR
Authors: Lobert M. , Müller‐Warmuth W. , Katzke H. , Schöllhorn R. 
Published: July 2012

AbstractSolid state 1H NMR methods have been applied to study local magnetic fields at the proton sites of water molecules intercalated together with alkali cations in layered transition metal dichalcogenides. The chemical shift anisotropy of the Ax(H2O)y[MX2] compounds (A = Na, K; M = T1, V, Nb, Mo, Ta, W; X = S, Se) depends greatly on M and on the reduction degree x. It appears to be proportional to the anisotropic Pauli paramagnetic susceptibility and to the host material density of states at the Fermi level. For the intercalation compounds of TiS2 and NbS2 the structure of the d band has been determined. The “rigidband model” could be confirmed. Exceptional results for TaS2 and MoS2 host lattices are discussed.
Application of the Zintl‐Concept to Equilibrium Gaseous Molecules
Authors: Poth Lutz , Weil Konrad G. 
Published: July 2012

AbstractWe report on mass spectrometric investigations of the equilibrium vapor of intermetallic compounds or over heterogeneous mixtures of metals and salts. We give examples for intermetallic gaseous compounds which are representatives of the following classes of Zintl molecules: Molecules containing polyanions, molecules with Zintl anions, and molecules with Zintl cations. The latter are found in the systems antimony/tellurium/chlorine and antimony/tellurium/bromine. Details about the experiments in which the cation containing molecules are detected are given.
Investigation of the Electronic Structure of Oxocuprates by Photoelectron Spectroscopy
Authors: Adler P. , Simon A. 
Published: July 2012

AbstractThe oxocuprates Y2BaCuO5 and Bi2CuO4 the crystal structures of which contain discrete CuO5 and CuO4 units, respectively, have been investigated by angle integrated photoelectron spectroscopy. The Cu 2p core level and Cu L3VV Auger spectra are analysed within a simple cluster configuration interaction model. The experimental data and model parameters, namely the charge transfer energy Δ, the transfer integral T, and the correlation energy U as well as the main valence band features are similar as for oxocuprates with extended copper oxygen network.
Correlation between the Electrostatic Potential and the Occupation of Interstitial Sites by Hydrogen in Metallic Systems
Authors: Philipp Sabine , Leiberich Ricarda , Schmidt Peter C. , Weiss Alarich 
Published: July 2012

AbstractThe electrostatic crystal potentials V(r) of the cubic metals Pd, V, Nb, Ta, and the intermetallic phases FeTi and XEr, X = Cu, Ag, Au, have been determined by the full potential augmented‐plane‐wave method (FP‐APW). Furthermore, to study the electronic states in dilute metal‐hydrogen‐systems the partial densities of states have been calculated by the supercell procedure using the augmented‐spherical‐wave method (ASW) for PdH1/32. The results are compared with the values for PdH1/4, PdH, and Pd. – A relation is found between the depth of the host lattice electrostatic potential and the occupation of interstitial lattice sites by hydrogen in the metal‐hydrogen α‐phases. For bcc V, Nb, and Ta the crystal potential “seen” by a proton has its deepest minimum at the tetrahedral site, for fcc Pd the minimum occurs at the octahedral site and in FeTi (B2‐type) the minimum of Vproton(r) is found for the octahedral site surrounded by 2 Fe atoms and 4 Ti atoms. In all these cases the calculated site of the minimum is in accordance with the location of hydrogen in the respective α‐phases found experimentally by neutron scattering. For XEr. X = Cu, Ag, Au, a preferred occupation by hydrogen is predicted.
Magnetic Properties of Iron(II)‐Cyclo‐Tetraphosphate Fe2P4O12
Authors: Gunßer W. , Röhl B. R. , Schütze A. , Gmelin E. , Wiedenmann A. 
Published: July 2012

AbstractPolycrystalline samples of iron(II)‐cyclo‐tetraphosphate were prepared and the magnetic properties were investigated using magnetic susceptibility, magnetization and heat capacity measurements. The Curie‐Weiss law is obeyed down to ca. 240 K and a paramagnetic Curie temperature Θp of 28 K was obtained. Susceptibility‐ and heat capacity mesurements revealed a Curie‐temperature TC of 17 K. Furthermore, the heat capacity experiments indicate that the compound does not exhibit low dimensional magnetism. The results show that no simple antiferromagnetic order can be assumed.
Ungewöhnliche paramagnetische Zentren in Markasitkristallen
Authors: Siebert D. , Dahlem J. , Doll M. 
Published: July 2012

AbstractIn natural single crystals of marcasite we could detect Mn2+ on iron site by EPR in the low‐spin configuration with S = 1/2, and Cu2+ within a compressed ligand octahedron. The unusual EPR parameters are considered to be tue to the strongly covalent bonding. Further resonances were assigned to Au0, presumably also on iron site, (SF)2‐, and S−, alltogether centers with spin S = 1/2.
ESR‐Investigations on the Superionic Behaviour of Doped β‐PbF2
Authors: Ten Eicken J. , Gunsser W. , Chernov S. V. , Murin I. V. 
Published: July 2012

AbstractESR results of low concentrated systems Pb1‐x{Gd,Sc}xF2+x at temperatures up to 775 K are reported. At room temperature, ESR‐spectra of single crystals and polycrystalline samples show three sets of lines which are correlated to different Gd‐sites. The observed shift of the line positions with increasing temperature is caused by the decreasing crystal field interaction. There is no temperature dependence of the differential linewidth until about 600 K. At higher temperatures we observed a drastic increase of the linewidth, correlated to the faster relaxation upon transition to the superionic state.
IR‐ and XRD‐Investigations on Isomorphous Substituted ZSM‐5 Zeolites
Authors: Kosslick H. , Tuan V. A. , Fricke R. , Peuker Ch. 
Published: July 2012

AbstractGe–ZSM‐5 zeolites are characterized by XRD and IR Spectroscopy in the spectral range of lattice and hydroxyl vibrations. XRD data confirm the high crystallinity of hydrothermally synthesized Ge–ZSM‐5 samples. The incorporation of germanium into the ZSM‐5 framework is proven by the increase of the unit cell volume from 5342 Å3 (silicalite I) to 5390 Å3 (Ge–ZSM‐5, Si/Ge = 4). At the same time the wavenumber of the asymmetric T–O–T stretching vibration band is decreased from 1102 to 1090 cm−1 and the intensity of the double ring vibration band at 550 cm−1 is decreased and losses its structure. In the hydroxyl vibration spectra a new absorption band at ca. 3670 cm−1 is observed the intensity of which increases with growing germanium content. This new absorption band is assigned to terminal Ge–OH groups in the zeolite structure.