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EN: In a eutectic mixture of two ionic liquids, we have synthesized and crystallized the new polychloride compound [Et4N]2[(Cl3)2⋅Cl2] that exhibits a periodic 2D polychloride network acting as an anionic layer. Based on its low melting point and vapor pressure, this compound can be described as a room-temperature ionic liquid. The compound was fully characterized by IR and Raman spectroscopy as well as single-crystal X-ray structure determination. The characterization was complemented by solid-state quantum-chemical calculations confirming the results of the experimental work.

DE: Aus einem Eutektikum zweier ionischer Flüssigkeiten wurde das neuartige Polychlorid [Et4N]2[(Cl3)2⋅Cl2] kristallisiert, welches eine anionische Schichtstruktur aus einem 2D-Polychloridnetzwerk besitzt. Aufgrund ihres niedrigen Schmelzpunkts und Dampfdrucks kann die Verbindung als RTIL (room temperature ionic liquid) beschrieben werden. Die Verbindung wurde mittels IR- und Raman-Spektroskopie sowie Einkristall-Röntgenstrukturanalyse vollständig charakterisiert. Quantenchemische Festkörperberechnungen bestätigen die experimentellen Ergebnisse und geben weitere Einblicke in die Bindungssituation.

  • I. Barth, C. Daniel, E. Gindensperger, J. Manz, J. F. Pérez-Torres, A. Schild, C. Stemmle, D. Sulzer and Y. Yang: Intramolecular nuclear flux densities, Advances in Multi-Photon Processes and Spectroscopy - Vol. 22, World Scientific Publishing Co. Pte. Ltd, Singapore, 2015. ISBN 978-981-4619-03-5

The topic of this survey article has seen a renaissance during the past couple of years. Here we present and extend the results for various phenomena which we have published from 2012-2014, with gratitude to our coauthors. The new phenomena include (a) the first reduced nuclear flux densities in vibrating diatomic molecules or ions which have been deduced from experimental pump–probe spectra; these "experimental" nuclear flux densities reveal several quantum effects including (b) the "quantum accordion", i.e., during the turn from bond stretch to bond compression, the diatomic system never stands still - instead, various parts of it with different bond lengths slow into opposite directions. (c) Wavepacket interferometry has been extended from nuclear densities to flux densities, again revealing new phenomena: For example, (d) a vibrating nuclear wave function with compact initial shape may split into two partial waves which run into opposite directions, thus causing interfering flux densities. (e) Tunneling in symmetric 1-dimensional double-well systems yields maximum values of the associated nuclear flux density just below the potential barrier; this is in marked contrast with negligible values of the nuclear density just below the barrier. (f) Nuclear flux densities of pseudorotating nuclei may induce huge magnetic fields. A common methodologic theme of all topics is the continuity equation which connects the time derivative of the nuclear density to the divergence of the flux density, subject to the proper boundary conditions. (g) Nearly identical nuclear densities with different boundary conditions may be related to entirely different flux densities, e.g., during tunneling in cyclic versus non-cyclic systems. The original continuity equation, density and flux density of all nuclei, or of all nuclear degrees of freedom, may be reduced to the corresponding quantities for just a single nucleus, or just a single degree of freedom.

  • D. Andrae (editor): Hans Hellmann: Einführung in die Quantenchemie, Springer Spektrum, Berlin, Heidelberg, 2015. ISBN 978-3-662-45967-6

Im Jahr 1937 erschienen die ersten Lehrbücher des damals noch sehr jungen Fachgebiets der Quantenchemie, beide geschrieben von Hans Hellmann (1903-1938). Im Gegensatz zu anderen frühen Werken zu diesem und nah verwandten Fachgebieten, wie den Büchern von Pauling & Wilson (1935) oder von Eyring, Walter & Kimball (1944), wurden Hellmanns Lehrbücher später weder nachgedruckt noch neu aufgelegt. Beachtet man seine bedeutenden wissenschaftlichen Leistungen - erwähnt seien hier die Aufklärung der Natur der kovalenten chemischen Bindung (1933), das molekulare Virialtheorem (1933), das quantenmechanische Krafttheorem (1933, 1936/1937, heute als Hellmann-Feynman-Theorem bekannt), die Pseudopotentialmethode (1934) und die später von Born und Huang erneut und weiter bearbeitete Theorie der diabatischen und adiabatischen Elementarreaktionen (1935) -, so kann dieser Sachverhalt nur unzureichend durch Hellmanns tragisches Schicksal erklärt werden. Eine Neuauflage der deutschen Fassung von Hellmanns Lehrbuch ist daher mehr als wünschenswert.

  • L. Hammerschmidt and B. Paulus: Electronic structure and transport properties of filled CoSb3 skutterudites by first principles, Phys. Status Solidi A, 1–8 (2015). DOI: 10.1002/pssa.201532609

The CoSb3 skutterudite is a promising thermoelectric material with favorable electronic transport properties. Filling of the voids of CoSb3 skutterudites bears the possibility to reduce the thermal conductivity often without deteriorating much the good electronic transport properties. In this work, we present a systematic comparison of YxCo4Sb12 with Y = Ga, In, Tl by first principles. We perform this analysis by computing the lattice structure, the electronic structure and the electronic transport properties and by comparing to experimental values. Our results indicate that while In and Tl occupy the vacant 2a Wyckoff positions, Ga tends to substitute Sb atoms. We show that the gradual filling leads to a gradual n-type doping as well as a gradual change in the shape of the electronic band structure. Most of the change in the electronic structure is due to the increasing lattice parameter. However, for filling fractions that exceed x=0.04 the rigid band structure model becomes increasingly inaccurate. This indicates an additional interaction of the inline image rings with the filling elements. The latter is reflected in the atom projected band structure computations.

  • C. Liu, J. Manz and Y. Yang: Nuclear fluxes during coherent tunnelling in asymmetric double well potentials, J. Phys. B: At. Mol. Opt. Phys. 48, 164001 (2015). DOI: 10.1088/0953-4075/48/16/164001

Previous results for nuclear fluxes during coherent tunnelling of molecules with symmetric double well potentials are extended to fluxes in asymmetric double well potentials. The theory is derived using the two-state approximation (TSA). The symmetric system serves as a reference. As an example, we consider the one-dimensional model of the tunnelling inversion of oriented ammonia, with semiclassical dipole coupling to an electric field. The tunnelling splitting increases with the dipole coupling by a factor f > 1. The tunnelling time decreases by 1/f. The nuclear density appears as the sum of two parts: The tunnelling part decreases as 1/f2 times the density of the symmetric reference, whereas the non-tunnelling part is the initial density times (1-1/f2). Likewise, the nuclear flux decreases by 1/f, with essentially the same shape as for the symmetric reference, with maximum value at the potential barrier. Coherent nuclear tunnellings starting from the upper or lower wells of the asymmetric potential are equivalent. The results are universal, in the frame of the TSA, hence they allow straightforward extrapolations from one system to others. This is demonstrated by the prediction of isotope effects for five isotopomers of ammonia.

  • T. C. Scott and D. Andrae: Quantum nonlocality and conservation of momentum, Phyiscs Essays 28, 374-385 (2015).

Herein, we review a many-body relativistic theory in the context of quantum entanglement and nonlocality. We extract from a collection of charged particles a formulation which obeys (i) particle–particle symmetry, (ii) conservation rules for the total canonical momentum and total energy, (iii) Maxwell’s equations, and (iv) relativistic invariance. An important aspect related to quantum entanglement is the existence and the formulation of a conservation law for total generalized momenta within a relativistic action-at-a-distance framework for such a collection of charged particles. It is thus found that there is more correspondence between some of the older Machian notions of classical mechanics and quantum entanglement than previously realized and it is suggested that the apparent nonlocal effects in quantum mechanics can be explained without having to resort to any violation of causality thanks to a “handshake” principle resulting from Hamilton’s principle applied to a closed system of charged particles as a whole ensemble.

  • E. Fertitta, M. El Khatib, G. L. Bendazzoli, B. Paulus, S. Evangelisti and Thierry Leininger: The spin-partitioned total position-spread tensor: An application to Heisenberg spin chains, J. Chem. Phys. 143, 244308 (2015).DOI: 10.1063/1.4936585

The spin partition of the Total Position-Spread (TPS) tensor has been performed for one-dimensional Heisenberg chains with open boundary conditions. Both the cases of a ferromagnetic (high-spin) and an anti-ferromagnetic (low-spin) ground-state have been considered. In the case of a low-spin ground-state, the use of alternating magnetic couplings allowed to investigate the effect of spin-pairing. The behavior of the spin-partitioned TPS (SP-TPS) tensor as a function of the number of sites turned to be closely related to the presence of an energy gap between the ground-state and the first excited-state at the thermodynamic limit. Indeed, a gapped energy spectrum is associated to a linear growth of the SP-TPS tensor with the number of sites. On the other hand, in gapless situations, the spread presents a faster-than-linear growth, resulting in the divergence of its per-site value. Finally, for the case of a high-spin wave function, an analytical expression of the dependence of the SP-TPS on the number of sites n and the total spin-projection Sz has been derived.

  • M. Berg, B. Paulus and T. Bredtmann: Electronic quantum fluxes in vibrating symmetric and polar single, double and triple bonds, Mol. Phys. (2015).DOI: 10.1080/00268976.2015.1122843

We investigate electronic quantum fluxes during large amplitude nuclear vibrations of hydrocarbon (HnCCHn), hydrosilicon (HnSiSiHn) and organosilicon (HnSiCHn) compounds with n = 1, 2, 3. The total electronic fluxes are analysed in terms of contributions from localised molecular orbital densities. Furthermore, the vibrationally induced charge transfer in the polar compounds is investigated in terms of the underlying fluxes.

  • Z. Kaawar and B. Paulus: A computational study of the structure of zinc fluoride surfaces, AIP Conf. Proc. 1653, 020051 (2015).DOI: 10.1063/1.4914242

First-principle calculations based on density functional theory were used to investigate the stability and the shape of ZnF2 crystals in vacuum. We present and discuss the results of calculations of the ZnF2 bulk and surface structure, in the rutile and CaCl2 modifications. According to our bulk calculations, the rutile and the CaCl2 structures have similar lattice parameters and bulk energy. The surface energies calculated for the two structures show some differences, but the relative stability of the surfaces stays the same for both structures.

  • D. Trawny, P. Schlexer, K. Steenbergen, J. P. Rabe, B. Paulus and H. U. Reissig: Dense or Porous Packing? Two-Dimensional Self-Assembly of Star-Shaped Mono-, Bi-, and Terpyridine Derivatives, Chem. Phys. Chem. 16, 949-953 (2015).DOI: 10.1002/cphc.201402900

The self-assembly behavior of five star-shaped pyridyl-functionalized 1,3,5-triethynylbenzenes was studied at the interface between an organic solvent and the basal plane of graphite by scanning tunneling microscopy. The mono- and bipyridine derivatives self-assemble in closely packed 2D crystals, whereas the derivative with the more bulky terpyridines crystallizes with porous packing. DFT calculations of a monopyridine derivative on graphene, support the proposed molecular model. The calculations also reveal the formation of hydrogen bonds between the nitrogen atoms and a hydrogen atom of the neighboring central unit, as a small nonzero tunneling current was calculated within this region. The title compounds provide a versatile model system to investigate the role of multivalent steric interactions and hydrogen bonding in molecular monolayers.

  • T. Gomez, G. Hermann, X. Zarate, J. F. Pérez-Torres and J. C. Tremblay: Imaging the Ultrafast Photoelectron Transfer Process in Alizarin-TiO2, Molecules 20, 13830-13853 (2015).DOI: 10.3390/molecules200813830

In this work, we adopt a quantum mechanical approach based on time-dependent density functional theory (TDDFT) to study the optical and electronic properties of alizarin supported on TiO2 nano-crystallites, as a prototypical dye-sensitized solar cell. To ensure proper alignment of the donor (alizarin) and acceptor (TiO2 nano-crystallite) levels, static optical excitation spectra are simulated using time-dependent density functional theory in response. The ultrafast photoelectron transfer from the dye to the cluster is simulated using an explicitly time-dependent, one-electron TDDFT ansatz. The model considers the δ-pulse excitation of a single active electron localized in the dye to the complete set of energetically accessible, delocalized molecular orbitals of the dye/nano-crystallite complex. A set of quantum mechanical tools derived from the transition electronic flux density is introduced to visualize and analyze the process in real time. The evolution of the created wave packet subject to absorbing boundary conditions at the borders of the cluster reveal that, while the electrons of the aromatic rings of alizarin are heavily involved in an ultrafast charge redistribution between the carbonyl groups of the dye molecule, they do not contribute positively to the electron injection and, overall, they delay the process.

  • T. Bredtmann, D. J. Diestler, S.-D. Li, J. Manz, J. F. Pérez-Torres, W.-J. Tian, Y.-B. Wu, Y. Yang and H.-J. Zhai: Quantum theory of concerted electronic and nuclear fluxes associated with adiabatic intramolecular processes, Phys. Chem. Chem. Phys. 17, 29421-29464 (2015).DOI: 10.1039/C5CP03982G

An elementary molecular process can be characterized by the flow of particles (i.e., electrons and nuclei) that compose the system. The flow, in turn, is quantitatively described by the flux (i.e., the time-sequence of maps of the rate of flow of particles though specified surfaces of observation) or, in more detail, by the flux density. The quantum theory of concerted electronic and nuclear fluxes (CENFs) associated with electronically adiabatic intramolecular processes is presented. In particular, it is emphasized how the electronic continuity equation can be employed to circumvent the failure of the Born–Oppenheimer approximation, which always predicts a vanishing electronic flux density (EFD). It is also shown that all CENFs accompanying coherent tunnelling between equivalent “reactant” and “product” configurations of isolated molecules are synchronous. The theory is applied to three systems of increasing complexity. The first application is to vibrating, aligned H2+(2Σg+), or vibrating and dissociating H2+(2Σg+, J = 0, M = 0). The EFD maps manifest a rich and surprising structure in this simplest of systems; for example, they show that the EFD is not necessarily synchronous with the nuclear flux density and can alternate in direction several times over the length of the molecule. The second application is to coherent tunnelling isomerization in the model inorganic system B4, in which all CENFs are synchronous. The contributions of core and valence electrons to the EFD are separately computed and it is found that core electrons flow with the nuclei, whereas the valence electrons flow obliquely to the core electrons in distinctive patterns. The third application is to the Cope rearrangement of semibullvalene, which also involves coherent tunnelling. An especially interesting discovery is that the so-called “pericyclic” electrons do not behave in the manner typically portrayed by the traditional Lewis structures with appended arrows. Indeed, it is found that only about 3 pericyclic electrons flow, in contrast to the 6 predicted by the Lewis picture. It is remarkable that the time scales of these three processes vary by 18 orders of magnitude: femtoseconds (H2+(2Σg+)); picoseconds (B4); kilosceconds (semibullvalene). It is emphasized that results presented herein are appearing in the literature for the first time.

  • E. Fertitta, B. Paulus, G. Barcza, Ö. Legeza: On the calculation of complete dissociation curves of closed-shell pseudo-onedimensional systems via the complete active space method of increments, J. Chem. Phys. 143, 114108 (2015).DOI: 10.1063/1.4930861

The method of increments (MoI) has been employed using the complete active space formalism in order to calculate the dissociation curve of beryllium ring-shaped clusters Be n of different sizes. Benchmarks obtained through different quantum chemical methods including the ab initio density matrix renormalization group were used to verify the validity of the MoI truncation which showed a reliable behavior for the whole dissociation curve. Moreover we investigated the size dependence of the correlation energy at different interatomic distances in order to extrapolate the values for the periodic chain and to discuss the transition from a metal-like to an insulator-like behavior of the wave function through quantum chemical considerations.

  • E. Kanaki, G. Sansone, L. Maschio, B. Paulus: The effect of electron correlation on the adsorption of hydrogen fluoride and water on magnesium fluoride surfaces , Phys. Chem. Chem. Phys. 17, 18722-18728 (2015).DOI: 10.1039/C5CP02017D

We have performed periodic density functional and periodic local MP2 calculations for the adsorption of hydrogen fluoride and water on the four low index surfaces (001), (100), (101) and (110) of magnesium fluoride. While the adsorption of HF is described well using B3LYP, MP2 is required for a good description of the adsorption of H2O. Post-optimization dispersion corrections of B3LYP are found to consistently overestimate the adsorption energy. The coordination of surface cations, the presence of hydroxyls on the surface, as well as the coverage appear to play an equally important role in the adsorption.

  • E. Kanaki, S. Gohr, C. Müller, B. Paulus: Theoretical study on the morphology of MgF2 nanocrystals at finite temperature and pressure, Surf. Sci. 632, 158-163 (2015).DOI: 10.1016/j.susc.2014.10.007

Periodic density functional theory and surface thermodynamics were combined in a model for the relative stability of rutile-structured MgF2 surfaces in a mixed H2O/HF gas phase. We performed DFT calculations for surfaces (001), (100), (101) and (110), considering H2O and HF adsorption, as well as hydroxylation of the surfaces. The influence of temperature and composition of the gas phase on the surface energies was explored using ab-initio thermodynamics. We found that the relative stability of the surfaces, which depends on their composition, is governed by the thermodynamic equilibrium between gas phase and solid. As a consequence, the morphology of the crystallites strongly varies depending on these parameters.

  • D. Trawny, M. Quennet, N. Rades, D. Lentz, B. Paulus, H. U. Reissig: Syntheses, Structures and Conformational Dynamics of 1,3,5-Tris-(3"-ethynylbiphenyl-2'-yl)benzene Derivatives, Eur. J. O. C. 21, 4667–4674 (2015).DOI: 10.1002/ejoc.201500615

Following a route described by Müllen et al. we improved the preparation of 1,2,3-tris(3″-iodobiphenyl-2′-yl)benzene (4). During the required iododesilylation with iodine monochloride the unexpected formation of a mono-chlorinated compound 6 as major product was observed, when an excess of the iodination reagent was employed. The reaction mechanism for the formation of this compound involving an oxidizing process is discussed. X-ray crystallography of the subsequent alkynylated product 7 proves the location of the chlorine atom at the central benzene ring. The related compound 5 was likewise investigated by X-ray analysis revealing a preferred solid-state conformation (“2-up-1-down”) different from that of the chlorinated compound (“propeller” conformation). Compound 7 showed remarkable conformational dynamics in solution as observed by 1H NMR spectroscopy. Temperature-dependent measurements allowed the calculation of an energy difference of two major conformers of ca. 2 kJ/mol and a rotational barrier ΔGrot of ca. 77 kJ/mol. These values were convincingly confirmed by DFT calculations. A subsequent Sonogashira reaction of 4 with a suitable bipyridine derivative provided a unique trivalent bipyridine derivative.

  • L. E. Marsoner Steinkasserer, B. Paulus, N. Gaston: Hybrid density functional calculations of the surface electronic structure of GdN, Phys. Rev. B 91, 235148 (2015).DOI: 10.1103/PhysRevB.91.235148

Rare-earth nitrides are a promising class of materials for application in spintronics, with GdN a particularly well-studied example. Here we perform band-structure calculations employing a hybrid density functional, which enables the band gap to be more accurately predicted through the inclusion of short-range exact exchange. The sensitivity of the band gap to the exchange term is demonstrated. The surface electronic structure is simulated through the use of slab models of the GdN(111) surface, which provide a consistent description of metallic surface states in the majority-spin channel.

  • T. Vent-Schmidt, F. Brosi, J. Metzger, T. Schlöder, X. Wang, L. Andrews, C. Müller, H. Beckers, S. Riedel : Fluorine Rich Fluorides: New Insights into the Chemistry of Polyfluoride Anions, Angew. Chem. Int. Ed. 2015.DOI: 10.1002/anie.201502624 - Angew. Chem. 2015.DOI: 10.1002/ange.201502624

EN: Polyfluoride anions have been investigated by matrix-isolation spectroscopy and quantum-chemical methods. For the first time the higher polyfluoride anion [F5]-; has been observed under cryogenic conditions in neon matrices at 850 cm-1. In addition, a new band for the Cs+[F3]- complex in neon is reported.

DE: Polyfluoride wurden mittels Matrixisolationsspektroskopie und quantenchemischen Berechnungen auf Coupled-Cluster-Niveau untersucht. Erstmalig konnte ein höheres Polyfluoridanion spektroskopisch in Neonmatrices bei 4 K nachgewiesen werden. Das C2v-symmetrische [F5]- weist eine sehr starke Bande bei 850 cm-1 auf. Darüber hinaus wird eine neue Bande für den Cs+[F3]--Komplex in Neon beschrieben.

  • C. Müller, D. Spångberg: Calculation of the stability of nonperiodic solids using classical force fields and the method of increments: N2O as an example, J. Comp. Chem. 36(18), 1420 (2015).DOI: 10.1002/jcc.23939

Combining classical force fields for the Hartree–Fock (HF) part and the method of increments for post-HF contributions, we calculate the cohesive energy of the ordered and randomly disordered nitrous oxide (N2O) solid. At 0 K, ordered N2O is most favorable with a cohesive energy of −27.7 kJ/mol. At temperatures above 60 K, more disordered structures become compatible and a phase transition to completely disordered N2O is predicted. Comparison with experiment in literature suggests that experimentally prepared N2O crystals are mainly disordered due to a prohibitively high activation energy of ordering processes.

  • L. Hammerschmidt, M. Quennet, K. Töpfer, B. Paulus: Low-index surfaces of CoSb3 skutterudites from first principles, Surf. Sci. 637-638, 1-158 (2015).DOI: 10.1016/j.susc.2015.03.020

We have performed first-principles calculations for all the differently terminated three low-index surfaces of CoSb3 skutterudite. Surface energies, lattice structures and electronic structures have been investigated applying different functionals within the plane-wave density functional theory. Each functional consistently reveals the (110) as the most stable surface, followed by (100) and (111), respectively. For each surface plane we have studied all possible terminating surface layers and a structural comparison shows that the surface stability is mostly determined by the Sb4 subunits. Wherever complete Sb4 subunits remain intact at the surface the stability is high. For the most stable surfaces, we have calculated the surface band structure in reference to the projected bulk band continuum and identified surface states. These surface states promote the metallic character at the CoSb3 surfaces. The freedom of spin polarization leads to a magnetic configuration in the (110) case.

  • M. Lohse, K. Nowosinski, N. L. Traulsen, A. J. Achazi, L. K. S. von Krbek, B. Paulus, C. A. Schalley, S. Hecht: Gating the photochromism of an azobenzene by strong host–guest interactions in a divalent pseudo[2]rotaxane, Chem. Commun. 51, 9777-9780 (2015).DOI: 10.1039/C5cc02811F

The ability of an E-configured azobenzene guest to undergo photoisomerisation is controlled by the presence of a complementary host. Addition of base/acid allowed for a weakening/strengthening of the interactions in the divalent pseudo[2]rotaxane complex and hence could switch on/off photochromic activity.

  • A. J. Achazi, D. Mollenhauer, B. Paulus: First principle investigation of the linker length effects on the thermodynamics of divalent pseudorotaxanes, Beilstein J. Org. Chem 11, 687-692 (2015).DOI: 10.3762/bjoc.11.78

The Gibbs energies of association (Gibbs free (binding) energies) for divalent crown-8/ammonium pseudorotaxanes are determined by investigating the influence of different linkers onto the binding. Calculations are performed with density functional theory including dispersion corrections. The translational, rotational and vibrational contributions are taken into account and solvation effects including counter ions are investigated by applying the COSMO-RS method, which is based on a continuum solvation model. The calculated energies agree well with the experimentally determined ones. The shortest investigated linker shows an enhanced binding strength due to electronic effects, namely the dispersion interaction between the linkers from the guest and the host. For the longer linkers this ideal packing is not possible due to steric hindrance.

  • J. Manz, K. Sato, T. Takayanagi, T. Yoshida: From photoelectron detachment spectra of BrHBr, BrDBr and IHI, IDI to vibrational bonding of BrMuBr and IMuI, J. Chem. Phys. 142, 164308 (2015).DOI: 10.1063/1.4918980

Photoelectron detachment XLX(0000) + hν → XLX(vib) + e + KER (X = Br or I, L = H or D) at sufficiently low temperatures photoionizes linear dihalogen anions XLX in the vibrational ground state (v1v2lv3 = 0000) and prepares the neutral radicals XLX(vib) in vibrational states (vib). At the same time, part of the photon energy (hν) is converted into kinetic energy release (KER) of the electron [R. B. Metz, S. E. Bradforth, and D. M. Neumark, Adv. Chem. Phys. 81, 1 (1992)]. The process may be described approximately in terms of a Franck-Condon type transfer of the vibrational wavefunction representing XLX(0000) from the domain close to the minimum of its potential energy surface (PES) to the domain close to the linear transition state of the PES of the neutral XLX. As a consequence, prominent peaks of the photoelectron detachment spectra (pds) correlate with the vibrational energies EXLX,vib of states XLX(vib) which are centered at linear transition state. The corresponding vibrational quantum numbers may be labeled vib = (v1v2lv3) = (000v3). Accordingly, the related most prominent peaks in the pds are labeled v3. We construct a model PES which mimics the “true” PES in the domain of transition state such that it supports vibrational states with energies EXLX,pds,000v3 close to the peaks of the pds labeled v3 = 0, 2, and 4. Subsequently, the same model PES is also used to calculate approximate values of the energies EXMuX,0000 of the isotopomers XMuX(0000). For the heavy isotopomers XHX and XDX, it turns out that all energies EXLX,000v3 are above the threshold for dissociation, which means that all heavy XLX(000v3) with wavefunctions centered at the transition state are unstable resonances with finite lifetimes. Turning the table, bound states of the heavy XLX are van der Waals (vdW) bonded. In contrast, the energies EXMuX,0000 of the light isotopomers XMuX(0000) are below the threshold for dissociation, with wavefunctions centered at the transition state. This means that XMuX(0000) are vibrationally bonded. This implies a fundamental change of the nature of chemical bonding, from vdW bonding of the heavy XHX, XDX to vibrational bonding of XMuX. For BrMuBr, the present results derived from experimental pds of BrHBr and BrDBr confirm the recent discovery of vibrational bonding based on quantum chemical ab initio calculations [D. G. Fleming, J. Manz, K. Sato, and T. Takayanagi, Angew. Chem., Int. Ed. 53, 13706 (2014)]. The extension from BrLBr to ILI means the discovery of a new example of vibrational bonding. These empirical results for the vibrational bonding of IMuI, derived from the photoelectron spectra of IHI and IDI, are supported by ab initio simulations of the spectra and of the wavefunction representing vibrational bonding of IMuI.

  • L. E. Marsoner Steinkasserer, N. Gaston, B. Paulus: Weak interactions in Graphane/BN systems under static electric fields—A periodic ab-initio study, J. Chem. Phys. 142, 154701 (2015).DOI: 10.1063/1.4917170

Ab-initio calculations via periodic Hartree-Fock (HF) and local second-order Møller-Plesset perturbation theory (LMP2) are used to investigate the adsorption properties of combined Graphane/boron nitride systems and their response to static electric fields. It is shown how the latter can be used to alter both structural as well as electronic properties of these systems.

  • F. Ferraro, J. F. Pérez-Torres, C. Z. Hadad: Selective Catalytic Activation of Acetylene by a Neutral Gold Cluster of Experimentally Known Gas-Phase Geometry, J. Phys. Chem. C, Article ASAP (2015).DOI: 10.1021/jp512989q

The electronic and structural details for the acetylene selective catalytic activation by one of the few small gold clusters whose experimental gas-phase initial geometry in neutral charge state is known, the gold heptamer, are investigated. Doing an exhaustive search of the acetylene–gold heptamer ZORA scalar relativistic PW91/TZ2P configurational space, we determine the main, secondary, and also the unimportant structures relative to the catalytic activation. We found that the leading mechanism of activation consists in the tendency to the disappearance of one of the acetylene π bonds at the expense of the formation of C–Au strong interactions, by the predominant dative interaction of s/d-like gold heptamer molecular orbitals toward a π* orbital of acetylene. This results in adducts having very diminished energy barriers toward processes such as, for example, the selective hydrogenation reaction to ethylene. This activation would occur with a considerable change of the participant species geometries and, with the formation of a frontier single occupied molecular orbital, very localized at carbon atoms region.

  • J. F. Pérez-Torres: Dissociating H2+(2Σg+,JM=00) Ion as an Exploding Quantum Bubble, J. Phys. Chem. A 119, 2895–2901 (2015).DOI: 10.1021/acs.jpca.5b00907

The nuclear and electronic probability and flux densities for a vibrating and dissociating H2+ molecular ion in the electronic and rotational ground state (corresponding to the quantum numbers 2Σg+,JM = 00) are calculated. As a consequence of the isotropy of the scenario, the vibrating H2+ appears as a pulsating quantum bubble, while the dissociating H2+ appears as an exploding quantum bubble. The dissociating part is represented by a discretization of the continuum through use of integrable B-spline basis set. It is shown that the vibrating part (the pulsating quantum bubble) interferes with the dissociating part (the exploding quantum bubble) and that the interference is much more noticeable in the probability density than in the flux density.

  • M. El Khatib, O. Brea, E. Fertitta, G. L. Bendazzoli, S. Evangelisti, T. Leininger: The total position-spread tensor: spin partition, J. Chem. Phys. 142, 094113 (2015).DOI: 10.1063/1.4913734

The Total Position Spread (TPS) tensor, defined as the second moment cumulant of the position operator, is a key quantity to describe the mobility of electrons in a molecule or an extended system. In the present investigation, the partition of the TPS tensor according to spin variables is derived and discussed. It is shown that, while the spin-summed TPS gives information on charge mobility,the spin-partitioned TPS tensor becomes a powerful tool that provides information about spin fluctuations. The case of the hydrogen molecule is treated, both analytically, by using a 1s Slater-type orbital, and numerically, at Full Configuration Interaction (FCI) level with a V6Z basis set. It is found that, for very large inter-nuclear distances, the partitioned tensor growths quadratically with the distance in some of the low-lying electronic states. This fact is related to the presence of entanglement in the wave function. Non-dimerized open chains described by a model Hubbard Hamiltonian and linear hydrogen chains Hn (n≥2), composed of equally spaced atoms, are also studied at FCI level. The hydrogen systems show the presence of marked maxima for the spin-summed TPS (corresponding to a high charge mobility) when the inter-nuclear distance is about 2 bohrs. This fact can be associated to the presence of a Mott transition occurring in this region. The spin-partitioned TPS tensor, on the other hand, has a quadratical growth at long distances, a fact that corresponds to the high spin mobility in a magnetic system.

  • M. El Khatib, O. Brea, E. Fertitta, G. L. Bendazzoli, S. Evangelisti, T. Leininger, B. Paulus: Spin delocalization in hydrogen chains described with the spin-partitioned total position-spread tensor, Theor. Chem. Acc. 134, 29 (2015).DOI: 10.1007/s00214-015-1625-7

The formalism of the spin-partitioned total position spread (SP-TPS) tensor is applied to model systems treated at ab initio level. They are hydrogen linear chains having different geometries and showing qualitatively different behaviors. Indeed, the SP-TPS behavior depends in a crucial way on the entanglement properties of the chain wave function. It is shown that the SP-TPS tensor gives a measure of the spin delocalization in the chain. This is very low in the case of isolated fixed-length dimers and maximal for chains of equally spaced atoms. The present formalism could be used to describe, for instance, the spin fluctuation associated with spintronic devices.

  • K. G. Steenbergen, N. Gaston: Quantum Size Effects in the Size-Temperature Phase Diagram of Gallium: Structural Characterization of Shape-Shifting Clusters, Chem. Eur. J. 21, 2862-2869 (2015).DOI: 10.1002/chem.201405718

Finite temperature analysis of cluster structures is used to identify signatures of the low-temperature polymorphs of gallium, based on the results of first-principle Born–Oppenheimer molecular dynamics simulations. Pre-melting structural transitions proceed from either the β- and/or the δ-phase to the γ- or δ-phase, with a size- dependent phase progression. We relate the stability of each isomer to the electronic structures of the different phases, giving new insight into the origin of polymorphism in this complicated element.

  • J. F. Pérez-Torres: Fourier analysis of the nuclear flux density in diatomic molecules: A complementary tool to map potential-energy curves and to characterize vibrational wave functions, Phys. Rev. A 91, 022510 (2015).DOI: 10.1103/PhysRevA.91.022510

Pump-probe spectroscopy has allowed the construction of the nuclear probability density ρ(R,t) as a function of the internuclear bond distance (R) and the time (t) in diatomic molecules and consequent deduction of the nuclear flux density j(R,t). Thus, the two observables [ρ(R,t),j(R,t)] comprise a very detailed description of the nuclear motion in ultrafast molecular dynamics. Here a Fourier analysis of j(R,t) is proposed and compared with the already existing Fourier analysis of ρ(R,t). It is shown that the two power spectra ∣∣ρ˜(R,ω;T)∣∣2 and ∣∣j˜(R,ω;T)∣∣2 provide the same information in the frequency domain ω, but entirely different information in the spatial domain (i.e., along the R coordinate).

  • C. Liu, J. Manz, Y. Yang: Laser Sculpting of Atomic sp, sp2, and sp3 Hybrid Orbitals, Chem. Phys. Chem. 16, 191 (2015).DOI: 10.1002/cphc.201402588

Atomic sp, sp2, and sp3 hybrid orbitals were introduced by Linus Pauling to explain the nature of the chemical bond. Quantum dynamics simulations show that they can be sculpted by means of a selective series of coherent laser pulses, starting from the 1s orbital of the hydrogen atom. Laser hybridization generates atoms with state-selective electric dipoles, opening up new possibilities for the study of chemical reaction dynamics and heterogeneous catalysis.

  • M. V. Daniel, L. Hammerschmidt, C. Schmidt, F. Timmermann, J. Franke, N. Jöhrmann, M. Hietschold, D. C. Johnson, B. Paulus, and M. Albrecht: Structural and thermoelectric properties of FeSb3 skutterudite thin films, Phys. Rev. B 91, 085410 (2015).DOI: 10.1103/PhysRevB.91.085410

Skutterudites are promising materials for future thermoelectric applications. Whereas the skutterudite CoSb3 is intensively studied, very few investigations for FeSb3 are performed due to its metastable character and the comparably low decomposition temperature. In this work, single-phase FeSb3 thin films were prepared by codeposition of Fe and Sb using molecular beam epitaxy at room temperature followed by postannealing. The transport properties of a Fe-Sb composition series were determined and reveal high power factors S2σ up to 14μW/K2cm. Furthermore, the structural parameters, the electronic structure, and the transport parameters were calculated by density functional theory, giving excellent agreement with the experimental data.

  • L. Hammerschmidt, L. Maschio, C. Müller, B. Paulus: Electron Correlation at the MgF2(110) Surface: A Comparison of Incremental and Local Correlation Methods, J. Chem. Theory Comput. 11, 252–259 (2015).DOI: 10.1021/ct500841b

We have applied the Method of Increments and the periodic Local-MP2 approach to the study of the (110) surface of magnesium fluoride, a system of significant interest in heterogeneous catalysis. After careful assessment of the approximations inherent in both methods, the two schemes, though conceptually different, are shown to yield nearly identical results. This remains true even when analyzed in fine detail through partition of the individual contribution to the total energy. This kind of partitioning also provides thorough insight into the electron correlation effects underlying the surface formation process, which are discussed in detail.

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