研究者詳細 - JESCHKE HARALD OLAF

論文 - JESCHKE HARALD OLAF

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Barlowite as a canted antiferromagnet: Theory and experiment 査読

Harald O. Jeschke, Francesc Salvat-Pujol, Elena Gati, Nguyen Hieu Hoang, Bernd Wolf, Michael Lang, John A. Schlueter, Roser Valenti

PHYSICAL REVIEW B 92 ( 9 ) 2015年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

We investigate the structural, electronic, and magnetic properties of the newly synthesized mineral barlowite Cu-4(OH)(6)FBr which contains Cu2+ ions in a perfect kagome arrangement. In contrast to the spin-liquid candidate herbertsmithite ZnCu3(OH)(6)Cl-2, kagome layers in barlowite are perfectly aligned due to the different bonding environments adopted by F- and Br- compared to Cl-. With the synthesis of this material we unveil a design strategy for layered kagome systems with possible exotic magnetic states. Density functional theory calculations and effective model considerations for Cu-4(OH)(6)FBr, which has a Cu2+ site coupling the kagome layers, predict a three-dimensional network of exchange couplings, which together with a substantial Dzyaloshinskii-Moriya coupling lead to canted antiferromagnetic ordering of this compound in excellent agreement with magnetic susceptibility measurements on single crystals yielding T-N = 15 K.

DOI： 10.1103/PhysRevB.92.094417

Influence of molecular conformations on the electronic structure of organic charge transfer salts 査読

Daniel Guterding, Roser Valenti, Harald O. Jeschke

PHYSICAL REVIEW B 92 ( 8 ) 2015年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

We report ab initio calculations for the electronic structure of organic charge transfer salts kappa-(ET)(2)Cu[N(CN)(2)]Br, kappa-(ET)(2)Cu[N(CN)(2)]I, kappa ''-(ET)(2)Cu[N(CN)(2)]Cl, and kappa-(ET)(2)Cu-2(CN)(3). These materials show an ordering of the relative orientation of terminal ethylene groups in the bis-ethylenedithio-tetrathiafulvalene molecules at finite temperature and our calculations correctly predict the experimentally observed ground state molecular conformations (eclipsed or staggered). Further, it was recently demonstrated that the ethylene end group relative orientations can be used to reversibly tune kappa-(ET)(2)Cu[N(CN)(2)]Br through a metal-insulator transition. Using a tight-binding analysis, we show that the molecular conformations of ethylene end groups are intimately connected to the electronic structure and significantly influence hopping and Hubbard repulsion parameters. Our results place kappa-(ET)(2)Cu[N(CN)(2)]Br in eclipsed and staggered configurations on opposite sides of the metal-insulator transition.

DOI： 10.1103/PhysRevB.92.081109

Role of layer packing for the electronic properties of the organic superconductor (BEDT-TTF)(2)Ag(CF3)(4)(TCE) 査読

Michaela Altmeyer, Roser Valenti, Harald O. Jeschke

PHYSICAL REVIEW B 91 ( 24 ) 2015年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

The charge-transfer compound (BEDT-TTF)(2)Ag(CF3)(4)(TCE) crystallizes in three polymorphs with different alternating layers: While a phase with a kappa packing motif has a low superconducting transition temperature of T-c = 2.6 K, two phases with higher T-c of 9.5 and 11 K are multilayered structures consisting of alpha' and kappa layers. We investigate these three systems within density functional theory and find that the alpha' layer shows different degrees of charge order for the two kappa-alpha' systems and directly influences the electronic behavior of the conducting. layer. We discuss the origin of the distinct behavior of the three polymorphs and propose a minimal tight-binding Hamiltonian for the description of these systems based on projective molecular Wannier functions.

DOI： 10.1103/PhysRevB.91.245137

Origin of the superconducting state in the collapsed tetragonal phase of KFe2As2 査読

Daniel Guterding, Steffen Backes, Harald O. Jeschke, Roser Valenti

PHYSICAL REVIEW B 91 ( 14 ) 2015年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

Recently, KFe2As2 was shown to exhibit a structural phase transition from a tetragonal to a collapsed tetragonal phase under an applied pressure of about 15 GPa. Surprisingly, the collapsed tetragonal phase hosts a superconducting state with T-c similar to 12 K, while the tetragonal phase is a T-c <= 3.4 K superconductor. We show that the key difference between the previously known nonsuperconducting collapsed tetragonal phase in AFe(2)As(2) (A = Ba, Ca, Eu, Sr) and the superconducting collapsed tetragonal phase in KFe2As2 is the qualitatively distinct electronic structure. While the collapsed phase in the former compounds features only electron pockets at the Brillouin zone boundary and no hole pockets are present in the Brillouin zone center, the collapsed phase in KFe2As2 has almost nested electron and hole pockets. Within a random phase approximation spin fluctuation approach we calculate the superconducting order parameter in the collapsed tetragonal phase. We propose that a Lifshitz transition associated with the structural collapse changes the pairing symmetry from d wave (tetragonal) to s(+/-) (collapsed tetragonal). Our density functional theory combined with dynamical mean-field theory calculations show that effects of correlations on the electronic structure of the collapsed tetragonal phase are minimal. Finally, we argue that our results are compatible with a change of sign of the Hall coefficient with pressure, as observed experimentally.

DOI： 10.1103/PhysRevB.91.140503

Analysis of the optical conductivity for A(2)IrO(3) (A = Na, Li) from first principles 査読

Ying Li, Kateryna Foyevtsova, Harald O. Jeschke, Roser Valenti

PHYSICAL REVIEW B 91 ( 16 ) 2015年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

We present results for the optical conductivity of Na2IrO3 within density functional theory by including spin-orbit and correlation effects as implemented in the generalized gradient approximation. We identify the various interband transitions and show that the underlying quasimolecular-orbital nature of the electronic structure in Na2IrO3 translates into distinct features in the optical conductivity. Most importantly, the parity of the quasimolecular orbitals appears to be the main factor in determining strong and weak optical transitions. We also present optical conductivity calculations for alpha-Li2IrO3 and discuss the similarities and differences with Na2IrO3.

DOI： 10.1103/PhysRevB.91.161101

Effects of Lifshitz Transition on Charge Transport in Magnetic Phases of Fe-Based Superconductors 査読

Y. Wang, Maria N. Gastiasoro, Brian M. Andersen, M. Tomic, Harald O. Jeschke, Roser Valenti, Indranil Paul, P. J. Hirschfeld

PHYSICAL REVIEW LETTERS 114 ( 9 ) 2015年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

The unusual temperature dependence of the resistivity and its in-plane anisotropy observed in the Fe-based superconducting materials, particularly Ba(Fe1-xCox)(2)As-2, has been a long-standing puzzle. Here, we consider the effect of impurity scattering on the temperature dependence of the average resistivity within a simple two-band model of a dirty spin density wave metal. The sharp drop in resistivity below the Neel temperature T-N in the parent compound can only be understood in terms of a Lifshitz transition following Fermi surface reconstruction upon magnetic ordering. We show that the observed resistivity anisotropy in this phase, arising from nematic defect structures, is affected by the Lifshitz transition as well.

DOI： 10.1103/PhysRevLett.114.097003

Localized versus itinerant states created by multiple oxygen vacancies in SrTiO3 査読

Harald O. Jeschke, Juan Shen, Roser Valenti

NEW JOURNAL OF PHYSICS 17 2015年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

Oxygen vacancies in strontium titanate surfaces (SrTiO3) have been linked to the presence of a two-dimensional electron gas with unique behavior. We perform a detailed density functional theory study of the lattice and electronic structure of SrTiO3 slabs with multiple oxygen vacancies, with a main focus on two vacancies near a titanium dioxide terminated SrTiO3 surface. We conclude based on total energies that the two vacancies preferably inhabit the first two layers, i.e. they cluster vertically, while in the direction parallel to the surface, the vacancies show a weak tendency towards equal spacing. Analysis of the nonmagnetic electronic structure indicates that oxygen defects in the surface TiO2 layer lead to population of Tit(2g) states and thus itinerancy of the electrons donated by the oxygen vacancy. In contrast, electrons from subsurface oxygen vacancies populate Ti e(g) states and remain localized on the two Ti ions neighboring the vacancy. We find that both the formation of a bound oxygen-vacancy state composed of hybridized Ti 3e(g) and 4p states neighboring the oxygen vacancy as well as the elastic deformation after extracting oxygen contribute to the stabilization of the in-gap state.

DOI： 10.1088/1367-2630/17/2/023034

Unified picture of the doping dependence of superconducting transition temperatures in alkali metal/ammonia intercalated FeSe 査読

Daniel Guterding, Harald O. Jeschke, P. J. Hirschfeld, Roser Valenti

PHYSICAL REVIEW B 91 ( 4 ) 2015年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

In the recently synthesized Li-x(NH2)(y)(NH3)(z)Fe2Se2 family of iron chalcogenides, a molecular spacer consisting of lithium ions, lithium amide, and ammonia separates the layers of FeSe. It has been shown that upon variation of the chemical composition of the spacer layer, superconducting transition temperatures can reach T-c similar to 44 K, but the relative importance of the layer separation and effective doping to the T-c enhancement is currently unclear. Using state of the art band structure unfolding techniques, we construct eight-orbital models from ab initio density functional theory calculations for these materials. Within an RPA spin-fluctuation approach, we show that the electron doping enhances the superconducting pairing, which is of s(+/-) symmetry and explain the experimentally observed limit to T-c in the molecular spacer intercalated FeSe class of materials.

DOI： 10.1103/PhysRevB.91.041112

Role of layer packing for the electronic properties of the organic superconductor (BEDT-TTF)2Ag(CF3)4(TCE)

Altmeyer, M., Valentí, R., Jeschke, H.O.

Physical Review B - Condensed Matter and Materials Physics 91 ( 24 ) 2015年

Microscopic nature of correlations in multiorbital AFe2As2 (A=K,Rb,Cs): Hund's coupling versus Coulomb repulsion

Backes, S., Jeschke, H.O., Valentí, R.

Physical Review B - Condensed Matter and Materials Physics 92 ( 19 ) 2015年

Charge transfer tuning by chemical substitution and uniaxial pressure in the organic complex tetramethoxypyrene-tetracyanoquinodimethane 査読

Milan Rudloff, Kai Ackermann, Michael Huth, Harald O. Jeschke, Milan Tomic, Roser Valenti, Benedikt Wolfram, Martin Broering, Michael Bolte, Dennis Chercka, Martin Baumgarten, Klaus Muellen

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 17 ( 6 ) 4118 - 4126 2015年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

In the search for novel organic charge transfer salts with variable degrees of charge transfer we have studied the effects of two modifications of the recently synthesized donor-acceptor system [tetra-methoxypyrene (TMP)]-[tetracyanoquinodimethane (TCNQ)]. One is of chemical nature by substituting the acceptor TCNQ molecules by F(4)TCNQ molecules. The second consists in simulating the application of uniaxial pressure along the stacking axis of the system. In order to test the chemical substitution, we have grown single crystals of the TMP-F(4)TCNQ complex and analyzed its electronic structure via electronic transport measurements, ab initio density functional theory (DFT) calculations and UV/VIS/IR absorption spectroscopy. This system shows an almost ideal geometrical overlap of nearly planar molecules stacked alternately (mixed stack) and this arrangement is echoed by a semiconductor-like transport behavior with an increased conductivity along the stacking direction. This is in contrast to TMP-TCNQ which shows a less pronounced anisotropy and a smaller conductivity response. Our band structure calculations confirm the one-dimensional behavior of TMP-F(4)TCNQ with pronounced dispersion only along the stacking axis. Infrared measurements illustrating the C N vibration frequency shift in F(4)TCNQ suggest however no improvement in the degree of charge transfer in TMP-F(4)TCNQ with respect to TMP-TCNQ. In both complexes about 0.1e is transferred from TMP to the acceptor. Concerning the pressure effect, our DFT calculations on the designed TMP-TCNQ and TMP-F(4)TCNQ structures under different pressure conditions show that application of uniaxial pressure along the stacking axis of TMP-TCNQ may be the route to follow in order to obtain a much more pronounced charge transfer.

DOI： 10.1039/c4cp04461d

Unfolding of electronic structure through induced representations of space groups: Application to Fe-based superconductors 査読

Milan Tomic, Harald O. Jeschke, Roser Valenti

PHYSICAL REVIEW B 90 ( 19 ) 2014年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

We revisit the problem that relevant parts of band structures for a given cell choice can reflect exact or approximate higher symmetries of subsystems in the cell and can therefore be significantly simplified by an unfolding procedure that recovers the higher symmetry. We show that band-structure unfolding can be understood as projection onto induced irreducible representations of a group obtained by extending the original group of translations with a number of additional symmetry operations. The resulting framework allows us to define a generalized unfolding procedure that includes the point group operations and can be applied to any quantity in the reciprocal space. The unfolding of the Brillouin zone follows naturally from the properties of the induced irreducible representations. In this context, we also introduce a procedure to derive tight-binding models of reduced dimensionality by making use of point group symmetries. Further, we show that careful consideration of unfolding has important consequences on the interpretation of angle-resolved photoemission experiments. Finally, we apply the unfolding procedure to various representative examples of Fe-based superconductor compounds and show that the one-iron picture arises as an irreducible representation of the glide-reflection group, and we comment on the consequences for the interpretation of one-iron versus two-iron Brillouin zone representations.

DOI： 10.1103/PhysRevB.90.195121

Evidence of a field-induced Berezinskii-Kosterlitz-Thouless scenario in a two-dimensional spin-dimer system 査読

U. Tutsch, B. Wolf, S. Wessel, L. Postulka, Y. Tsui, H. O. Jeschke, I. Opahle, T. Saha-Dasgupta, R. Valenti, A. Bruehl, K. Removic-Langer, T. Kretz, H. -W. Lerner, M. Wagner, M. Lang

NATURE COMMUNICATIONS 5 2014年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

Two-dimensional (2D) systems with continuous symmetry lack conventional long-range order because of thermal fluctuations. Instead, as pointed out by Berezinskii, Kosterlitz and Thouless (BKT), 2D systems may exhibit so-called topological order driven by the binding of vortex-antivortex pairs. Signatures of the BKT mechanism have been observed in thin films, specially designed heterostructures, layered magnets and trapped atomic gases. Here we report on an alternative approach for studying BKT physics by using a chemically constructed multilayer magnet. The novelty of this approach is to use molecular-based pairs of spin S = 1/2 ions, which, by the application of a magnetic field, provide a gas of magnetic excitations. On the basis of measurements of the magnetic susceptibility and specific heat on a so-designed material, combined with density functional theory and quantum Monte Carlo calculations, we conclude that these excitations have a distinct 2D character, consistent with a BKT scenario, implying the emergence of vortices and antivortices.

DOI： 10.1038/ncomms6169

Correlation effects in the tetragonal and collapsed-tetragonal phase of CaFe2As2 査読

Jean Diehl, Steffen Backes, Daniel Guterding, Harald O. Jeschke, Roser Valenti

PHYSICAL REVIEW B 90 ( 8 ) 2014年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

We investigate the role of correlations in the tetragonal and collapsed tetragonal phases of CaFe2As2 by performing charge self-consistent DFT+DMFT (density functional theory combined with dynamical mean-field theory) calculations. While the topology of the Fermi surface is basically unaffected by the inclusion of correlation effects, we find important orbital-dependent mass renormalizations which show good agreement with recent angle-resolved photoemission experiments. Moreover, we observe a markedly different behavior of these quantities between the low-pressure tetragonal and the high-pressure collapsed tetragonal phase. We attribute these effects to the increased hybridization between the iron and arsenic orbitals as one enters the collapsed tetragonal phase.

DOI： 10.1103/PhysRevB.90.085110

Electronic structure and de Haas-van Alphen frequencies in KFe2As2 within LDA plus DMFT 査読

Steffen Backes, Daniel Guterding, Harald O. Jeschke, Roser Valenti

NEW JOURNAL OF PHYSICS 16 2014年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

Recent density functional theory (DFT) calculations for KFe2As2 have been shown to be insufficient to satisfactorily describe angle-resolved photoemission (ARPES) measurements as well as observed de Haas-van Alphen (dHvA) frequencies. In the present work, we extend DFT calculations based on the full-potential linear augmented plane-wave method by dynamical mean field theory (DFT+DMFT) to include correlation effects beyond the local density approximation. We present results for two sets of reported crystal structures. Our calculations indicate that KFe2As2 is a moderately correlated metal with a mass renormalization factor of the Fe 3d orbitals between 1.6 and 2.7. Furthermore, the obtained shape and size of the Fermi surface are in good agreement with ARPES measurements and we observe some topological changes with respect to DFT calculations such as the opening of an inner hole cylinder at the Z point. As a result, our calculated dHvA frequencies differ greatly from existing DFT results and qualitatively agree with experimental data. On this basis, we argue that correlation effects are important to understand the -presently under debate-nature of the superconducting state in KFe2As2.

DOI： 10.1088/1367-2630/16/8/083025

Determination of magnetic form factors for organic charge-transfer salts: A first-principles investigation 査読

Francesc Salvat-Pujol, Harald O. Jeschke, Roser Valenti

PHYSICAL REVIEW B 90 ( 4 ) 2014年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

Organic charge-transfer salts show a variety of complex phases ranging from antiferromagnetic long-range order, spin liquid, bad metal, or even superconductivity. A powerful method to investigate magnetism is spin-polarized inelastic neutron scattering. However, such measurements have often been hindered in the past by the small size of available crystals as well as by the fact that the spin in these materials is distributed over molecular rather than atomic orbitals, and good estimates for the magnetic form factors are missing. By considering Wannier functions obtained from density-functional theory calculations, we derive magnetic form factors for a number of representative organic molecules. Compared to Cu2+, the form factors vertical bar F(q)vertical bar(2) fall off more rapidly as function of q, reflecting the fact that the spin density is very extended in real space. Form factors vertical bar F(q)vertical bar(2) for TMTTF, BEDT-TTF, and (BEDT-TTF)(2) have anisotropic and nonmonotonic structures.

DOI： 10.1103/PhysRevB.90.041101

Theoretical prediction of a strongly correlated Dirac metal 査読

I. I. Mazin, Harald O. Jeschke, Frank Lechermann, Hunpyo Lee, Mario Fink, Ronny Thomale, Roser Valenti

NATURE COMMUNICATIONS 5 2014年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

Recently, the most intensely studied objects in the electronic theory of solids have been strongly correlated systems and graphene. However, the fact that the Dirac bands in graphene are made up of sp(2) electrons, which are subject to neither strong Hubbard repulsion U nor strong Hund's rule coupling J, creates certain limitations in terms of novel, interaction-induced physics that could be derived from Dirac points. Here we propose GaCu3(OH)(6)Cl-2 (Ga-substituted herbertsmithite) as a correlated Dirac-Kagome metal combining Dirac electrons, strong interactions and frustrated magnetic interactions. Using density functional theory, we calculate its crystallographic and electronic properties, and observe that it has symmetry-protected Dirac points at the Fermi level. Its many-body physics is diverse, with possible charge, magnetic and superconducting instabilities. Through a combination of various many-body methods we study possible symmetry-lowering phase transitions such as Mott-Hubbard, charge or magnetic ordering, and unconventional superconductivity, which in this compound assumes an f-wave symmetry.

DOI： 10.1038/ncomms5261

Effect of isoelectronic doping on the honeycomb-lattice iridate A(2)IrO(3) 査読

S. Manni, Sungkyun Choi, I. I. Mazin, R. Coldea, Michaela Altmeyer, Harald O. Jeschke, Roser Valenti, P. Gegenwart

PHYSICAL REVIEW B 89 ( 24 ) 2014年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

We have investigated, experimentally and theoretically, the series (Na1-x Li-x)(2)IrO3. Contrary to what has been believed so far, only for x <= 0.25 does the system form uniform solid solutions where Li preferentially goes to the Ir2Na planes, as observed in our density functional theory calculations and consistent with x-ray diffraction analysis. For larger Li content, as evidenced by powder x-ray diffraction, scanning electron microscopy, and density functional theory calculations, the system shows a miscibility gap and a phase separation into an ordered Na3LiIr2O6 phase with alternating Na-3 and LiIr2O6 planes, and a Li-rich phase close to pure Li2IrO3. For x <= 0.25 we observe (1) an increase of c/a with Li doping up to x = 0.25, despite the fact that c/a in pure Li2IrO3 is smaller than in Na2IrO3, and (2) a gradual reduction of the antiferromagnetic ordering temperature T-N and ordered moment. In view of our results showing clear evidence for phase separation for 0.25 <= x <= 0.6, more detailed studies are needed to confirm the presence or absence of phase separation at the higher doping x similar to 0.7, where a continuum quantum phase transition has been proposed previously.

DOI： 10.1103/PhysRevB.89.245113

Unveiling the microscopic nature of correlated organic conductors: The case kappa-(ET)(2)Cu[N(CN)(2)]BrxCl1-x 査読

Johannes Ferber, Kateryna Foyevtsova, Harald O. Jeschke, Roser Valent

PHYSICAL REVIEW B 89 ( 20 ) 2014年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

A few organic conductors show a diversity of exciting properties like Mott insulating behavior, spin liquid, antiferromagnetism, bad metal, or unconventional superconductivity controlled by small changes in temperature, pressure, or chemical substitution. While such a behavior can be technologically relevant for functional switches, a full understanding of its microscopic origin is still lacking and poses a challenge in condensed matter physics since these phases may be a manifestation of electronic correlation. Here we determine from first principles the microscopic nature of the electronic phases in the family of organic systems kappa-(ET)(2)Cu[N(CN)(2)]BrxCl1- x by a combination of density functional theory calculations and the dynamical mean field theory approach in a form adapted for organic systems. By computing spectral and optical properties we are able to disentangle the origin of the various optical transitions in these materials and prove that correlations are responsible for relevant features. Remarkably, while some transitions are inherently affected by correlations, others are completely uncorrelated. We discuss the consequences of our findings for the phase diagram in these materials.

DOI： 10.1103/PhysRevB.89.205106

Dynamics of tungsten hexacarbonyl, dicobalt octacarbonyl, and their fragments adsorbed on silica surfaces 査読

Kaliappan Muthukumar, Roser Valenti, Harald O. Jeschke

JOURNAL OF CHEMICAL PHYSICS 140 ( 18 ) 2014年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

Tungsten and cobalt carbonyls adsorbed on a substrate are typical starting points for the electron beam induced deposition of tungsten or cobalt based metallic nanostructures. We employ first principles molecular dynamics simulations to investigate the dynamics and vibrational spectra of W(CO)(6) and W(CO)(5) as well as Co-2(CO)(8) and Co(CO)(4) precursor molecules on fully and partially hydroxylated silica surfaces. Such surfaces resemble the initial conditions of electron beam induced growth processes. We find that both W(CO)(6) and Co-2(CO)(8) are stable at room temperature and mobile on a silica surface saturated with hydroxyl groups (OH), moving up to half an Angstrom per picosecond. In contrast, chemisorbed W(CO)(5) or Co(CO)(4) ions at room temperature do not change their binding site. These results contribute to gaining fundamental insight into how the molecules behave in the simulated time window of 20 ps and our determined vibrational spectra of all species provide signatures for experimentally distinguishing the form in which precursors cover a substrate. (C) 2014 AIP Publishing LLC.

DOI： 10.1063/1.4873584

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