Constant chemical potential approach for quantum chemical calculations in electrocatalysis

• Wolfgang B. Schneider and
• Alexander A. Auer

Beilstein J. Nanotechnol. 2014, 5, 668–676, doi:10.3762/bjnano.5.79

• a real molecular system of isolated active sites on a surface. However, metallic systems at finite temperature with high or infinite density of states and small or vanishing bandgap, show a continuous change of the potential with the number of electrons. Furthermore, in the framework of a Grand

Effects of the preparation method on the structure and the visible-light photocatalytic activity of Ag₂CrO₄

• Difa Xu,
• Shaowen Cao,
• Jinfeng Zhang,
• Bei Cheng and
• Jiaguo Yu

Beilstein J. Nanotechnol. 2014, 5, 658–666, doi:10.3762/bjnano.5.77

• scattering with a zetasizer (Nano ZS90, Malvern, UK). Computational details The DFT calculations were carried out to investigate the band structure and density of states (DOS) of Ag2CrO4 model by using the CASTEP Packages on the basis of the plane-wave-pseudo-potential approach [77][78]. Combined with

• inset) and the corresponding colours (lower left inset) of Ag2CrO4 samples prepared by different methods: (a) microemulsion, (b) precipitation, and (c) hydrothermal. Band structure plots (a) and density of states (b) for Ag2CrO4. Photocatalytic degradation of MB aqueous solution over Ag2CrO4 samples

Analytical development and optimization of a graphene–solution interface capacitance model

• Hediyeh Karimi,
• Rasoul Rahmani,
• Reza Mashayekhi,
• Leyla Ranjbari,
• Amir H. Shirdel,
• Niloofar Haghighian,
• Parisa Movahedi,
• Moein Hadiyan and
• Razali Ismail

Beilstein J. Nanotechnol. 2014, 5, 603–609, doi:10.3762/bjnano.5.71

• geometrical capacitance of the double layer/graphene interface to model the accumulation of a layer of counter-ions on a charged electrode. Finally, CQ is the quantum capacitance of the EGFET associated with the finite density of states of graphene [24]. Figure 2 shows that VG has a strong influence on the

Interaction of iron phthalocyanine with the graphene/Ni(111) system

• Lorenzo Massimi,
• Simone Lisi,
• Daniela Pacilè,
• Carlo Mariani and
• Maria Grazia Betti

Beilstein J. Nanotechnol. 2014, 5, 308–312, doi:10.3762/bjnano.5.34

• , and on Gr/Ir for comparison, as a function of the thickness of the FePc layer is shown in Figure 2. The FePc adsorption on Gr/Ni(111) produces a general reduction of the prevalent d band spectral density of states and a new feature emerges close to the Fermi level (at about 0.3 eV BE). Its intensity

• the Fermi level for a coverage of 0.3 and 1 SL of FePc is given. Valence band spectral density of states of clean Ni(111) (red line), of Gr/Ni(111) and of 0.2 SL FePc onto Gr/Ni (black lines), taken at the K point of the BZ (±2° angular integration around K, with 21.218 eV photon energy

Charge and spin transport in mesoscopic superconductors

• M. J. Wolf,
• F. Hübler,
• S. Kolenda and
• D. Beckmann

Beilstein J. Nanotechnol. 2014, 5, 180–185, doi:10.3762/bjnano.5.18

• , the effect of the applied field is mostly orbital pair breaking, and the Zeeman splitting of the density of states does not play a significant role. In Figure 2a, we show the nonlocal conductance gnl of a pair of contacts at low temperature and for bias voltages above the energy gap Δ ≈ 200 μeV of the

• length at low temperature where N1 is the density of states in the superconductor, N2 is the real part of the anomalous Green’s function, is the dirty-limit coherence length, and DN is the normal-state diffusion coefficient. The nonlocal conductance due to charge imbalance within the same approximation

• polarity. These features can be attributed to spin injection into the Zeeman-split density of states of the superconductor [17][18][22][26], which is probed by the ferromagnetic detector in this configuration. Spin-polarized tunneling can be described by two independent conductances g↓ and g↑ for the two

Core level binding energies of functionalized and defective graphene

• Toma Susi,
• Markus Kaukonen,
• Paula Havu,
• Mathias P. Ljungberg,
• Paola Ayala and
• Esko I. Kauppinen

Beilstein J. Nanotechnol. 2014, 5, 121–132, doi:10.3762/bjnano.5.12

• the graphene plane was sufficient to ensure convergence in all cases, including the highly non-planar -COOH functional group. All structures were allowed to fully relax so that the maximum forces reached less than 0.01 eV/atom. The all-electron projected density of states of the pristine graphene

Quantum size effects in TiO₂ thin films grown by atomic layer deposition

• Massimo Tallarida,
• Chittaranjan Das and
• Dieter Schmeisser

Beilstein J. Nanotechnol. 2014, 5, 77–82, doi:10.3762/bjnano.5.7

• calculation of unoccupied density of states performed by Vayssieres et al. [10] indicate the presence of Ti 4s/O 2p states over a large energy range. Our spectrum of the 0.75 nm film agrees with the calculation of Vayssieres especially in the region of peak D1, while peak D2 does not have any visible

Influence of particle size and fluorination ratio of CF_x precursor compounds on the electrochemical performance of C–FeF₂ nanocomposites for reversible lithium storage

• Ben Breitung,
• M. Anji Reddy,
• Venkata Sai Kiran Chakravadhanula,
• Michael Engel,
• Christian Kübel,
• Annie K. Powell,
• Horst Hahn and
• Maximilian Fichtner

Beilstein J. Nanotechnol. 2013, 4, 705–713, doi:10.3762/bjnano.4.80

• . For C(FeF2)0.5_300 the same G-mode position was measured, but the I(D)/I(G) ratio decreased to 1.73. During a transition from nanocrystalline graphite to amorphous carbon the VDOS (vibrational density of states) of graphite changes, the D-mode intensity decreases and the G mode retains its intensity

Structural and thermoelectric properties of TMGa₃ (TM = Fe, Co) thin films

• Sebastian Schnurr,
• Ulf Wiedwald,
• Paul Ziemann,
• Valeriy Y. Verchenko and
• Andrei V. Shevelkov

Beilstein J. Nanotechnol. 2013, 4, 461–466, doi:10.3762/bjnano.4.54

• sharp features in the electronic density of states (DOS) close to the Fermi level, which are expected to be quite beneficial for an enhanced thermoelectric response [5][6]; large Seebeck coefficients of −350 μV/K [7] or even −563 μV/K [8] at room temperature were reported for bulk FeGa3. Recently, we

• found the existence of an unlimited solid solution between the isostructural intermetallics FeGa3 and CoGa3 [9]. With an increasing cobalt content in the Fe1−xCoxGa3 solid solution, the Fermi level shifts up to the conduction band and crosses peaks of high electronic density of states, ultimately

• and the nuclear quadrupole resonance (NQR) investigations of the nuclear spin–lattice relaxation rate. In line with these results, the Fe1−xCoxGa3 solid solution was found to behave as a metal for x > 0.025. For smaller values of x the system remains non-metallic, while the density of states at the

Synthesis and thermoelectric properties of Re₃As_6.6In_0.4 with Ir₃Ge₇ crystal structure

• Valeriy Y. Verchenko,
• Anton S. Vasiliev,
• Alexander A. Tsirlin,
• Vladimir A. Kulbachinskii,
• Vladimir G. Kytin and
• Andrei V. Shevelkov

Beilstein J. Nanotechnol. 2013, 4, 446–452, doi:10.3762/bjnano.4.52

• atoms occupying the 16f site, with a bond distance of 2.538(5) Å. Clearly, indium does not favor such a short bond to arsenic and, therefore, avoids the occupation of this site. Electronic structure, magnetic and thermoelectric properties The computed density of states for Re3As7 is shown in Figure 5

• ∙∂N(EF)/∂E [19], provided that the system is made semiconducting by doping. Indeed, the absolute values of S for Re3As6.4Ge0.6 exceed 150 µV·K−1 at high temperatures, thus leading to high values of ZT [13]. In Re3As7, the calculated density of states at E = EF is 8.3 states/(eV·f.u.). For the solid

• Re3As7−xInx. Density-of-states curve for Re3As7. Re contribution: dashed line, As1 and As2: light and dark gray lines, respectively. Magnetic susceptibility-versus-temperature plots for the Re3As7 and S1 samples. The contribution of core diamagnetism is shown as a dash-dotted line. Thermoelectric

In situ monitoring magnetism and resistance of nanophase platinum upon electrochemical oxidation

• Eva-Maria Steyskal,
• Stefan Topolovec,
• Stephan Landgraf,
• Heinz Krenn and
• Roland Würschum

Beilstein J. Nanotechnol. 2013, 4, 394–399, doi:10.3762/bjnano.4.46

• electrochemically induced oxygen adsorption nicely fits with earlier studies of the influence of chemisorbed oxygen on the magnetic susceptibility of Pt [19]. The trend of decreasing magnetic moment is also supported by recent DFT calculations according to which the density of states at the Fermi level of Pt

• to an increase of the density of states rather than to a decrease. Although oxygen adsorption causes a decrease of the magnetic moment, it may not fully account for the observed voltage-induced variation of m. In fact, in contrast to the voltage-induced variation of R, the Δm/m0–U behavior shows no

Influence of diffusion on space-charge-limited current measurements in organic semiconductors

• Thomas Kirchartz

Beilstein J. Nanotechnol. 2013, 4, 180–188, doi:10.3762/bjnano.4.18

• of current–voltage curves, current–voltage curves are simulated for different concentrations of traps using a drift–diffusion solver, and then analytical equations are fitted to the simulated curves to compare the apparent mobility and density of states derived from the fit to the ones that were used

• decaying density of states. Details of the simulation The simulations are performed by using a commercial device simulator called Advanced Semiconductor Analysis (ASA) that was developed by the group of M. Zeman at the TU Delft (Netherlands) [32][33]. The software solves the Poisson equation and the

Electronic and transport properties of kinked graphene

• Jesper Toft Rasmussen,
• Tue Gunst,
• Peter Bøggild,
• Antti-Pekka Jauho and
• Mads Brandbyge

Beilstein J. Nanotechnol. 2013, 4, 103–110, doi:10.3762/bjnano.4.12

• a (25,25) nanotube. Experiments by Ruffieux et al. [38] compare hydrogen adsorption on C60 molecules, CNTs, and graphite to show that reactivity is increased with curvature. In our case we find that the local electronic density of states changes little for the atoms on the pristine bent graphene

Structural and electronic properties of oligo- and polythiophenes modified by substituents

• Simon P. Rittmeyer and
• Axel Groß

Beilstein J. Nanotechnol. 2012, 3, 909–919, doi:10.3762/bjnano.3.101

• within the unit cell as well as the width of the unit cell were optimized as the latter correlates directly with the intercellular bond length. For molecules, calculations concerning the density of states (DOS) were carried out at the Γ point with a Gaussian smearing (σ = 0.01 eV). For polymers, in

• effort in plane-wave codes such as VASP. As we are mainly interested in trends in the local density of states depending on the choice of the substituent, GGA-DFT calculations should be sufficient to reproduce these trends. However, one has to be aware that all absolute values of HOMO–LUMO and band gaps

• that modeling a polymer consisting of exclusively 3,4-connected thiophene monomers with a two-ring unit cell is not possible because of steric hindrance. Figure 2 compares the density of states for PTp and α,β-PTp. Obviously, there is a considerable difference in the band gap of both isomers. As

Pure hydrogen low-temperature plasma exposure of HOPG and graphene: Graphane formation?

• Baran Eren,
• Dorothée Hug,
• Laurent Marot,
• Rémy Pawlak,
• Marcin Kisiel,
• Roland Steiner,
• Dominik M. Zumbühl and
• Ernst Meyer

Beilstein J. Nanotechnol. 2012, 3, 852–859, doi:10.3762/bjnano.3.96

• around the step edges of graphite, where the step edges were terminated with atomic hydrogen [38]. Since STM probes the local density of states [37], this distortion in the ring patterns may arise from surface corrugation [38]. On the other hand, it should not be disregarded that graphane has different

Towards atomic resolution in sodium titanate nanotubes using near-edge X-ray-absorption fine-structure spectromicroscopy combined with multichannel multiple-scattering calculations

• Carla Bittencourt,
• Peter Krüger,
• Maureen J. Lagos,
• Xiaoxing Ke,
• Gustaaf Van Tendeloo,
• Chris Ewels,
• Polona Umek and
• Peter Guttmann

Beilstein J. Nanotechnol. 2012, 3, 789–797, doi:10.3762/bjnano.3.88

• )TiNTs. As the core hole was found to have a negligible effect on the O K-edge NEXAFS spectra of TiO2, the absorption spectra can be modeled by using the O p projected ground-state density of states (DOS) [42]. The DOS was broadened with a Lorentzian of energy-dependent width, to account for finite core

Focused electron beam induced deposition: A perspective

• Michael Huth,
• Fabrizio Porrati,
• Christian Schwalb,
• Marcel Winhold,
• Roland Sachser,
• Maja Dukic,
• Jonathan Adams and
• Georg Fantner

Beilstein J. Nanotechnol. 2012, 3, 597–619, doi:10.3762/bjnano.3.70

• composition ratio [Si]/[Pt] = 1 and 3/2 indicates a granular electronic density of states of the FEBID samples. The minimal resistivity of the [Si]/[Pt] = 3/2 sample provides evidence that the intergranular tunnel-coupling strength is largest for this sample. On the other hand, from the TEM measurements no

• special microstructural feature, such as re-entrant crystallization of the granules, has been observed. It thus remains an unresolved issue, whether the granular electronic density of states is indeed indicative of the formation of an amorphous precursor of the metastable, hexagonal and superconducting

• the grain volume (r: grain radius) and NF denotes the density of states at the chemical potential. For typical grain sizes in FEBID structures with a diameter of a few nanometers, δ/kB (kB: Boltzmann constant) is of the order of 1 K for metallic grains with a density of states on the order of 1 (eVnm3

P-wave Cooper pair splitting

• Henning Soller and
• Andreas Komnik

Beilstein J. Nanotechnol. 2012, 3, 493–500, doi:10.3762/bjnano.3.56

• , where α = F1, F2 using the Stoner model with an exchange energy hex as in [43] Consequently they can be described as fermionic continua with a spin-dependent density of states (DOS) ρ0,α,σ = ρ0,α(1 + σPα), where Pα is the polarization. The superconductor is described by using the ordinary s-wave BCS

• Hamiltonian We express the energies of the dot and the reservoirs relative to the superconductor chemical potential [44] such that μS = 0 and Vα = μS − μα = −μα is the chemical potential of the ferromagnets. The quasiparticle density of states in the superconductor has the form: , where ρ0S is constant in the

Structural, electronic and photovoltaic characterization of multiwalled carbon nanotubes grown directly on stainless steel

• Luca Camilli,
• Manuela Scarselli,
• Silvano Del Gobbo,
• Paola Castrucci,
• Eric Gautron and
• Maurizio De Crescenzi

Beilstein J. Nanotechnol. 2012, 3, 360–367, doi:10.3762/bjnano.3.42

• responsible for the generation of photocurrent in SWCNTs. Since in the electronic density of states of MWCNTs such a singularity is still present [9], we think that the experimentally measured shoulder should have the same origin. Shyu and Lin report a complete calculation of these energy-loss features

X-ray absorption spectroscopy by full-field X-ray microscopy of a thin graphite flake: Imaging and electronic structure via the carbon K-edge

• Carla Bittencourt,
• Adam P. Hitchock,
• Xiaoxing Ke,
• Gustaaf Van Tendeloo,
• Chris P. Ewels and
• Peter Guttmann

Beilstein J. Nanotechnol. 2012, 3, 345–350, doi:10.3762/bjnano.3.39

• unoccupied density of states, although the energies and intensities are modified by core–hole interactions [15]. When linearly polarized X-rays are used the carbon K-edge of graphene materials exhibits a strong linear dichroism, which can be used to probe local anisotropy and structural order [16]. When

qPlus magnetic force microscopy in frequency-modulation mode with millihertz resolution

• Maximilian Schneiderbauer,
• Daniel Wastl and
• Franz J. Giessibl

Beilstein J. Nanotechnol. 2012, 3, 174–178, doi:10.3762/bjnano.3.18

• -polarized tip and the spin-dependent local density of states of the sample (Figure 1b). STM is unable to probe insulating surfaces but AFM can be used: The antiferromagnetic surface structure of NiO (001) was imaged by Magnetic Exchange Force Microscopy (MExFM) [5]. In MExFM the magnetic exchange force

Current-induced forces in mesoscopic systems: A scattering-matrix approach

• Niels Bode,
• Silvia Viola Kusminskiy,
• Reinhold Egger and
• Felix von Oppen

Beilstein J. Nanotechnol. 2012, 3, 144–162, doi:10.3762/bjnano.3.15

• factors of the density of states in the leads into the coupling matrix W for notational simplicity. Note that we allow W to depend on energy. (Compare with the wide-band limit discussed in [22], which employs an energy-independent hybridization Γ.) Dyson’s equation for the retarded Green’s function can

Transmission eigenvalue distributions in highly conductive molecular junctions

• Justin P. Bergfield,
• Joshua D. Barr and
• Charles A. Stafford

Beilstein J. Nanotechnol. 2012, 3, 40–51, doi:10.3762/bjnano.3.5

• each Pt tip, we include one s, three p and five d orbitals in our calculations, which represent the evanescent tunneling modes in free space outside the apex atom of the tip. At room temperature, the Pt density of states (DOS) ρα(E) = Σlρlα(E) is sharply peaked around the Fermi energy [26] with ρα(εF

• the quasi-atomic wavefunctions of the atomically sharp electrode are relevant. In this case we may express the elements of Γα as [6] where the sum is calculated over the evanescent tunneling modes emanating from the metal tip, labeled by their angular-momentum quantum numbers, is the local density of

• states on the apex atom of electrode α, and is the tunneling matrix element of orbitals l [25]. The constants Cl can in principle be determined by matching the evanescent tip modes to the wavefunctions within the metal tip [25]; however, we set and determine the constant C by fitting to the peak of the

When “small” terms matter: Coupled interference features in the transport properties of cross-conjugated molecules

• Gemma C. Solomon,
• Justin P. Bergfield,
• Charles A. Stafford and
• Mark A. Ratner

Beilstein J. Nanotechnol. 2011, 2, 862–871, doi:10.3762/bjnano.2.95

• to each electrode, with coupling strength γ = βS/3 = −1 eV. For this system we have: The transmission is then calculated by using the nonequilibrium Green’s function formalism assuming the wide-band limit for the density of states of the electrodes and setting where ρ is the density of states of the

• Green’s functions in the same way as the Hückel model calculations, that is simply by using the gDFTB Hamiltonian in place of the Hückel Hamiltonian. A wide-band approximation is also employed in which the density of states used to construct the self-energies is set to a value for bulk gold (1.9 eV −1

Current-induced dynamics in carbon atomic contacts

• Jing-Tao Lü,
• Tue Gunst,
• Per Hedegård and
• Mads Brandbyge

Beilstein J. Nanotechnol. 2011, 2, 814–823, doi:10.3762/bjnano.2.90

• the frequency (energy) domain. This can be expressed by using the coupling-weighted electron–hole-pair density of states, Λαβ, inside or between electrodes α,β L,R, where Λ can be expressed in terms of the electrode DOS, We have included a factor of 2 from the spin degeneracy and have explicitly