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

• basis set up to a cutoff energy of 400 eV, which was checked for convergence. All geometrical optimizations were carried out by using the conjugated gradient algorithm implemented in VASP. Molecules were geometrically optimized by using a sufficiently large unit cell in the supercell approach and one k

• -point. In contrast, the polymers were described as one-dimensional infinite chains with a 7 × 1 × 1 k-point sampling to replace the integration over the one-dimensional first Brillouin zone. k-Point convergence was carefully checked. When optimizing the polymer structure, both the geometric structure

Models of the interaction of metal tips with insulating surfaces

• Thomas Trevethan,
• Matthew Watkins and
• Alexander L. Shluger

Beilstein J. Nanotechnol. 2012, 3, 329–335, doi:10.3762/bjnano.3.37

• observed force difference. The polarizability could be affected by the quality of the basis set, k-point sampling and the pseudopotential used (the plane-wave code uses a pseudopotential constructed with Cr in a d5s1 state, whilst the present calculations include s2p6d5s1). At present, the full convergence

Direct monitoring of opto-mechanical switching of self-assembled monolayer films containing the azobenzene group

• Einat Tirosh,
• Enrico Benassi,
• Silvio Pipolo,
• Marcel Mayor,
• Michal Valášek,
• Veronica Frydman,
• Stefano Corni and
• Sidney R. Cohen

Beilstein J. Nanotechnol. 2011, 2, 834–844, doi:10.3762/bjnano.2.93

• using the Becke three-parameter Lee–Yang–Parr (B3LYP) exchange–correlation functional with cc-pVTZ basis set. The optimized geometries were then subject to vibration calculation in order to compute the vibrational properties and to investigate whether the convergence points were genuine energy minima

Towards quantitative accuracy in first-principles transport calculations: The GW method applied to alkane/gold junctions

• Mikkel Strange and
• Kristian S. Thygesen

Beilstein J. Nanotechnol. 2011, 2, 746–754, doi:10.3762/bjnano.2.82

• electrode and thus also describe screening effects to some extent in this region. The rather fast convergence of the screening effects with extended molecule size can be probed directly through a simple approach based on a constrained DFT calculation where the number of electrons on the molecule is

Deconvolution of the density of states of tip and sample through constant-current tunneling spectroscopy

• Holger Pfeifer,
• Berndt Koslowski and
• Paul Ziemann

Beilstein J. Nanotechnol. 2011, 2, 607–617, doi:10.3762/bjnano.2.64

• criterion available to determine a better choice. In the following examples we achieved better results, i.e., faster convergence and better accuracy, when starting with data for the smaller set current. Note also, as previously reported [7][13], that numerical errors may accumulate during the iterations

Towards a scalable and accurate quantum approach for describing vibrations of molecule–metal interfaces

• David M. Benoit,
• Bruno Madebene,
• Inga Ulusoy,
• Luis Mancera,
• Yohann Scribano and
• Sergey Chulkov

Beilstein J. Nanotechnol. 2011, 2, 427–447, doi:10.3762/bjnano.2.48

• terms, two-dimensional couplings, three-dimensional couplings, etc. This expansion guarantees convergence, as a 3Na − 6 dimensional expansion describes the complete PES for a problem consisting of Na atoms in the case of an isolated molecule. Note that other representations, such as polynomial

• expansions, do not necessarily possess such well defined multi-dimensional convergence properties. For large systems, Gerber et al. [10] have shown that a truncation of the expansion to two-dimensional (2-D) couplings built on the normal modes of the system is sufficiently accurate for most applications

• sufficient for most applications, and convergence with respect to Ng is easily checked. This leads to a relatively small computational burden on the diagonalisation routines. As the potential energy is usually computed ab initio on a grid that is sparser than Ng, the 1-D PES is interpolated using a cubic

Simulation of bonding effects in HRTEM images of light element materials

• Simon Kurasch,
• Jannik C. Meyer,
• Daniela Künzel,
• Axel Groß and
• Ute Kaiser

Beilstein J. Nanotechnol. 2011, 2, 394–404, doi:10.3762/bjnano.2.45

• is always necessary to do convergence tests of the main parameters such as k-points and basis set size [22]. Usually the convergence is tested with respect to the total energy and the electric field gradients. This was done using ideal graphene as a test structure. Interestingly, we find that the

• 43: WIEN2k convergence tests for ideal graphene Supporting Information File 44: Program to get 3D WIEN2k potentials (Phyton script, rename to .py). Acknowledgements We gratefully acknowledge financial support by the German Research Foundation (DFG) within research project SFB 569 “Hierarchic

Effect of large mechanical stress on the magnetic properties of embedded Fe nanoparticles

• Srinivasa Saranu,
• Sören Selve,
• Ute Kaiser,
• Luyang Han,
• Ulf Wiedwald,
• Paul Ziemann and
• Ulrich Herr

Beilstein J. Nanotechnol. 2011, 2, 268–275, doi:10.3762/bjnano.2.31

• similar behaviour before and after loading, whereas the FC curves differ for both samples. As a result, the temperature above which the FC and the ZFC curves fall together (called convergence temperature Tcon here) shifts from about Tcon= 170 K in the as-prepared state to about Tcon = 220 K after H

Structural and magnetic properties of ternary Fe_1–xMn_xPt nanoalloys from first principles

• Markus E. Gruner and
• Peter Entel

Beilstein J. Nanotechnol. 2011, 2, 162–172, doi:10.3762/bjnano.2.20

• . The structural relaxations were stopped when the energy difference between two consecutive relaxations was less than 0.1 meV, leading to a convergence of forces down to the order of 10 meV/Å. The symmetrization of wavefunctions and forces was consistently switched off in all calculations. The

On the reticular construction concept of covalent organic frameworks

• Binit Lukose,
• Agnieszka Kuc,
• Johannes Frenzel and
• Thomas Heine

Beilstein J. Nanotechnol. 2010, 1, 60–70, doi:10.3762/bjnano.1.8

• the DFTB+ code on elementary unit cells in order to validate the calculations within the Γ-point approximation. The number of k-points has been determined by reaching convergence for the total energy as a function of k-points according to the scheme proposed by Monkhorst and Pack [27]. Band structures