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

• dynamics (MD) simulations of the SAM. In the QM approach, the stiffness of the SAM is first related to a molecular quantity, the weighted molecular force constant , through a simple model. Then, is obtained by rigorous ab initio calculations (details in Experimental section). The molecular

• : These vibrational frequencies, reduced masses and normal modes were obtained by ab initio QM calculations. A full geometry optimization of the electronic ground state of 1-DA, 2-DA, and 3-DA, both trans- and cis-isomers, was obtained in the vacuum phase at the level of density functional theory (DFT) by

An MCBJ case study: The influence of π-conjugation on the single-molecule conductance at a solid/liquid interface

• Wenjing Hong,
• Hennie Valkenier,
• Gábor Mészáros,
• David Zsolt Manrique,
• Artem Mishchenko,
• Alexander Putz,
• Pavel Moreno García,
• Colin J. Lambert,
• Jan C. Hummelen and
• Thomas Wandlowski

Beilstein J. Nanotechnol. 2011, 2, 699–713, doi:10.3762/bjnano.2.76

• and the Fermi levels of the leads, based on a comparison with ab initio transport calculations and the corresponding transmission curves [58]. For comparison with the conductance–distance measurements shown in Figure 4, we calculated the slopes of the linear parts (typically in the range between −0.30

• than that of AC. This trend demonstrates that the cross-conjugated motif of AQ indeed gives rise to a lower conductance as compared to the linear-conjugated AC, which is in agreement with ab initio transport calculations predicting a destructive quantum interference present in AQ, but which is absent

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

• conformationally flexible molecules. Due to its conceptual simplicity and the ready availability of reliable empirical force fields (or forces computed ab initio), molecular dynamics is currently the most popular method for determining anharmonic frequencies of large systems (see [7] for an overview of some

• process. This is due to the necessity to first construct a potential energy surface (PES), which is then used to compute the vibrational Hamiltonian. The PES can also be generated directly from ab initio programs (direct-VSCF), thus leading to a straightforward route from electronic structure theory to a

• initio techniques. Thus, in this method, the speed at which the PES can be computed is directly related to the number of mode–mode couplings taken into account and to the amount of computing power allocated to the ab initio calculation of each grid point. However, the latter constitutes one of the main

Charge transfer through single molecule contacts: How reliable are rate descriptions?

• Denis Kast,
• L. Kecke and
• J. Ankerhold

Beilstein J. Nanotechnol. 2011, 2, 416–426, doi:10.3762/bjnano.2.47

• molecular electronics in the last decade. However, a theoretical description of molecular contacts as the building blocks of future devices is challenging, as it has to combine the properties of Fermi liquids in the leads with charge and phonon degrees of freedom on the molecule. Outside of ab initio

• orders of magnitude less expensive than elaborate numerical simulations that, however, provide exact solutions as benchmarks. Adjustable parameters obtained, e.g., from ab initio calculations allow for the treatment of various realizations. Even though not as rigorously formulated as, e.g

• experimental data. For this purpose, basically two strategies have been followed. One is based on ab initio schemes that have been successfully employed for isolated molecular structures, such as, e.g., density functional theory (DFT). Combining DFT with nonequilibrium Green’s functions (NEGF) allows us to

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

• changes in the electronic state, such as electron energy loss spectroscopy [4] or scanning tunneling microscopy [5], make use of advanced simulation methods to model the specimen. In 1997, Gemming and Möbus performed ab-initio HRTEM simulations of ionic crystals and justified the use of conventional image

Influence of water on the properties of an Au/Mpy/Pd metal/molecule/metal junction

• Jan Kučera and
• Axel Groß

Beilstein J. Nanotechnol. 2011, 2, 384–393, doi:10.3762/bjnano.2.44

• for the stability in the water complex. Ab initio molecular dynamics simulations showed that at room temperature the hexagonal water bilayer structure on bulk metal surfaces becomes disordered [19], but it may persist on the Au/Mpy/Pd junction because of the higher stability of the H2O layer, which is

• thus can not explain the experimentally observed strong reduction of the DOS of the Pd layer in the junction at the Fermi energy. Experimental Self-consistent periodic DFT calculations were performed employing the Vienna ab initio simulation package (VASP) [33]. The exchange-correlation effects were

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

• alloy in one specific case by means of large scale ab initio total energy calculations in the framework of density functional theory. For representative system sizes in the range of a few nanometers, where the surface-to-volume ratio is balanced and competitive effects should be expected such

• % surface atoms characterized by a reduced coordination in the first neighbor shell and are thus predetermined to monitor the competition between surface and bulk contributions with changing valence electron number. Computational The calculations were carried out using the Vienna Ab-initio Simulation

• restriction was also made for the 4d and 5d elements. This has proven to be a reasonable compromise in a recent ab initio study of the lattice dynamics of ordered Fe rich alloys with Pt group elements [50]. For a few selected isomers, single-point calculations with an increased value Ecut = 335 eV were