CO-oxidation on Pt(110); Scanning Tunneling Microscopy inside a high-pressure flow-reactor

Quantum Matter and Optic

Rational and intuitive approaches to music composition: The impact of individual differences in thinking/learning styles on compositional processes

This study explores the idea that there are two different types of composers, those that use a rational process of composition involving pre-planning and use of external systems and those that use an intuitive process that involves trial and error or other exploratory means for composing. It focuses on further understanding these patterns of thought as they are found in the compositional processes of student composers as well as investigating their learning preferences. The study examines the compositional processes of five composition students from the Sydney Conservatorium of Music selected using their results on the SOLAT (Style Of Learning And Thinking) measure (Torrance, McCarthy & Kolesinski, 1988). After interviewing the five participants, a model was developed that explained how rational and intuitive patterns of thought were used at different levels. The macroprocesses of participants were found to sit on a continuum between rational and intuitive whilst at the micro-level participants were seen to use a mixture of both processes. The interview participants were also asked to comment on their preferred activities for learning composition. It was found that the participants believed their compositional processes were something that they developed themselves and they wanted a more personal approach to learning. The findings have implications for both teachers of composition and their students

Electron scattering effects at physisorbed hydrogen molecules on break-junction electrodes and nanowires formation in hydrogen environment

The physisorption of hydrogen molecules on the surface of gold and other coinage metals was studied using distance tunneling spectroscopy. We observed strong N-shaped deviation of the tunnel current (resistance) vs distance dependences from the exponential one. Such deviations are difficult to explain in the framework of the Tersoff–Hamann approximation. We suggest the scattering of the tunneling electrons by H₂ molecules as origin for observed effect. We found that this phenomenon is also common for strongly adsorbed organic molecules with one anchoring group. Pulling Au, Cu and Pt nanowires at 22 K in hydrogen environment show that the electrodes of break junctions are still connected up to very low conductances of 10⁻⁴–10⁻⁶ G₀ through hydrogen–metal one-atom chains

Insights into the function of silver as an oxidation catalyst by ab initio, atomistic thermodynamics

To help understand the high activity of silver as an oxidation catalyst, e.g., for the oxidation of ethylene to epoxide and the dehydrogenation of methanol to formaldehyde, the interaction and stability of oxygen species at the Ag(111) surface has been studied for a wide range of coverages. Through calculation of the free energy, as obtained from density-functional theory and taking into account the temperature and pressure via the oxygen chemical potential, we obtain the phase diagram of O/Ag(111). Our results reveal that a thin surface-oxide structure is most stable for the temperature and pressure range of ethylene epoxidation and we propose it (and possibly other similar structures) contains the species actuating the catalysis. For higher temperatures, low coverages of chemisorbed oxygen are most stable, which could also play a role in oxidation reactions. For temperatures greater than about 775 K there are no stable oxygen species, except for the possibility of O atoms adsorbed at under-coordinated surface sites Our calculations rule out thicker oxide-like structures, as well as bulk dissolved oxygen and molecular ozone-like species, as playing a role in the oxidation reactions.Comment: 15 pages including 9 figures, Related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Ab initio atomistic thermodynamics and statistical mechanics of surface properties and functions

Previous and present "academic" research aiming at atomic scale understanding is mainly concerned with the study of individual molecular processes possibly underlying materials science applications. Appealing properties of an individual process are then frequently discussed in terms of their direct importance for the envisioned material function, or reciprocally, the function of materials is somehow believed to be understandable by essentially one prominent elementary process only. What is often overlooked in this approach is that in macroscopic systems of technological relevance typically a large number of distinct atomic scale processes take place. Which of them are decisive for observable system properties and functions is then not only determined by the detailed individual properties of each process alone, but in many, if not most cases also the interplay of all processes, i.e. how they act together, plays a crucial role. For a "predictive materials science modeling with microscopic understanding", a description that treats the statistical interplay of a large number of microscopically well-described elementary processes must therefore be applied. Modern electronic structure theory methods such as DFT have become a standard tool for the accurate description of individual molecular processes. Here, we discuss the present status of emerging methodologies which attempt to achieve a (hopefully seamless) match of DFT with concepts from statistical mechanics or thermodynamics, in order to also address the interplay of the various molecular processes. The new quality of, and the novel insights that can be gained by, such techniques is illustrated by how they allow the description of crystal surfaces in contact with realistic gas-phase environments.Comment: 24 pages including 17 figures, related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Influence of atomic structure, steps, and kinks on the catalytic activity: In situ surface studies

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Pushing the limits of SPM

Quantum Matter and Optic

Ultra-flat coplanar electrodes for controlled electrical contact of molecular films

Contains fulltext : 92524.pdf (publisher's version ) (Open Access

STM tip induced creation and annihilation of small Ge clusters and missing dimer vacancies on Ge(001)

We have observed the appearance and disappearance of small Ge clusters and missing dimer vacancies on Ge(001) during scanning with a scanning tunneling microscope (STM) under standard tunneling conditions at room temperature. We claim that these processes are induced by the STM tip. Moreover, we emphasize that the observed features depend on the usage of different W tips, even if prepared following the same procedure and using the same tunneling conditions, suggesting a critical influence of the tip shape