Transparencies of talks

presented by Matthias Scheffler

HITS Colloquium Matthias Scheffler on Making the Data Revolution Happen

2018, July 23
HITS Colloquium, Heidelberg

Big-Data Analytics for Materials Science: Concepts, Challenges, and Hype

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2015, October 20
Xingda Lecture, Beijing

Plenary talk at the DPG Spring Meeting

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2012, March 30

Present status of ab initio electronic structure calculations

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2001, July 23
Harnack-Haus, Berlin

In this talk I will sketch the "ab initio line" of the field often called "Computational Sciences and Engineering", that at present is significantly increasing in importance and impact. To predict materials properties starting from the electronic structure and going all the way to technically relevant time and length scales, is a desire that has existed for many years in particular in condensed-matter physics, materials science, chemistry, and bio-chemistry. However, only recent, spectacular developments in methodology, and the availability of fast computers, enable us now to approach this goal. I will emphasize how density-functional theory calculations can and should be combined with methods from statistical mechanics, meso-/macroscopic continuum mechanics, and thermo-dynamics, and I will demonstrate the value of such studies using selected examples. These examples include:

  • phase transitions of crystals with relevance to mineralogy and geophysics,
  • predictions and description of the function of materials surfaces (e.g., atomic structure, chemical activity),
  • excited states, core-level spectroscopy (many-electron effects), etc.,
  • crystal growth and self-assembly of nano structures, insights into the nature of interactions in biological molecules.

Emphasis will be placed on methodology, simple physical models, concepts, and the development of understanding.

Surface diffusion, growth, and self-assembly of quantum dots at III-V semiconductor surfaces

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1999, June 31
Talk given at VIII-th Symposium on Surface Physics, June 28th - July 2nd, 1999, Trest Castle, Czech Republic.

Surfactants, Diffusion, and Reactivity of GaN Surfaces

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1998, December 2
Talk given at the MRS Meeting, December 1998 in Boston.

Stoichiomery, Structure, and Electronic Properties of Fe_2O_3 (Hematite) (0001)

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1998, March 19
Talk given at the APS March Meeting, March 1998 in Los Angeles.

See also: X.-G. Wang, et al., The hematite (Alpha-Fe2O3)(0001) surface: Evidence for domains of distinct chemistry. Phys. Rev. Lett. 81, 1038 (1998).

Clean and As-covered GaN Surfaces: Cation-Stabilized Structures and Surfactant behavior

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1998, March 15
Talk given at the APS March Meeting, March 1998 in Los Angeles.

See also: J. Neugebauer, et al., Clean and As-covered zinc-blende GaN (001) surfaces: Novel surface structures and surfactant behavior. Phys. Rev. Lett. 80, 3097-3100 (1998).

The Role of Quantum Effects and Statistics in Chemical Reactions at Surfaces

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1997 December 18
Plenary talk at the Condensed Matter and Materials Physics Conference of the Insitute of Physics, Exeter, December 1997.

Abstract: The chemistry at surfaces plays a significant role in our daily life; examples are corrosion, lubrication, and heterogenous catalysis. It should be well known (although typically it is ignored) that a proper description of chemical reactions at surfaces ought to consider three key aspects:

  1. A good-quality description of the electronic structure and inter-atomic interactions, i.e., of the high-dimensional POTENTIAL-ENERGY SURFACE experienced by the nuclei. The best approach for this purpose is density-functional theory.
  2. An appropriate description of the DYNAMICS of the nuclei. For reactions involving hydrogen this requires a quantum treatment of the nuclei, in order to account e.g. for zero-point vibrations and tunneling.

A proper treatment of the STATISTICS. Recent calculations revealed that the high dimensionality of phase space requires to consider thousands of trajectories. Typically only about a dozen trajectories have been considered in the past. New methodological developments [1] enable calculations which treat all three aspects.

  • For some specific examples, e.g. the catalytic reactivity of transition metal
  • the poisoning of the catalytic reactivity by adsorbed sulphur

I will discuss and demonstrate the relevance of all three aspects and summarize the modern understanding of chemical properties of surfaces.

[1] A. Gross and M. Scheffler, J. Vac. Sci. Technol. A 15, 1624 (1997); and Phys. Rev. B 57, 2493 (1998)


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