Nanoscopy and Materials Engineering

The strive for unification is a mainspring in natural sciences; perhaps the most famous example is the search for the Unified Field Theory by Einstein, Heisenberg and others that – up to date – has not yet been successful. However, on the comparably modest sublevel of unifying two experimental methods as special tools of spectro-scopy and diffractometry, it may be stated that this aim could be achieved by the undersigned unit leader and coworkers.

The result was the creation of the difference electron nanoscope (DEN) and its application „nanoscopy“ as a comparably new hybrid method – however, the DEN is no classical machine as the term might infer. It is a computer program running on a fast computer system displaying 3D difference electron hyperareas floating in space together with the relevant main physical quantity, the electric field gradient efg, as a wire frame model within the unit cell of the sample under consideration. In this sense, the method acts on a sub-nanometer scale (hence the term „nanoscope“) and delivers images of uncompared symmetrical and physical evidence – letting aside the aesthetical aspects. Has anyone seen a real orbital distribution together with its efg within a crystal before? The following image shows an example.

Barrierefreiheit: Kurzbeschreibung des Bildes

3D difference electron densities (DEDs) (shaded yellow) around the centre position of the FeII-ion (red) with the efg as blue wire frame model in the unit cell of synth. Fe2SiO4. View along the c-direction (space group Pnma); for better spatial impression the surr. O2- octahedron is denoted by green lines, the adjacent silicon-O tetrahedron by yellow ones. Along certain superexchange pathways close to special oxygens, residual DED/magnetic moment densities can be recognized as the theory of magnetism for special solid state materials has predicted

From: Werner Lottermoser: The Difference Electron Nanoscope: Methods and Applications. © 2017 PanStanford Publishing Pte. Ltd., Singapore, Ashford Colour Press Ltd. ISBN 978-981-4774-01-7

 

However, the method is not a purely academic playground. Its application should lead to a better understanding of electric and magnetic interactions in crystals in order to improve the existing technical properties of materials (mat „engineering“) or to derive new compounds with unforeseen features. In this sense, the method fits well in the existing materials research activities of the Department and the Division.

At present, the DEN method consists of the following sub-units, partly available at Salzburg:

  • Classical 57Fe Mössbauer Spectroscopy, in partic. Single Crystal Mössbauer Spectroscopy SCMBS to derive the experimental efg
  • Diffractometry (X-ray, neutron and synchrotron d.) to evaluate the difference electron densities/magnetic electron densities and to derive a semi-empirical efg
  • Density Functional Theory (Self-Consistent-Charge SCC X alpha ­- Method) to determine a full-quantitative efg for comparison and for an important interaction with the experimental team


Why is the efg, obviously, so significant? Many physical and technical quantities have tensor character, i.e. they are dependent on size and direction, like the elastic tensor, the dielectric tensor, magnetic susceptibility a.s.o. - in our case the tensor of the electric field gradient. All these have in common that they are dependent on structural and symmetric properties of the solid state, i.e. the sample under consideration. This means that for a given crystallographic structure determined by the atom/ion positions and given properties like, e.g., piezoelectricity, magnetism, elasticity/plasticity, luminescence, conductivity a.s.o., the careful choice of the ions and their relative arrangement in the solid state let us create „designed“ materials (also nanomaterials).

An example is the synthesis and research on special Li ion conductors with garnet structure (battery research) that were investigated by our team.

 

Last, but not least: the DEN method is not confined to iron containing samples as the application of 57-Fe Mössbauer spectroscopy might infer: An efg can also be derived from NMR/NQR measurements, the DFT is only dependent on the performance of the computer system and diffractometry has no limitations at all. In this sense, the DEN method is rather universal. The „hype“ around it in the preceding years, was, however, merely occurring in foreign countries (USA, China). Werner Lottermoser 

 

  • News
    Tom Rosenstiel, one of the most respected thinkers on the future of the media, will speak on 23 May at 19:00 in HS 380 of the Faculty of Arts and Sciences / Kultur- und Gesellschaftswissenschaftlichen Fakultät (Rudolfskai 42) about the future of democracy in the age of Fake News, the rise of Russian trolls in the Internet and how journalism will look in the future.
    From Eating to Swaddling: Nature determines the rhythm of many youngsters. So that family-friendliness reaches everyone, here is some information on how and where at the University of Salzburg everyday life with small children is easier.
    At the beginning of the 20th Österreichischen Juristentags, a podium discussion will take place on 23 May, 2018, at 18:00 at the University of Salzburg in the series "Rechtspanorama" on "Do Facebook & Co Endanger Democracy?". The organizers are the daily newspaper, Die Presse, and the University of Salzburg.
    From now until 3 July is the registration period for the ditact_women's IT Summer School of the University of Salzburg, which will take place from 20 August to 1 September, 2018, at the Unipark Nonntal and at the Fachhochschule Salzburg.
    Renaud Dehousse is President of the European University Institute, a position held since 1 September, 2016. Before coming to the EUI, he was Professor and Jean Monnet Chair in EU Law and European Policy Studies at Sciences Po Paris from 2005 to 2016, where he founded and directed the Centre d'études européennes.
    The lecture series, Educational Migration Research in a Comparative Perspective, launches on 17 April, 2018, 17:15 - 18:45, HS Thomas Bernhard (Unipark).
    Event series on the 80th anniversary of the burning of books in Salzburg.
  • Veranstaltungen
  • 23.05.18 Polemik zwischen Kunst und Religion bei Luis Buñuel
    24.05.18 Detection of periodicity in functional time series
  • PRESS
  • Uni-Shop
  • University of Salzburg's facebook site University of Salzburg's twitter site University of Salzburg's instagram site University of Salzburg's flickr site University of Salzburg's vimeo site