9 Nov 2016: Peter Harrowell

Wed 9 Nov 2016 – 2:30*pm (Murdoch University, Senate Room)

Rethinking Structure in Amorphous Materials: From Geometry to Statistics

Peter Harrowell — School of Chemistry, University of Sydney

Despite a long history, there remain many important open questions about, not just the best description of structure in liquids and glasses, but what use these structures provide in terms of understanding the properties of amorphous materials. This talk will introduce the basic questions concerning the role of structure in materials science, how that structure is characterised and then present recent results on how the geometry of the locally stable structures in an amorphous materials influence the stability of the material with respect to crystallization.2016_11_10_peterharrowell_imageA central conclusion of this research is that advances in the study of amorphous structure will involve abandoning the traditional descriptive geometrical approach to structure in favour of regarding structure in terms of the statistical correlations between local structural elements. It is hoped that the description of this exciting open problem will be both accessible to and of interest for mathematicians.

(* Peter’s talk will be at 4pm, but is part of a mini-workshop that starts at 2:30 *)

9 Nov 2016: Julian Gale

Wed 9 Nov 2016 – 2:30pm (Murdoch University, Senate Room)

Exploring the Nucleation of Biominerals: When Hard Rocks Meet Soft Matter

Paolo Raiteri, Raffaella Demichelis, Wen Zhao, Kasia Koziara, Alicia Schuitemaker and Julian D. Gale

Curtin Institute for Computation/The Institute for Geoscience Research (TIGeR), Department of Chemistry, Curtin University, PO Box U1987, Perth, WA 6845

2016_11_10_juliangale_imageThe nucleation of minerals from ions in aqueous solution underpins important processes from biomineralisation to scale formation and carbon sequestration. All this begins with ion pairing, but what happens next is still a matter that is hotly debated for systems such as calcium carbonate, where the classical nature of nucleation has been called into question [1,2,3]. Therefore it is vital to use both experiment and simulation to fill in the missing details as to how crystalline minerals form. In this presentation we will examine the possible pathways by which two common biominerals, calcium carbonate and calcium oxalate, nucleate in order to try to explain how proteins may influence and control this process. Based on simulation results it will be demonstrated that hard rocks and soft matter are perhaps not as different as they might seem during their earlier stages of formation.


[1] D. Gebauer, A. Völkel, H. Cölfen, Science, 322, 1819 (2008).

[2] R. Demichelis, P. Raiteri, J.D. Gale, D. Quigley, D. Gebauer, Nature Comm., 2, 590 (2011).

[3] A.F. Wallace, L.O. Hedges, A. Fernandez-Martinez, P. Raiteri, J.D. Gale, G.A. Waychunas, S. Whitelam, J.F. Banfield and J.J. De Yoreo, Science, 341, 885-889 (2013)

6 Oct 2016 : Sandy Peterhaensel

Detection of nanometer size differences through human color vision

Speaker : Sandy Peterhänsel, Stuttgart University

Venue    : Thu 6 Oct 2016, 3pm (Murdoch University, Senate Room)

We study how accurately a naked human eye can determine the thickness of thin films and the geometric parameters (height and width) of optical gratings from the observed color. Our approach is based on color-matching experiments, where a sample with unknown parameters is observed next to a reference field of same size. The study of the limits of color discrimination and their dependence
on surrounding conditions for human eyes are one of the major trends in color science [1]. For thin lms this is done by placing the  sample in direct contact to a LCD display, see Fig. 1. For matching of gratings the setup is more complex, as shown in gure 2. This is due to the fact, that only the zeroth order should be observed, as higher orders will lead to an angular dispersion of the wavelengths present in the spectrum of the light source.

In both cases, the color of the reference field is matched by several test persons. From their selection the geometric properties of the thin films, as well as of the gratings are reconstructed via rigorous simulation. We found that the human color observation provides an extremely accurate evaluation of the lm thickness and is comparable to sophisticated instrumental methods in this case. Even for the more complex reconstruction of the grating parameters an accuracy in the range of much more sophisticated methods like scanning  electron microscopy could be observed. Our results suggest that for a wide range of structures, the  color observation may help to get quick, but still accurate, results, without any sophisticated instrumentation.
[1] R.G. Kuehni, Color Res. Appl. 33(324), (2008).
[2] S. Peterhänsel, H. Laamanen, J. Letholahti, M. Kuittinen, W. Osten and J. Tervo, Optica 2(7), (2015)
[3] S. Peterhänsel, H. Laamanen, M. Kuittinen, J. Turunen, C. Pruss, W. Osten and J. Tervo, Opt. Lett. 39(3547), (2014)