Order, Disorder, Flexibility, Function

 

Andrew Goodwin

Inorganic Chemistry Laboratory, University of Oxford

 

The existence of internal degrees of freedom in a material is often directly responsible for unusual physical behaviour or some particular functional response. In the case of mechanical degrees of freedom, for example, this behaviour might include negative thermal expansion, negative compressibility, and other elastic anomalies. In the case of magnetic degrees of freedom, the interest is often in the emergent behaviour of collective spin entities (e.g. in spin liquid states). Structural disorder nearly always plays a key role, and the most interesting examples are those in which that disorder is strongly correlated rather than random.

 

This talk will explore the role of geometry in some relevant systems where disorder and/or flexibility are crucial for material function, drawing on studies of molecular frameworks, nanoparticles, ehidden orderf magnets and low-dimensional materials. The general problem of structurally characterising disordered states of matter will form a central part of the talk.

 

Relevant references:

gThe crystallography of correlated disorderh, Nature 521, 303 (2015)

gGiant negative linear compressibility in zinc dicyanoaurateh, Nature Materials 12, 212 (2013)

gHidden order in spin-liquid Gd3Ga5O12h, Science 350, 179 (2015)

gEncoding complexity within supramolecular analogues of frustrated magnetsh, Nature Chemistry (in press)

gDesign of crystal-like aperiodic solids with selective disorder-phonon couplingh, Nature Communications (in press; preprint at arxiv:1508.05909)