The FlexMat group's research focuses on understanding and exploiting unusual properties of flexible framework materials. Central to this work is the ability to reveal the atomic structure—how atoms are arranged in 3D space—using crystallography. Knowing the atomic structure allows us to design better materials, and push materials with unique properties towards application.


In our work we make significant use of large-scale national and international neutron and synchrotron X-ray facilities. You can learn more about our research below, explore publications, and read research highlights in the the blog


Andrew Cairns

From 2015–17 Andrew was a postdoctoral scientist at the ESRF,  Europe's brightest X-ray source, based at the high pressure diffraction beamline ID27. Before this he completed both undergraduate and postgraduate studies at the University of Oxford, the latter under the supervision of Prof. Andrew L. Goodwin. In 2016 he received the ESRF Young Scientist Award and PANalytical PCG Thesis Prize from the British Crystallography Association.


Alongside research, Andrew is an advocate for openness and diversity in science. 



Flexibility is something that we encounter in everyday life. Elastic bands are flexible: when stretched the material from which they are made deforms easily. By contrast, some materials are extremely inflexible. What determines if a material is flexible is how the building blocks making up the material are arranged and held together. My research aims to make, understand and apply structural flexibility in a class of materials known as coordination polymers. 

A key goal of my research is to find and characterise flexible materials with very unusual structures or mechanical properties. One such unusual property is negative linear compressibility (NLC). This occurs when, under uniform pressure, a material actually expands along one or more directions during the process of densification, like a folding wine-rack. As rare as it is counterintuitive, such "negative compressibility" behaviour might have application in the design of ultra-sensitive pressure sensors, “smart” responsive devices, artificial muscles and actuators.

This, and other, unusual behaviours arise because of structural topology—how building blocks are arranged. So, for example, the model auxetic structure in this demonstration video has a specific topology that means it expands as it is stretched. As a materials chemist my aim is to design these counterintuitive properties on the atomic scale. I do this using coordination polymers—scaffold-like hybrid materials synthesised by self-assembly of cationic metal nodes with anionic molecular linkers in one, two or three-dimensions.

As a crystallographer I use in-situ diffraction techniques to reveal structural features that give rise to these unusual properties. My research makes use of variable-pressure and variable-temperature single crystal and powder X-ray or neutron diffraction. Large scale national and international research facilities—such as those that produce brilliant synchrotron light or pulsed beams of neutrons—offer unique access to experiments that reveal unprecedented atomic detail using diffraction, but also a range of other techniques including EXAFS, SANS and spectroscopic measurements that can help aid our understanding of a material's properties. 



publication highlights


High-pressure behaviour of Prussian blue analogues: interplay of hydration, Jahn-Teller distortions and vacancies

H. L. B. Boström, I. E. Collings, A. B. Cairns, C. P. Romao and A.L. Goodwin

Dalton Transactions 48, 1647-1655 (2019)

LinkChemRxiv⎜doi: 10.1039/C8DT04463E

Encoding complexity within supramolecular analogues of frustrated magnets

A. B. Cairns, M. J. Cliffe, J. A. M. Paddison, D. Daisenberger, M. G. Tucker, F.-X. Coudert and A.L. Goodwin

Nature Chemistry 8, 442–447 (2016)

LinkarXiv⎜doi: 10.1038/nchem.2462

Design of crystal-like aperiodic solids with selective disorder-phonon coupling

A. R. Overy, A. B. Cairns, M. J. Cliffe, M. G. Tucker and A. L. Goodwin

Nature Communications 7, 10445 (2016)

LinkPDF⎜doi: 10.1038/ncomms10445

Negative linear compressibility

A. B. Cairns and A. L. Goodwin

Physical Chemistry Chemical Physics 17, 20449–20465 (2015, cover article)

Link ⎜arXiv⎜doi: 10.1039/C5CP00442J 

Giant negative linear compressibility in zinc dicyanoaurate

A. B. Cairns, J. Catafesta, C. Levelut, J. Rouquette, A. van der Lee, L. Peters, A. L. Thompson, V. Dmitriev, J. Haines and A. L. Goodwin

Nature Materials 12, 212–216 (2013) 

LinkPDFORA⎜doi: 10.1038/nmat3551



October 23, 2019

The special issue of Molecules "High–Pressure Behaviour of Solids: From Molecular Species to 3D-Framework Materials" is now online!

This Special Issue of Molecules aims to cover a broad range of high-pressure investigations on molecular up to three-dimensional framework...

October 1, 2019

Congratulations to Muzi and Mingze, this year's MSc students in the group who both received distinction marks in their research projects! Muzi's project investigated local structure in chain cyanides and Mingze worked on group 11 pseudo-cyanides. 

I look forward to seei...

In the 2D "flatlands", graphene stands tall as the most exciting discovery for future technologies. Despite its many attractive properties however, graphene lacks a natural band gap that would allow electrical flow to be switched on and off (it is a zero gap semiconduc...

February 25, 2016

In science frustration can become part of everyday life: the experiment doesn't work the way you wanted, someone else booked the instrument you needed, and of course the fact the paper (or your thesis) won't write itself. Most people try to avoid frustration; it is gen...

August 20, 2013

Just like a water bottle shrinks at the end of a flight as the air pressure increases, most objects get smaller in every direction when pressure is applied equally (hydrostatically) around it. Negative linear compressibility (NLC) is the bizarre phenomenon that involve...

July 18, 2013

Andrew Cairns and Ines Collings, DPhil students in the Goodwin Group, explain how they make single crystals in the lab and study their unusual properties.

By showing how to break the rules governing 'normal' materials, this research could lead to the design of brand new...

July 21, 2011

Just as we expect materials to expand on increasing temperature, so too is it our intuition that materials should shrink under pressure. The opposite effect — expansion when pressure is applied —  is termed negative linear compressibility (NLC) and has only recently be...

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Andrew Cairns | Department of Materials, Imperial College London
a.cairns [at] imperial.ac.uk | +44 (0)20 7594 9528