Acknowledgements
It is a pleasure to thank Louis Hennet, Stefan Klotz, Henry Fischer, Craig Bull and Matthew Tucker for their valuable assistance and advice. The high-pressure work would not have been possible without the help of Keiron Pizzey, Annalisa Polidori, Ruth Rowlands, Dean Whittaker and Kamil Wezka.
Funding
AZ is supported by a Royal Society-EPSRC Dorothy Hodgkin Research Fellowship.