Patrick: Influence and Inspiration Rob Jackson Lennard-Jones Laboratories School of Physical & Geographical Sciences Keele University Keele, Staffordshire ST5 5BG, UK 1 Advances in the Chemistry of Disordered Solids: UCL 13/09/2013

Plan of talk Influence – conferences and meetings – textbooks Inspiration – My research and Patrick’s influence on it 2 Advances in the Chemistry of Disordered Solids: UCL 13/09/2013

EURODIM/ICDIM Conferences Patrick was very influential as a member of the international advisory committee of the EURODIM/LATDIC/ICDIM series of conferences. He was at the first one I attended, in Dublin (1982), and the last one he attended was the one I organised at Keele in 1998 (as well as most of those in between). Advances in the Chemistry of Disordered Solids: UCL 13/09/2013 3

Organising committee for ‘LATDIC82’ (photo: UCD 1981) Advances in the Chemistry of Disordered Solids: UCL 13/09/2013 4

ICDIM1988 & EURODIM98 Parma & Keele Advances in the Chemistry of Disordered Solids: UCL 13/09/2013 5

London (Ontario): ‘Retirement’ Symposium: Sept Advances in the Chemistry of Disordered Solids: UCL 13/09/2013 6

UWO symposium programme – morning Advances in the Chemistry of Disordered Solids: UCL 13/09/2013 7

UWO symposium programme – afternoon Advances in the Chemistry of Disordered Solids: UCL 13/09/2013 8

Photos from London (Ontario) September 1989 Advances in the Chemistry of Disordered Solids: UCL 13/09/ Four wise gentlemen

Photos from London (Ontario) September 1989 Advances in the Chemistry of Disordered Solids: UCL 13/09/ With Roger Baetzold, Richard C & Yen Tan

Photos from London (Ontario) September 1989 Advances in the Chemistry of Disordered Solids: UCL 13/09/ With Yen Tan & Sean Corish

Photos from London (Ontario) September 1989 Advances in the Chemistry of Disordered Solids: UCL 13/09/ Alastair Cormack snaps away

Photos from London (Ontario) September 1989 Advances in the Chemistry of Disordered Solids: UCL 13/09/ With Bill Meath

Mansfield College meetings Advances in the Chemistry of Disordered Solids: UCL 13/09/ Patrick regularly attended the Mansfield College meetings, organised by Richard Catlow, including this one, in Who else can you recognise in the photo? A later meeting was organised to mark his retirement, but I don’t have a photo for that!

Influence: Keele Although I first met Patrick when I was a postdoc at UCL in the early 1980s, it was really at Keele in 1986 when I first worked with him. He visited Keele from 17 August for 2 weeks, with Sean, Roger Baetzold and Yen Tan; the visit which famously included the Bank Holiday weekend, terrible weather, and the ‘second worst day’ of Patrick’s life... Advances in the Chemistry of Disordered Solids: UCL 13/09/

Keele: August 1986 In 1986 the development of photographic film was still a topic of commercial importance, and Patrick, Sean, Roger and Yen were trying to improve the existing potentials for the silver halides. My small part in this story was showing Patrick how to use CASCADE (based on HADES, and which preceded GULP). Advances in the Chemistry of Disordered Solids: UCL 13/09/

Silver halides modelling Advances in the Chemistry of Disordered Solids: UCL 13/09/

The paper itself … Advances in the Chemistry of Disordered Solids: UCL 13/09/

Influence: Textbooks Since retirement, Patrick has written two textbooks: Advances in the Chemistry of Disordered Solids: UCL 13/09/ ‘Group Theory with Applications in Chemical Physics’ (2005) ‘Thermodynamics’ (May 2013)

Research inspiration Advice offered by PWMJ: – (Your research plan) must be realistic, but should bring out the fact that you have plenty of ideas and will be able to develop an active research programme which will involve not only yourself but future graduate students. – This was very useful to me as I began my career, and I have tried to continue to follow it ever since. Advances in the Chemistry of Disordered Solids: UCL 13/09/

My recent research We are interested in using computer modelling to assist in the understanding, design and optimisation of new materials for specific applications. Applications of current interest are in optical devices, and materials relevant to nuclear energy generation. I will focus on four areas. Advances in the Chemistry of Disordered Solids: UCL 13/09/

1. Modelling nuclear fuels My original postdoc contract at UCL was to model fission gases in UO 2. This culminated in a publication in 1986 which reported a new potential for this material. As a result of the renewed interest in nuclear energy, and a research collaboration with Mark Read, it seemed appropriate to revisit the modelling of UO 2 and other actinide oxides: Advances in the Chemistry of Disordered Solids: UCL 13/09/

Advances in the Chemistry of Disordered Solids: UCL 13/09/ Journal of Nuclear Materials 406, (2010)

How good is the final fit? (More details in paper) ParameterCalc.Obs. %% ParameterCalc.Obs. %% Lattice Constant [Å] C 11 [GPa] U 4+ – U 4+ Separation [Å] C 12 [GPa] U 4+ – O 2- Separation [Å] C 44 [GPa] O 2- – O 2- Separation [Å] Bulk Modulus [GPa] Static Dielectric Constant High Frequency Dielectric Constant Advances in the Chemistry of Disordered Solids: UCL 13/09/2013 Note that it is unusual to have this amount of data to fit to!

Latest work on nuclear fuels The potential has been used to calculate the defect properties of UO 2 A similar procedure has been applied to PuO 2 and mixed oxide (MOX) fuel has been modelled (funded through a PhD studentship from AWE). The next slide shows some recent work from Scott Walker. On an interesting note, most other current work on UO 2 is being done using DFT! Advances in the Chemistry of Disordered Solids: UCL 13/09/

The MOX system UO 2 /PuO 2 was modelled for a range of Pu concentrations allowing the variation of lattice parameter with Pu concentration to be predicted. As expected, lattice parameter decreases linearly with increasing Pu concentration. Modelling MOX fuel From: S R Walker, PhD thesis (in preparation) Advances in the Chemistry of Disordered Solids: UCL 13/09/201326

2. Modelling materials for nuclear clock applications 229 Th is being investigated for use in ‘nuclear clocks’; its first nuclear excited state is only ~ 8 eV above the ground state, and can be probed by VUV radiation. Nuclear clocks promise up to 6 orders of magnitude improvement in precision over next generation atomic clocks, as well as enhanced stability. Th has to be doped into a suitable crystal: CaF 2 and LiCaAlF 6 /LiSrAlF 6 are being tested. Advances in the Chemistry of Disordered Solids: UCL 13/09/

Journal of Physics: Condensed Matter 21, (2009) Advances in the Chemistry of Disordered Solids: UCL 13/09/

Summary of nuclear clocks project In all 3 materials the Th 4+ ion is predicted to dope at the 2+ site (Ca 2+ or Sr 2+ ) with charge compensation by formation of F - interstitials. DFT calculations have been carried out which show that the presence of the defects does not affect the band gap of the material. Crystals are being grown (using the cheaper 232 isotope initially). Advances in the Chemistry of Disordered Solids: UCL 13/09/

232 Th doped CaF 2 Advances in the Chemistry of Disordered Solids: UCL 13/09/ Green because of the colour of the laser pointer!

Other active areas 3. Modelling of optical materials – Here mixed metal fluorides are modelled, doped with rare earths, to determine the dopant location and effect on crystal morphology. 4. Modelling of lithium niobate – We revisited this material (following the Donnerberg work in the 1980s) and derived a new potential. LiNbO 3 is still of interest (conference in Germany next week!) Advances in the Chemistry of Disordered Solids: UCL 13/09/

Some of those who couldn’t attend but sent messages/apologies John Vail (letter on next slide) Roger Baetzold (‘will be there in spirit’) Darrell Comins David Smith Bud Bridges Miguel Moreno Wyn Roberts Peter Sushko Martin Nikl Mário Valerio Bill Meath Neil Allan Alan Lidiard Advances in the Chemistry of Disordered Solids: UCL 13/09/

33 “Dear Rob, Thanks for the notice of the Patrick Jacobs memorial symposium. Although I am in reasonably good health and able to continue with research, my medical condition is not sufficiently stable to get health insurance for a trip abroad. Please convey the following message to our mutual colleagues who attend. I met Patrick Jacobs through our mutual involvement with Theoretical Physics Division at Harwell. It was immediately evident that he was truly “a scholar and a gentleman.” We in Canada were fortunate to have shared his second career in London, Ontario. I was well aware of his first career in London, England. To my knowledge, his contributions to the understanding of atomic diffusion and optical properties of solids and their defects were particularly notable. I was fortunate to attend his retirement symposium at the University of Western Ontario. I was also present in Riga when his wife Rita suffered a stroke that led to her death. It was sad beyond my ability to describe. I wish that I could be with our many friends on this occasion to renew our contacts and to celebrate Patrick’s memory. I send particular greeting to Richard Catlow, Sean Corish, Eugene Kotomin and yourself, Rob Jackson. There will no doubt be others there whose acquaintance I equally cherish. Some of you may be interested to know that I continue with the Harwell legacy in Canada by my research: “Electron density waves having the grapheme structure.” All Hail, John Vail.”

Conclusions Patrick had a considerable impact on my career. His interest in my work and friendly advice was always appreciated. I hope the special journal issue being planned is a fitting tribute to his many contributions to our field. Thanks for attending, and I hope you are enjoying the symposium. Advances in the Chemistry of Disordered Solids: UCL 13/09/