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2nd Joint CCP9-MCC-UKCP-EPCC Workshop on Ab initio Periodic Codes

Daresbury Laboratory, SciTech Daresbury, UK

21-24 January 2019

Supported by:

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Dear participants and code representatives,

Welcome to the 2nd Joint CCP9-MCC-UKCP-EPCC Workshop on Ab initio Periodic Codes!

This workshop is aimed at existing users of periodic codes on high performance compute (HPC) services who wish to:

• Learn to tailor the choice of code to the project, to increase efficient exploitation of HPC

• Explore the capabilities of other codes

• Get more closely connected with the code experts and developers, as well as HPC experts

At this workshop, you will have the chance to perform calculations with a variety of ab initio periodic codes on ARCHER, the UK National Supercomputing Service under the supervision of different periodic codes representatives. Codes represented at the workshop are: ABINIT, BIGDFT, CASTEP, CP2K, CRYSTAL, FHIaims and ONETEP.

Thanks to the hands-on focus of the workshop, you will be able to familiarise yourself with codes by means of tutorials, and begin to apply codes you are not familiar with to your own projects. Tutors will give general presentations on the codes, and offer guidance in the hands-on sessions and one-to-one discussions.

The workshop is organised jointly by the Edinburgh Parallel Computing Centre (EPCC), home of ARCHER and a PRACE Advanced Training Centre, the Collaborative Computational Project for the Study of the Electronic Structure of Condensed Matter (CCP9), and two UK High End Computing Consortia that provide ARCHER computing resources to their members: the Materials Chemistry Consortium (MCC), and the United Kingdom Car Parrinello (UKCP) Consortium.

We hope you will enjoy the workshop.

The organising committee Damian Jones, Gilberto Teobaldi, Esme Williams Daresbury Laboratory, STFC-SCD, UK

Albert Bartók-Pártay, Dominik Jochym Rutherford Appleton Laboratory, STFC-SCD, UK

Andrew Turner Edinburgh Parallel Computing Centre, University of Ediburgh, UK

Venue: Brunner-Mond training suite (A56)

WIFI: Eduroam is available on site and in the training suite but if you are unable to access Eduroam you can request a guest wifi account by completing the form at https://visitorwifi.stfc.ac.uk/. Your STFC sponsor is Gilberto Teobaldi

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Programme Venue: Brunner-Mond training suite (A56) Monday 21 January 12.00-13.00 Registration & lunch 13.00-13.45 Presentation of ABINIT 13.45-14.30 Presentation of FHIaims 14.30-15.15 Presentation of CASTEP 15.15-15.45 Coffee break & Poster Session 15.45-16.30 Presentation of BigDFT 16.30-17.15 Presentation of ONETEP 17.15-18.00 Poster Session Tuesday 22 January 09.00-09.45 Presentation of CRYSTAL 09.45-10.30 Presentation of CP2K 10.30-11.00 Coffee Break & Poster Session 11.00-13.00 Hands on session 13.00-14.00 Lunch 14.00-15.30 Hands on session 15.30-16.00 Coffee Break & Poster Session 16.00-18.00 Hands on session Wednesday 23 January 09.00-9.45 Hands on session 09.45-10.30 ARCHER application talk, Prof Graeme Ackland, Edinburgh 10.30-11.00 Coffee Break & Poster Session 11.00-12.00 Hands on session 12.00-12.45 EPCC talk, Dr Andrew Turner 12.45-14.00 Lunch 14.00-15.30 Hands on session 15.30-16.00 Coffee Break & Poster Session 16.00-17.00 Hands on session 17.00-17.45 ARCHER application talk, Dr Keith McKenna, York Thursday 24 January 09.00-10.30 Hands on session 10.30-10.45 Coffee Break & Collect Posters 10.45-11.50 Hands on session 11.50-12.00 Wrap up and close 12.00- Lunch

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Hydrogen at Extreme Conditions, Alloying Theory and Experiment: The Hecate project Graeme Ackland School of Physics and Astronomy, University of Edinburgh, UK I will discuss our work on the hydrogen phase diagram. These materials are difficult to study experimentally under pressure because of their poor X-ray cross section. For hydrogen in particular, most of the experimental data comes from spectroscopy, a very indirect probe of the structure. Typically, phase transformations can be identified by shifts in the molecular vibrational frequency, but electronic structure calculation is required to identify the structure. A further complication arises because quantum mechanics affects the nuclei, both through zero-point motion and through the indistinguishability of the two atoms in the hydrogen molecule. Even at zero temperature, the molecules in solid hydrogen do not have well-defined orientation. All this means that traditional free energy calculation based on phonons does not work, and a central role in the simulations for molecular dynamics and path integral molecular dynamics. I will review our work on hydrogen simulations across a range of pressures and temperatures, demonstrating the transitions from molecular to atomic phase, from insulator to metal and from solid to liquid.

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UK National HPC facilities and UK national HPC open source benchmarks Andrew R. Turner Edinburgh Parallel Computing Centre, University of Edinburgh, UK Over the past five years there has been a large investment in computational facilities from the UK research councils leading to an unprecedented level of choice for researchers wanting to use computational tools in their research. These include the UK National Supercomputing Service, ARCHER; the UK Research Data Facility; the EPSRC national Tier-2 HPC resources; and the DiRAC STFC national HPC service (as well as several other facilities). These resources provide exciting opportunities for new research but the wide range on offer can lead to confusion on what is available, how to get access to it and how to use it effectively. EPCC has been leading initiatives (including HPC-UK) to help researchers discover what is available, how to get access, and providing support and training to researchers. In this presentation I will give an overview of the facilities available and how to get access to them and an introduction to the open source benchmarking initiative we have been working on to provide information to researchers to help them choose the correct resource for their work.

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Electron trapping in nanocrystalline titanium dioxide Keith McKenna Department of Physics, University of York, UK The trapping of electrons and holes in nanocrystalline oxide materials underpins a diverse range of applications in areas such as solar energy generation, catalysis, gas sensing and nanoelectronics. Directly probing charge trapping in such complex nanocrystalline systems is extremely difficult. Predictive modelling is also challenging due to the self-interaction errors present in widely used exchange-correlation approximations and finite size effects. In this talk I will present some of our recent work aimed at addressing these issues for electrons and hole polarons in the bulk, at surfaces and near interfaces in TiO2. These examples highlight the importance of efficient but accurate methods for modelling charge trapping in order to make reliable predictions. [1] A. R. Elmaslmane, M. B. Watkins and K. P. McKenna, Journal of Chemical Theory and Computation 14, 3740-3751 (2018) [2] A. R. Elmaslmane, J. Wetherell, M. J. P. Hodgson, K. P. McKenna and R. W. Godby, Physical Review Materials 2, 040801(R) (2018) [3] S. Wallace and K. P. McKenna, Journal of Physical Chemistry C 119, 1913 (2015) [4] J. Carey and K. P. McKenna, Journal of Physical Chemistry C 122, 27540 (2018) [5] S. Wallace and K. P. McKenna, Advanced Materials Interfaces 1, 1400078 (2014) [6] K. P. McKenna, Physical Review B 94, 155147 (2016)

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Code representatives ABINIT Prof Gian-Marco Rignanese, Université Catholique de Louvain, Belgium Dr Matteo Giantomassi, Université Catholique de Louvain, Belgium BIGDFT Dr Laura Ratcliff, Imperial College London, UK CASTEP Dr Phil Hasnip, University of York, UK Dr Dominik Jochym, STFC-UKRI, UK Dr Albert Bartók-Pártay, STFC-UKRI, UK CP2K Dr Matthew Watkins, University of Lincoln, UK CRYSTAL Prof Lorenzo Maschio, University of Torino, Italy Dr Silvia Maria Casassa, University of Torino, Italy Dr Barry Searle, STFC-UKRI, UK FHIaims Prof Volker Blum, Duke University, US Dr Sebastian Kokott, Fritz Haber Institute, Germany ONETEP Prof Chris Skylaris, University of Southampton, UK Dr Joseph Prentice, Imperial College London, UK

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List of participants

Abbasi, David King's College London

Ali al-Badri, Mohamed

King's College London

Clayson, Ivan University College London

Cucinotta, Clotilde Imperial College London

Davies, Francis University of Exeter

Davies, Shane University of Exeter

Fowler, Sarah University of Bristol

Guo, Rui University College London

Liu, Yu Yang University of Cambridge

Massillon, Guerda Universidad Nacional Autonoma de Mexico

Mensa, Stefano University of Liverpool

Price, Conor University of Exeter

Sang, Hongqian King's College London

Scivetti, Ivan STFC - UKRI

Taylor, Ned University of Exeter

Wang, Yiyuan Imperial College London

Whalley, Lucy Imperial College London

Youd, Arthur University College London