#
Dr. David O'Regan

Assistant Professor, Physics

## Biography

David's research is dedicated to finding unexpected, innovative ways to transform the accuracy, efficiency, and applicability of theory and simulation software for understanding the material world using quantum mechanics. He is known for his work on simulating, from the electrons up, systems that are both spatially complex (e.g., disordered crystals or molecules) and harbour strong interactions that are beyond the predictive capacity of standard techniques.

David is particularly known for his work on extending and refining the class of methods known as constrained DFT and DFT+U. David is actively involved in the development of linear-scaling density functional theory. Here, he implements and improve corrective approaches such as DFT+U, constrained DFT and DFT+DMFT in addition to researching new Wannierisation and time-propagation (TDDFT) algorithms. David maintains a long-term programme in the development of tractable and user-friendly methods moving beyond Kohn-Sham DFT, via the density-matrix and Green's function, not only for spectra but for energies and their derivatives. He's interested in magnetic and multiple-valence properties, generally, and optical, magneto-optical, and photoemission spectroscopies. A particular focus is placed on these properties as exhibited by transition-metal comprising materials, complexes, and nanostructures.

David completed his PhD at the Cavendish Laboratory, University of Cambridge, in 2011, after which he carried out post-doctoral research first there, and then at the École Polytechnique Fédérale de Lausanne (EPFL). Not much later, in 2014, he came to Trinity College Dublin to launch a research group. David is an Assistant Professor (tenured) in the School of Physics and a CRANN Institute Principal Investigator with an affiliation to the SFI AMBER Research Centre.

David's recent grants and awards include the EPSRC-SFI Joint Funding of Research award, SFI AMBER II Funded Investigator status, an AMBER Director's Fund award, a Trinity Provost's PhD Project award, Irish Research Council postgraduate award mentorship, leadership of a competitively-awarded College infrastructure project, as well as research partnership with industry and sponsorship from Enterprise Ireland and the Royal Irish Academy.

David's current roles include that of Director of Teaching & Learning (Undergraduate), Physics; Chair, School of Physics Teaching & Learning Committee; College Tutor, Member, School Executive Committee; Member, Trinity Undergraduate Studies Committee; Member, School Resumption of Activities Committee; Member, School Athena SWAN Committee, Member, Theoretical Physics Degree Course Committee. In recent years he has served as School of Physics Examinations Coordinator, Chair, School of Physics Resumption of Teaching Steering Committee; CRANN seminar series Convenor, Coordinator of the School of Physics Summer Undergraduate Research Experience (SURE) programme, and as the Theoretical Physics Degree Coordinator in Physics.

## Publications and Further Research Outputs

### Peer-Reviewed Publications

**Almohammed, Sawsan, K. Orhan, Okan, Daly, Sorcha, O'Regan, David D., Rodriguez, Brian J., Casey, Eoin, Rice, James H., Electric Field Tunability of Photoluminescence from a Hybrid Peptide-Plasmonic Metal Microfabricated Chip, JACS Au, 1, (11), 2021, p1987-1995 **

**Zhussupbekov, Kuanysh, Walshe, Killian, Walls, Brian, Ionov, Andrei, Bozhko, Sergei I., Ksenz, Andrei, Mozhchil, Rais N., Zhussupbekova, Ainur, Fleischer, Karsten, Berman, Samuel, Zhilyaev, Ivan, O'Regan, David D., Shvets, Igor V., Surface Modification and Subsequent Fermi Density Enhancement of Bi(111), The Journal of Physical Chemistry C, 125, (10), 2021, p5549-5558 **

**Alotibi S, Hickey BJ, Teobaldi G, Ali M, Barker J, Poli E, O'Regan DD, Ramasse Q, Burnell G, Patchett J, Ciccarelli C, Alyami M, Moorsom T, Cespedes O., Enhanced Spin-Orbit Coupling in Heavy Metals via Molecular Coupling., ACS Applied Materials & Interfaces, 13, (4), 2021, p5228-5234 **

**Kenan Elibol, Clemens Mangler, David D. O'Regan, Kimmo Mustonen, Dominik Eder, Jannik C. Meyer, Jani Kotakoski, Richard G. Hobbs, Toma Susi, and Bernhard C. Bayer, Single Indium Atoms and Few-Atom Indium Clusters Anchored onto Graphene via Silicon Heteroatoms, ACS Nano, 15, (9), 2021, p14373-14383 **

**Prentice J.C.A., Aarons J., Womack J.C., Allen A.E.A., Andrinopoulos L., Anton L., Bell R.A., Bhandari A., Bramley G.A., Charlton R.J., Clements R.J., Cole D.J., Constantinescu G., Corsetti F., Dubois S.M.-M., Duff K.K.B., Escartin J.M., Greco A., Hill Q., Lee L.P., Linscott E., O'Regan D.D., Phipps M.J.S., Ratcliff L.E., Serrano A.R., Tait E.W., Teobaldi G., Vitale V., Yeung N., Zuehlsdorff T.J., Dziedzic J., Haynes P.D., Hine N.D.M., Mostofi A.A., Payne M.C., Skylaris C.-K., The ONETEP linear-scaling density functional theory program, Journal of Chemical Physics, 152, (17), 2020**

**MacEnulty, Lórien, O'Regan, David D., Calculation of the Magnetostatic Energy in Spin Density Functional Theory, Journal of Undergraduate Reports in Physics, 30, (1), 2020, p100005 **

**Roychoudhury S, Sanvito S, O'Regan DD., Neutral excitation density-functional theory: an efficient and variational first-principles method for simulating neutral excitations in molecules., Scientific reports, 10, (1), 2020, p8947 **

**Rangel, T., Del Ben, M., Varsano, D., Antonius, G., Bruneval, F., da Jornada, F.H., van Setten, M.J., Orhan, O.K., O'Regan, D.D., Canning, A., Ferretti, A., Marini, A., Rignanese, G.-M., Deslippe, J., Louie, S.G., Neaton, J.B., Reproducibility in G 0W0 calculations for solids, **

*Computer Physics Communications*, 255, 2020, p107242-

**Orhan, O.K., O'Regan, D.D., First-principles Hubbard U and Hund's J corrected approximate density functional theory predicts an accurate fundamental gap in rutile and anatase TiO2, Physical Review B, 101, (24), 2020, p245137-**

**Almohammed, S., Fularz, A., Zhang, F., Alvarez-Ruiz, D., Bello, F., O'Regan, D.D., Rodriguez, B.J., Rice, J.H., Flexing Piezoelectric Diphenylalanine-Plasmonic Metal Nanocomposites to Increase SERS Signal Strength, ACS Applied Materials and Interfaces, 12, (43), 2020, p48874-48881 **

**Backes C, Campi D, Szydlowska BM, Synnatschke K, Ojala E, Rashvand F, Harvey A, Griffin A, Sofer Z, Marzari N, Coleman JN, O'Regan DD., Equipartition of Energy Defines the Size-Thickness Relationship in Liquid-Exfoliated Nanosheets., ACS Nano, 13, (6), 2019, p7050-7061 **

**Bello, F. and Orhan, O.K. and Abadia, N. and O'Regan, D.D. and Donegan, J.F., Material Characterization and Thermal Performance of Au Alloys in a Thin-Film Plasmonic Waveguide, OSA Technical Digest, CLEO: Applications and Technology 2019,, San Jose, California United States, , 5-10 May, (8749235), 2019, JTu2A.110-**

**Orhan, O.K., O'Regan, D.D., TDDFT+U: A critical assessment of the Hubbard U correction to exchange-correlation kernels and potentials, Physical Review B, 99, (16), 2019**

**Orhan, O.K., O'Regan, D.D., Plasmonic performance of Au xAgyCu1-x-y alloys from many-body perturbation theory, **

*Journal of Physics Condensed Matter*, 31, (31), 2019

**Roychoudhury, S. and O'Regan, D.D. and Sanvito, S., Wannier-function-based constrained DFT with nonorthogonality-correcting Pulay forces in application to the reorganization effects in graphene-adsorbed pentacene, Physical Review B, 97, (20), 2018, p085303-**

**Linda A. Zotti, S. Sanvito, and David D. O'Regan, A simple descriptor for energetics at fcc-bcc metal interfaces, Materials & Design, 142, 2018, p158 - 165**

**Linscott, E.B., Cole, D.J., Payne, M.C., O'Regan, D.D., Role of spin in the calculation of Hubbard U and Hund's J parameters from first principles, Physical Review B, 98, (23), 2018**

**Emilio Artacho and David D. O'Regan, Quantum mechanics in an evolving Hilbert space, Physical Review B, 95, (11), 2017, p5155 **

**Glenn Moynihan, Stefano Sanvito, and David D. O'Regan, Strain-induced Weyl and Dirac states and direct-indirect gap transitions in group-V materials, 2D Materials, 4, (4), 2017, p045018 **

**Glenn Moynihan, Gilberto Teobaldi, and David D. O'Regan, Inapplicability of exact constraints and a minimal two-parameter generalization to the DFT+$U$ based correction of self-interaction error, Physical Review B, 94, (22), 2016, p220104(R) **

** D. D. O'Regan and G. Teobaldi, Optimization of constrained density functional theory, Physical Review B, 94, (3), 2016**

**David H. P. Turban, Gilberto Teobaldi, David D. O'Regan, and Nicholas D. M. Hine, Supercell convergence of charge-transfer energies in pentacene molecular crystals from constrained DFT, Physical Review B, 93, (16), 2016**

**Hanlon D, Backes C, Doherty E, Cucinotta CS, Berner NC, Boland C, Lee K, Harvey A, Lynch P, Gholamvand Z, Zhang S, Wang K, Moynihan G, Pokle A, Ramasse QM, McEvoy N, Blau WJ, Wang J, Abellan G, Hauke F, Hirsch A, Sanvito S, O'Regan DD, Duesberg GS, Nicolosi V, Coleman JN, Liquid exfoliation of solvent-stabilized few-layer black phosphorus for applications beyond electronics., Nature communications, 6, 2015, p8563 **

**Weber C., Cole D.J., O'Regan D.D., Payne M.C., Renormalization of myoglobin-ligand binding energetics by quantum many-body effects, Proceedings of the National Academy of Sciences of the United States of America, 111, (16), 2014, p5790 - 5795, p5790-5795 **

**Weber, C., O'Regan, D.D., Hine, N.D.M., Littlewood, P.B., Kotliar, G., Payne, M.C., Importance of many-body effects in the kernel of hemoglobin for ligand binding, Physical Review Letters, 110, (10), 2013**

**Heiss, M., Fontana, Y., Gustafsson, A., Wüst, G., Magen, C., O'Regan, D.D., Luo, J.W., Ketterer, B., Conesa-Boj, S., Kuhlmann, A.V., Houel, J., Russo-Averchi, E., Morante, J.R., Cantoni, M., Marzari, N., Arbiol, J., Zunger, A., Warburton, R.J., Fontcuberta I Morral, A., Self-assembled quantum dots in a nanowire system for quantum photonics, Nature Materials, 12, (5), 2013, p439-444 **

**Weber, C., O'Regan, D.D., Hine, N.D.M., Payne, M.C., Kotliar, G., Littlewood, P.B., Vanadium dioxide: A Peierls-Mott insulator stable against disorder, Physical Review Letters, 108, (25), 2012**

**O'Regan, David D., Optimised Projections for the Ab Initio Simulation of Large and Strongly Correlated Systems, Springer Berlin Heidelberg, 2012**

**O'Regan, D.D., Hine, N.D.M., Payne, M.C., Mostofi, A.A., Linear-scaling DFT+U with full local orbital optimization, Physical Review B - Condensed Matter and Materials Physics, 85, (8), 2012**

**Cole, D.J., O'Regan, D.D., Payne, M.C., Ligand discrimination in myoglobin from linear-scaling DFT+ U, Journal of Physical Chemistry Letters, 3, (11), 2012, p1448-1452 **

**O'Regan, D.D., Payne, M.C., Mostofi, A.A., Generalized Wannier functions: A comparison of molecular electric dipole polarizabilities, Physical Review B - Condensed Matter and Materials Physics, 85, (19), 2012**

**O'Regan, D.D., Payne, M.C., Mostofi, A.A., Subspace representations in ab initio methods for strongly correlated systems, Physical Review B - Condensed Matter and Materials Physics, 83, (24), 2011**

**O'Regan, D.D., Hine, N.D.M., Payne, M.C., Mostofi, A.A., Projector self-consistent DFT+U using nonorthogonal generalized Wannier functions, Physical Review B - Condensed Matter and Materials Physics, 82, (8), 2010**

### Non-Peer-Reviewed Publications

**L. MacEnulty and D. D. O'Regan, Hubbard U and Hund's Coupling J Parameters from First Principles: Towards accurate Heisenberg exchange coupling parameters for NiO, QUOROM-V, Online, 2021**

**D. Lambert and D. D. O'Regan, Systematic Evaluation of First Principles DFT+U+J Algorithms for the Fast and Accurate Modelling of Transition Metal Oxides, MRS Fall Meeting and Exhibit, Online and Boston, MA, U.S.A., 2021**

**K. Elibol, C. Mangler, D. D. O'Regan, K. Mustonen, D. Eder, J. C. Meyer, J. Kotakoski, R. G. Hobbs, P. A. van Aken, T. Susi, and B. C. Bayer, Self-assembly and heteroatomic anchoring of single indium atoms and few-atom indium clusters on graphene, EUROMAT 2021, Online, 2021**

**D. D. O'Regan, O. K. Orhan, E. B. Linscott, G. Moynihan, and G. Teobaldi, A linear-response approach for first-principles Hund's J parameters: insights, oxides, and self-consistency, APS March Meeting, Online and Chicago, IL, U.S.A., 2021**

**L. MacEnulty and D. D. O'Regan, On using an auxiliary magnetic charge density to calculate the magnetostatic dipole-dipole correction to spin-density functional theory (DFT), EUROMAT 2021, Online, 2021**

**D. P. Gavin and D. D. O'Regan, Quantum-mechanical computational screening and design of resilient plasmonic alloys for ICT and sensing, AMBER ICT Theme Meeting, Trinity College Dublin, IE, 2021**

**Elibol, Kenan, Mangler, Clemens, O'Regan, David D., Mustonen, Kimmo, Eder, Dominik, Meyer, Jannik C., Kotakoski, Jani, Hobbs, Richard G., van Aken, Peter A., Susi, Toma, Bayer, Bernhard C., Single indium atoms and few-atom indium clusters anchored onto graphene via silicon heteroatoms, Microscopy and Microanalysis, 27, (S1), Cambridge University Press , 2021, pp3346-3347 **

**D. D. O'Regan, Force calculations in density-functional theory with extra challenges: Strongly-correlated materials, multi-centre constraints, and time-evolving basis sets, American Chemical Society Fall 2021 National Meeting & Exposition, Online and Atlanta, GA, U.S.A., 2021**

**L. MacEnulty and D. D. O'Regan, Calculation of the Magnetostatic Dipole-Dipole Correction to Periodic Spin-Density Functional Theory Using an Auxiliary Magnetic Charge Density, Materials Research Society (MRS) MRS Spring Meeting and Exhibit, Online, 2021**

**D. D. O'Regan, The partner of the Hubbard U: interpretation of Hund's J in DFT+U methods, linear-response calculations for J, and the results to expect, EPFL THEOS Group & NCCR-MARVEL Seminar, Online and Lausanne, CH, 2021**

**D. D. O'Regan, O. K. Orhan, G. Moynihan, E. B. Linscott, D. J. Cole, and G. Teobaldi, The partner of the Hubbard U: interpretation of Hund's J in DFT+U methods, Psi-k School "Bridging First-Principles Calculations and Effective Hamiltonians", Online, hosted by IIT Genova, IT, 2021**

**K. Elibol, C. Mangler, D. D. O'Regan, K. Mustonen, D. Eder, J. C. Meyer, J. Kotakoski, R. G. Hobbs, T. Susi, and B. C. Bayer, Indium Oligomers anchored via Silicon Heteroatoms onto Graphene, Microscopy Society of Ireland Symposium, Dublin, IE, 2020**

**D. P. Gavin, O. K. Orhan, and D. D. O'Regan, Simulation protocols for paramagnetic transition-metal oxides", Total Energy and Force Methods 2020, Donostia-San Sebastián, ES, 2020**

**S. Roychoudhury, S. Sanvito, and D. D. O'Regan, Neutral Excitation Density Functional Theory, Evolution of Electronic Structure Theory and Experimental Realization, Online, organised by SRM IST KTR (India), IIT Madras (India) and Uppsala University (Sweden), 2020**

**D. P. Gavin, O. K. Orhan, and D. D. O'Regan, Corrective first-principles approaches for paramagnetic transition-metal oxides, Computational School on Electronic Excitations in Novel Materials Using the Yambo Code, Trieste, IT, 2020**

**S. Roychoudhury, D. D. O'Regan, and S. Sanvito, Evaluation of Pulay forces due to change in overlap of subspace-projection orbitals in constrained DFT: Application in calculation of reorganization energy of adsorbed molecule, APS March Meeting, Boston, MA, U.S.A. , 2019**

**D. D. O'Regan, Through thick and thin: A size-thickness power law for liquid-phase exfoliated 2D nanosheets, Materials & Molecular Modelling Hub Conference and User Meeting, University College London, U.K., 2019**

**D. D. O'Regan, Challenges in quantum materials simulation meet challenges in green energy, Dublin University Physical Society, Trinity College Dublin, IE, 2019**

**D. D. O'Regan, G. Moynihan, O. K. Orhan, E. B. Linscott, M. C. Payne, G. Teobaldi, and D. J. Cole, Towards automated self-correction of approximate DFT using first-principles Hubbard U and Hund's J parameters, Electronic Structure Discussion Group, University of Cambridge, Cambridge, U.K., 2019**

**D. D. O'Regan, G. Moynihan, E. B. Linscott, O. K. Orhan, G. Teobaldi, D. J. Cole, M. C. Payne, Towards an automated self-correction protocol for approximate DFT: facile first-principles Hubbard U and Hund's J parameters for arbitrary subspaces, Computational Molecular Science Conference, Warwick, U.K., 2019**

**S. Roychoudhury, D. D. O'Regan, and S. Sanvito, Pulay Forces with Constrained DFT: Calculation of Reorganization Energy, ONETEP Masterclass 2019: Karl Wilkinson Prize talk, Warwick, UK, 2019**

**D. D. O'Regan, An introduction to modern scholarly publication, Trinity Student Scientific Review IV Launch, Trinity College Dublin, IE, 2018**

**K. Walshe, S. Bozhko, B. Walls, K. Zhussupbekov, D. D. O'Regan, and I.V. Shvets, Surface Defects on Cu (111): A combined STM & DFT study, 34th European Conference on Surface Science, Aarhus, DK, 2018**

**D. D. O'Regan, G. Moynihan, O. K. Orhan, E. B. Linscott, M. C. Payne, G. Teobaldi, and D. J. Cole, Self-consistent Hubbard U and Hund's J parameters for DFT from ground-state tracking linear response, New Generation in Strongly Correlated Electrons Systems, Donostia-San Sebastián, ES, 2018**

**S. Roychoudhury, S. Sanvito, and D. D. O'Regan, Excitonic DFT: An Efficient and Flexible Constrained DFT Approach for Simulating Neutral Excitations in Isolated and Periodic Systems, APS March Meeting, Los Angeles, CA, U.S.A., 2018**

**D. D. O'Regan, G. Moynihan, O. K. Orhan, and G. Teobaldi, A self-contained linear-response approach to constrained DFT, DFT+U, and TDDFT+U, EPFL THEOS Group & NCCR-MARVEL Seminar, Lausanne, CH, 2017**

**G. Moynihan, S. Sanvito, and D. D. O'Regan, Strain-induced Weyl and Dirac states and direct- indirect gap transitions in group-V materials, SFI AMBER Centre International Site Review, Dublin, IE, 2017**

**O. K. Orhan and D. D. O'Regan, A Hubbard U based correction method for exciton binding in neutral excitations: TDDFT+U, DPG Spring Meeting, Dresden, DE, 2017**

**E. Linscott, D. Cole, D. O'Regan, C. Weber, and M. Payne, Electronic Correlation in Biology: advances and applications of linear-scaling DFT, DFT+U, and DMFT, Autumn School in Correlated Electrons, Forschungszentrum Jülich, Germany, 2017**

**A. Lunghi, S. Sanvito, and D. D. O'Regan, Towards multi-scale high-throughput calculations of thermal and mechanical properties in transition-metal alloys, DPG Spring Meeting, Dresden, DE, 2017**

**D. D. O'Regan, Developments in linear-scaling DFT for theoretical spectroscopy and Mott- Hubbard physics in disordered systems, Workshop on Research Collaboration FAPESP-Trinity, São Paulo, BR, 2017**

**D. D. O'Regan, G. Moynihan, and G. Teobaldi, "Optimizing constraints and corrections in approximate DFT, 17th International Conference on Density-Functional Theory and its Applications, Tällberg, SE, 2017**

**D. D. O'Regan and N. Marzari, DFT+U(ω): Frequency-dependent Hubbard U correction, Physics Institute, Universidade Federal Fluminense, Niteroí, BR, 2017**

**G. Moynihan, G. Teobaldi, and D. D. O'Regan, An optimisability proof for self-consistent constrained DFT, and its implications for constraint-based self-interaction error correction, DPG Spring Meeting, Dresden, DE, 2017**

**D. D. O'Regan, Hilbert space partitoning and Pulay forces in first-principles simulations using variable basis functions, E-CAM Workshop on Quantum MD, University College Dublin, IE, 2017**

**D. D. O'Regan, G. Moynihan, O. K. Orhan, E. B. Linscott, and G. Teobaldi, A ground-state tracking linear-response method for the self-consistent Hubbard U applied to oxides, coordination complexes, and excitations, Theory and Simulation of Condensed Matter Seminar, King's College London, London, U.K., 2017**

**D. D. O'Regan, G. Moynihan, O. K. Orhan, and G. Teobaldi, Linear-Scaling direct-minimization approaches for orbital-based constrained DFT, DFT+U, and beyond, Chair of Theoretical Chemistry Seminar, TU München, Munich, DE, 2017**

**D. D. O'Regan and E. Artacho, Diffeogeometric compensation for basis set evolution in quantum atomistic simulations, Irish Quantum Foundations Conference, University College Dublin, IE, 2017**

**G. Moynihan, G. Teobaldi, and D. D. O'Regan, The inapplicability of exact constraints, and a minimal two-parameter DFT+U generalisation, for self-interaction error correction, DPG Spring Meeting, Dresden, DE, 2017**

**E. Linscott, D. Cole, D. O'Regan, C. Weber, and M. Payne, Electronic Correlation in Biology: advances and applications of linear-scaling DFT, DFT+U, and DMFT, 5th Annual CCP-BioSim Conference: Frontiers of Biomolecular Simulation, Southampton, U.K., 2017**

**D. D. O'Regan, Quantum-mechanical simulation from the atoms up: opportunities and challenges, Dublin University Physical Society, Dublin, IE, 2016**

**D. D. O'Regan and N. Marzari, DFT+U(ω): Frequency-dependent Hubbard U correction, APS March Meeting, Baltimore, MA, U.S.A., 2016**

**E. Linscott, D. Cole, D. O'Regan, C. Weber, and M. Payne, Describing Correlation Effects in Biological Systems, Physics by the Lake, Windsor, U.K., 2016**

**G. Moynihan, G. Teobaldi, and D. D. O'Regan, Self-consistent calculation of Hubbard U parameters within linear-scaling DFT, APS March Meeting, Baltimore, MA, U.S.A., 2016**

**G. Moynihan and David D. O'Regan, Electronic and Mechanical Properties of Layered Pnictogen Materials, Irish Atomistic Simulators Meeting, University College Dublin, IE, 2016**

**D. D. O'Regan and A. M. Delaney, Investigation of the theory of angular momentum used in the quantum mechanical simulation of magneto-optical spectroscopy, Irish Atomistic Simulators Meeting, University College Dublin, IE, 2016**

**G. Moynihan, G. Teobaldi, and D. D. O'Regan, Comparison of self-consistent DFT+U approaches via direct minimisation, CECAM Workshop: What about U? - Effects of Hubbard Interactions and Hund's Coupling in Solids, Trieste, IT, 2016**

**D. D. O'Regan, Maintaining stability under orbital optimization in linear-scaling DFT: a long- standing problem addressed using differential geometry, CECAM Workshop: Mathematical and Numerical Analysis of Electronic Structure Models, Roscoff, FR, 2016**

**D. D. O'Regan and N. Marzari, Bandwidth renormalization and satellites in SrVO3 from a minimal DFT+U inspired model, ETSF Workshop on Electronic Excitations, Lund, SE, 2016**

**O. K. Orhan and D. D. O'Regan, Towards accurate optical spectra of bulk gold via first-principles methods, Irish Atomistic Simulators Meeting, University College Dublin, IE, 2016**

**E. Linscott, D. Cole, D. O'Regan, C. Weber, and M. Payne, Describing Correlation Effects in Biological Systems, CCP9 Young Researchers Event, York, U.K., 2016**

**D. Cole, G. Lever, L. Lee, C. Weber, D. D. O'Regan, N. Hine, A. Chin, C.-K. Skylaris, and M. Payne, Applications of Large-Scale Electronic Structure Calculations in Biology, Psi-k Conference 2015, Donostia-San Sebastián, ES, 2015**

**D. D. O'Regan and N. Marzari, DFT+U(w): a pragmatic approach for calculating and incorporating dynamical Hubbard U corrections in band-structures and beyond, Materials Theory Group Seminar, Tyndall Institute, Cork, IE, 2015**

**O. K. Orhan and D. D. O'Regan, The optical properties of gold and its alloys via GW and TDDFT, Psi-k Conference 2015, Donostia-San Sebastián, ES, 2015**

**O. K. Orhan and D. D. O'Regan, First-principles simulation of optical spectra in gold-based alloys, International Workshop on Computational Physics and Materials Science, Trieste, IT, 2015**

**D. D. O'Regan and N. Marzari, Frequency-dependent Hubbard U corrections: a viewpoint from density-functional theory, Condensed Matter Theory Group Seminar, University of Warwick, Warwick, UK, 2015**

**G. Moynihan and D. D. O'Regan, Ab Initio Simulation of Enhanced Phosphorus-based Nano-composite Materials, ETSF Young Researchers Meeting, Paris, FR, 2015**

**G. Moynihan and David D. O'Regan, Electronic and Mechanical Properties of Layered Pnictogen Materials, Psi-k Conference 2015, Donostia-San Sebastián, ES, 2015**

**G. Teobaldi, D. D. O`Regan, N. D. Hine, and A. A. Mostofi, Self-consistent projector constrained density functional theory in ONETEP, 249th National Meeting of the American Chemical Society, Denver, CO, U.S.A., 2015**

**David D. O'Regan, 'Notes for users of DFT+U(+J) in ONETEP', 2015, -**

**G. Moynihan and D. D. O'Regan, Ab Initio Simulation of Enhanced Phosphorus-based Nano-composite Materials, International Workshop on Computational Physics and Materials Science, Trieste, IT, 2015**

**E. Linscott, D. Cole, D. O'Regan, N. Hine, and M. Payne, Correlation Effects in the Electronic Structure of PSII, Psi-k Conference 2015, Donostia-San Sebastián, ES , 2015**

**D. D. O'Regan, Revisiting a lesser-known idea of Jules Verne, discussed in his 1889 novel "Sans dessus dessous", Dublin University Physical Society, Dublin, IE, 2014**

**G. Moynihan, C. Cucinotta, S. Sanvito, and D. D. O'Regan, First Principles Simulation of Monolayer Black Phosphorus, Flatlands: Beyond Graphene, Trinity College Dublin, IE, 2014**

**D. D. O'Regan, Large, strongly-correlated systems simulated with linear-scaling DFT: recent developments and applications from oxides to biology, Irish Atomistic Simulators Meeting, Belfast, NI, 2014**

**D. D. O'Regan, Linear-scaling DFT+U and DFT+DMFT or: How I learned to stop worrying and love nonorthogonality, Cecam Workshop: What about U?, Lausanne, CH, 2014**

**G. Teobaldi, B. J. Morgan, D. D. O'Regan, N. D. M. Hine, and A. A. Mostofi, Subspace-corrected functionals for linear-scaling density functional theory simulation of extended energy storage interfaces, 248th National Meeting of the American Chemical Society, San Francisco, CA, U.S.A., 2014**

**G. Moynihan, C. Cucinotta, S. Sanvito, and D. D. O'Regan, First Principles Simulation of Monolayer Black Phosphorus, Hermes Summer School, London, U.K., 2014**

**G. Moynihan, D. O'Regan, C. Cucinotta, and S. Sanvito, Mechanical Properties of Monolayer Black Phosphorus and the effect of van der Waals Forces, ETSF Young Researchers Meeting, Rome, IT, 2014**

**D. D. O'Regan and N. Marzari, Frequency-dependent Hubbard U corrections to DFT beyond the random-phase approximation, Physics at the Nanoscale Seminar, King's College London, U.K., 2014**

**G. Moynihan, D. O'Regan, C. Cucinotta, and S. Sanvito, Mechanical Properties of Monolayer Black Phosphorus and the effect of van der Waals Forces , Irish Atomistic Simulators Meeting, Belfast, NI, 2014**

**G. Teobaldi, D. D. O'Regan, N. D. M. Hine, and A. A. Mostofi, Linear-scaling approaches to charge- and energy-transfer in (extended) photo-electro-chemical interfaces, Donostia International Physics Centre Seminar, Donostia-San Sebastián, ES, 2013**

**D. D. O'Regan, Electronic structure simulations in the large scale and correlated-electron regimes, Molecular Foundry Seminar, Lawrence Berkeley National Laboratory, Berkeley, CA, U.S.A., 2013**

**D. D. O'Regan, Modelling dynamically correlated materials in realistic nanostructures: DFT strategies, and linear-scaling approaches, Collaborative Conference on Materials Research (CCMR), Jeju Island, South Korea, 2013**

**D. D. O'Regan and N. Marzari, Frequency-dependent Hubbard U corrections to DFT: A simple approach, 16th International Workshop on Computational Physics and Materials Science: Total Energy and Force Methods, Trieste, Italy, 2013**

**D. D. O'Regan, (Invited) The O'Regan group in Condensed Matter Theory at TCD School of Physics, SFI AMBER Centre launch event and CRANN Research Day, Dublin, IE, 2013**

**D. D. O'Regan and N. Marzari, Simulating correlated electrons in realistic systems: new approaches, School of Physics Seminar, Trinity College Dublin, IE, 2013**

**D. D. O'Regan and N. Marzari, A new approach to treating dynamically screened interactions in low-energy corrections to density-functional theory, Department of Physics Seminar, University of Fribourg, CH, 2013**

**D. D. O'Regan and N. Marzari, A simplified approach for dynamical Hubbard corrections to DFT, DPG Spring Meeting: Frontiers of Electronic Structure Theory, Regensburg, DE, 2013**

**A. Mostofi, D. D. O'Regan, N. D. M. Hine, and M. C. Payne, Linear-scaling DFT+U applied to hole localization and Friedel oscillations in very dilute (Ga,Mn)As, APS March Meeting, Boston, MA, 2012**

**Y. Fontana, D. D. O'Regan, N. Marzari, A. Fontcuberta i Morral et al., Self-assembled Quantum Dots in Core-Shell Nanowires, NCCR Quantum Science and Technology, Monte Verità, CH, 2012**

**D. D. O'Regan, N. D. M. Hine, M. C. Payne, and A. A. Mostofi, A linear-scaling DFT+U study of Friedel oscillations and localization in very dilute Gallium Manganese Arsenide, DPG Spring Meeting, Berlin, DE, 2012**

**G. Teobaldi, L. J. Hardwick, D. D. O'Regan, N. D. M. Hine, and A. A. Mostofi, Constrained Density Functional Theory in ONETEP, Spring Meeting of the International Society of Electrochemistry, Washington D.C., U.S.A., 2012**

**Cole, D. J., O'Regan, D. D., Lee, L. P., Chau, P. L., Skylaris, C. K., Payne, M. C., Biomolecular simulation with the linear-scaling DFT code ONETEP, Abstracts of papers of the American Chemical Society, 11th International Biorelated Polymer Symposium / 243rd National Spring Meeting of the American-Chemical-Society (ACS), San Diego, CA, U.S.A. , 243, 2012, pp1 **

**D. D. O'Regan, N. D. M. Hine, M. C. Payne, and A. A. Mostofi, A geometrically-motivated approach to optimisation in electronic structure calculations, Numerical Algorithms and High-Performance Computing Group Seminar,, Mathematics Department, EPFL, Lausanne, CH, 2012**

**A. A. Mostofi, D. D. O'Regan, L. Andrinopoulos, N. D. M. Hine, and M. C. Payne, Strong correlations and dispersion interactions with non-orthogonal local orbitals", CECAM Workshop on localised orbitals, Cambridge, UK, 2012**

**C. Weber, D. D. O'Regan, N. D. M. Hine, M. C. Payne, G. Kotliar, and P. B. Littlewood, Dynamical mean-field theory applied to linear scaling density functional theory, CECAM Workshop on localised orbitals, Cambridge, U.K., 2012**

**D. D. O'Regan, S. M.-M. Dubois, P. Umari, and P. D. Haynes(ed.), Efficient localised orbitals for large systems, strong correlations and excitations, Psi-k Newsletter, Cambridge, U.K., 113, Psi-k Organisation, 2012, 11-24 p**

**G. Teobaldi, D. D. O'Regan, N. D. M. Hine, and A. A. Mostofi, Projector self-consistent constrained DFT, CECAM Workshop on localised orbitals, Cambridge, U.K., 2012**

**D. D. O'Regan, Nonorthogonal Wannier function optimisation: geometric aspects and linear-scaling applications to strongly-correlated materials and spectroscopy, DIPC Seminar, University of the Basque Country, Donostia-San Sebastián, ES, 2011**

**D. D. O'Regan, Optimised projections and tensorial invariance in methods for large and strongly-correlated systems, Materials Modelling Laboratory Seminar, Oxford University, Oxford, UK, 2011**

**S. M.-M. Dubois, L. Ratcliff, D.D. O'Regan et al., Prospects for linear scaling calculations beyond DFT accuracy, CECAM Workshop on GW Calculations for Complex Systems, Lausanne, CH, 2011**

**D. D. O'Regan, N. D. M. Hine, M. C. Payne, and A. A. Mostofi, Decorrelating user and theory in ab initio calculations on strongly correlated materials: Projector self-consistent DFT+U for large systems, CECAM Workshop on Materials Informatics, Lausanne, CH, 2011**

**D. D. O'Regan, N. D. M. Hine, M. C. Payne, and A. A. Mostofi, Projector self-consistent DFT+U with linear-scaling and tensorial invariance, CECAM-ACAM Workshop on Density Functional Theory, University College Dublin, IE, 2011**

**D. D. O'Regan, M. C. Payne, and A. A. Mostofi, Linear-scaling and projector self-consistent DFT+U for electronic correlations in large systems, APS March Meeting, Portland, OR, U.S.A., 2010**

** D. D. O'Regan, A. A. Mostofi, and M. C. Payne, Linear-scaling and projector self-consistent DFT+U for electronic correlations in large systems, Thomas Young Centre International Review, University College London, U.K., 2010**

**D. D. O'Regan, A. A. Mostofi, and M. C. Payne, Linear-scaling and projector self-consistent DFT+U for electronic correlations in large systems, Psi-k Conference, Berlin, DE, 2010**

**D. D. O'Regan, Accelerating linear-scaling DFT: Differential geometry meets electronic structure theory, Thomas Young Centre, Imperial College London, U.K., 2010**

** D. D. O'Regan, A. A. Mostofi, and M. C. Payne, Wannier functions in the study of strong electronic correlations in DNA, International Workshop on DNA-based nanotechnology, Max-Planck-Institut für Physik komplexer Systeme, Dresden, DE, 2009**

** D. D. O'Regan, A. A. Mostofi, and M. C. Payne, Linear scaling DFT+U with ONETEP, CCP9 Conference, Cambridge, U.K., 2009**

**D. D. O'Regan, A. A. Mostofi, and M. C. Payne, Linear scaling DFT+U with ONETEP, 14th International Workshop on Computational Physics and Materials Science: Total Energy and Force Methods, Trieste, IT, 2008**