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Dr. David O'Regan
Assistant Professor, Physics

Biography

I am an Assistant Professor in the School of Physics, where I currently serve as the Director of Teaching and Learning (Undergraduate), with an affiliation to CRANN. I am a SFI Principal Investigator and also an SFI Funded Investigator within the AMBER research centre. My research concerns development and innovation in the accurate and computationally increasingly routine quantum-mechanical description of the material world, specifically practical electronic structure simulation for solid state and molecular systems, together with theory and technique development in condensed matter physics and quantum materials discovery. I place an emphasis on materials for ICT and renewable energy. I also have a complementary long-term research interest in more abstract corrective functional development in density functional theory and in many-body theoretical spectroscopy methods. These activities take my Group and I from applications in novel magnets, complex oxides and metallic surfaces, and through to novel two-dimensional materials where we specialise in mechanics calculations, where in each case we enjoy working closely with many experimentalist partners overseas and closer to home.

I completed my PhD at the Cavendish Laboratory, University of Cambridge in 2011, after which I carried out post-doctoral research first there, and then at the École Polytechnique Fédérale de Lausanne (EPFL). Since arriving to Trinity I have served in Physics over different periods as Director of Examinations, Assistant DUTL, and Theoretical Physics Degree Course Coordinator, and in recent years have managed the School's summer research internship programme. At CRANN and AMBER, I organised for a successful seminar series for PostDocs and PhD students, and I continue to participate in a number of international applied research projects.

Publications and Further Research Outputs

Peer-Reviewed Publications

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 Journal Article, 2021 DOI

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 Journal Article, 2021 DOI

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 Journal Article, 2021 DOI

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 Journal Article, 2021

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 G0W0 calculations for solids, Computer Physics Communications, 255, 2020, p107242- Journal Article, 2020 DOI

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- Journal Article, 2020 DOI

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 Journal Article, 2020 DOI

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 Journal Article, 2020 DOI TARA - Full Text

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 Journal Article, 2020 DOI

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 Journal Article, 2020 DOI

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- Conference Paper, 2019 URL DOI

Orhan, O.K., O'Regan, D.D., Plasmonic performance of AuxAgyCu1-x-y alloys from many-body perturbation theory, Journal of Physics Condensed Matter, 31, (31), 2019 Journal Article, 2019 DOI

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 Journal Article, 2019 DOI TARA - Full Text

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 Journal Article, 2019 DOI

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 Journal Article, 2018 DOI

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 Journal Article, 2018 DOI

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- Journal Article, 2018 TARA - Full Text DOI

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

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 Journal Article, 2017 TARA - Full Text DOI

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

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 Journal Article, 2016 DOI

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) Journal Article, 2016 DOI

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 Journal Article, 2015 TARA - Full Text DOI

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 Journal Article, 2014

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 Journal Article, 2013 DOI URL

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 Journal Article, 2013 URL DOI

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 Journal Article, 2012 DOI URL

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 Journal Article, 2012 DOI URL

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 Journal Article, 2012 URL DOI

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

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 Journal Article, 2012 DOI URL

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 Journal Article, 2011 DOI URL

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 Journal Article, 2010 URL DOI

Non-Peer-Reviewed Publications

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 Oral Presentation, 2021 URL

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 Poster, 2021 URL

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 Published Abstract, 2021 DOI

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

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 Oral Presentation, 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 Oral Presentation, 2021 URL

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 Oral Presentation, 2021 URL

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 Oral Presentation, 2021 URL

Daniel S Lambert, David D O'Regan, DFT+U+J with linear response parameters predicts non-magnetic oxide band gaps with hybrid-functional accuracy, 2021 Working Paper, 2021 URL

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 Oral Presentation, 2021 URL

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 Invited Talk, 2021 URL

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 Poster, 2021 URL

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 Oral Presentation, 2020 URL

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 Oral Presentation, 2020 URL

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 Poster, 2020 URL

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 Poster, 2020 URL

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 Invited Talk, 2019 URL

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 Invited Talk, 2019 URL

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 Invited Talk, 2019 URL

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 Oral Presentation, 2019 URL

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 Invited Talk, 2019 URL

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

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 Oral Presentation, 2018 URL

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

K. Walshe, S. Bozhko, B. Walls, K. Zhussupbekov, D. D. O'Regan, and I.V. Shvets New Generation in Strongly Correlated Electrons Systems Sept. 5 | Donostia-San Sebastián, ES | | "Self-consistent Hubbard U and Hund's J parameters for DFT from ground-state tracking linear response", Surface Defects on Cu (111): A combined STM & DFT study, 34th European Conference on Surface Science, Aarhus, DK, 2018 Oral Presentation, 2018 URL

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 Invited Talk, 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 Poster, 2017 URL

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

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 Oral Presentation, 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 Poster, 2017 URL

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 Oral Presentation, 2017 URL

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 Invited Talk, 2017 URL

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 Oral Presentation, 2017 URL

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 Poster, 2017 URL

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 Poster, 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 Oral Presentation, 2017 URL

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 Invited Talk, 2017

G. Moynihan, G. Teobaldi, D. D. O'Regan, A self-consistent ground-state formulation of the first-principles Hubbard U parameter validated on one-electron self-interaction error, 2017 Working Paper, 2017 URL

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 Oral Presentation, 2017 URL

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 Invited Talk, 2017 URL

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 Poster, 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 Oral Presentation, 2016 URL

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 Oral Presentation, 2016 URL

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 Oral Presentation, 2016 URL

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 Poster, 2016 URL

D. D. O'Regan, Quantum-mechanical simulation from the atoms up: opportunities and challenges, Dublin University Physical Society, Dublin, IE, 2016 Invited Talk, 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 Poster, 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 Oral Presentation, 2016 URL

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

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 Poster, 2016 URL

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 Oral Presentation, 2016 URL

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 Invited Talk, 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 Poster, 2015 URL

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 Poster, 2015 URL

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 Invited Talk, 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 Poster, 2015 URL

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 Poster, 2015 URL

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 Invited Talk, 2015 URL

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

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

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 Oral Presentation, 2015 URL

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 Poster, 2015 URL

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 Invited Talk, 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 Oral Presentation, 2014 URL

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 Poster, 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 Poster, 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 Poster, 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 Oral Presentation, 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 Invited Talk, 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 Invited Talk, 2014 URL

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 Poster, 2014

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

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 Invited Talk, 2013 URL

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 Oral Presentation, 2013 URL

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 Invited Talk, 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 Oral Presentation, 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 Oral Presentation, 2012 URL

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 Oral Presentation, 2012 URL

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 Oral Presentation, 2012 URL

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 Proceedings of a Conference, 2012 URL

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 Oral Presentation, 2012 URL

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 Oral Presentation, 2012 URL

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 Invited Talk, 2011 URL

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 Invited Talk, 2011

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 Invited Talk, 2011 URL

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 Oral Presentation, 2010 URL

Research Expertise

Keywords

Advanced electronic materials; ATOMISTIC SIMULATION; BIOSCIENCE; CHIROPTICAL SPECTROSCOPY; COMPUTER MODELING AND SIMULATION; CONSTRAINED DENSITY-FUNCTIONAL THEORY; DENSITY-FUNCTIONAL THEORY; DYNAMICAL MEAN-FIELD THEORY; Functional Materials; HARD MAGNETIC MATERIALS; LINEAR-SCALING DENSITY-FUNCTIONAL THEORY; MAGNETIC MATERIALS; MANY-BODY PERTURBATION THEORY; MANY-BODY THEORY; MATERIALS SCIENCE; METALLOPROTEINS; nanoscience; Organometallic Chemistry; REDUCED DENSITY-MATRIX FUNCTIONAL THEORY; SEMICONDUCTOR DEVICES AND MATERIALS; Theoretical Physics; THEORETICAL SPECTROSCOPY; TIME-DEPENDENT DENSITY-FUNCTIONAL THEORY

Recognition

Awards and Honours

SFI-EPSRC Principal Investigator 2019

Provost's PhD Project Award 2019-20 (proposal ranked #1) 2019

SFI AMBER II Centre Funded Investigator (competitive) 2017

SFI Research Infrastructure Programme, internal award (competitive) 2017

SFI AMBER I Centre Director's Fund Award (competitive) 2018

President, Dublin University Physical Society 2015-16 2015

European Science Foundation (Psi-k2) workshop coordination award 2012

Springer Thesis Award (Recognizing Outstanding Ph.D. Research) 2011

EPSRC Postdoctoral Fellowship (competitive), University of Cambridge 2011

NUI Travelling Studentship in the Sciences 2007

Cambridge European Trust Scholarship (Honorary) 2007

IRC Government of Ireland Postgraduate Scholarship (offer declined) 2007

DARPA Spins in Solids Summer Scholarship, University of Virginia 2006

SFI UREKA Individual summer research award 2005