Beyond DFT Team @ THEOS
Members
Nicola Marzari (EPFL)
Tommaso Chiarotti (EPFL)
Mario Caserta (EPFL)
Alumni:
Nicola Colonna (currently @ PSI)
Matteo Cococcioni (currently @ University of Pavia)
Iurii Timrov (currently @ PSI)
Edward Baxter Linscott (currently @ PSI)
Marco Vanzini
Francesco Aquilante
Riccardo De Gennaro
Research:
- Hubbard-corrected functionals (DFT+U and DFT+U+V): Predictive modeling of transition-metal and rare-earth compounds and of their physical properties is crucial for the development of many technologies including, for example, biomimetic photochemistry, catalysis, solar cells, accumulation devices as Li-, Na-, Mg-ion or Li-air batteries, recovery of waste heat through ferroelectricity, superconductivity, sensing and actuation, spintronics, multiferroics, quantum information. Unfortunately, first-principles calculations based on density-functional theory (DFT), almost an obligated choice to approach the study of systems of realistic complexity, suffer from the inability of most approximate energy functionals to capture ground states characterized by strongly localized and possibly correlated electrons. One of the corrective schemes that are used to alleviate these difficulties is based on the addition of Hubbard functionals acting on localized (atomic-like d or f) states, according to the so-called DFT+U scheme [1]. The most advanced approach, named DFT+U+V, is actually based on the extended Hubbard model with on-site and inter-site electronic interactions and allows to capture electronic localization even in presence of significant hybridization [2]. This extended corrective scheme is used in the study of a number of transition-metal compounds including materials for Li-ion batteries and complex oxides investigated for photo-catalysis. The group also develops and maintains a computational tool, based on density-functional perturbation theory (DFPT) [3], to compute the effective interaction parameters (U and V) from first-principles. The method of Ref. [3] has been implemented in the open-source Quantum ESPRESSO distribution and it is publicly available.
- Koopmans-compliant spectral functionals: The interpretation of experimental spectra, such as those obtained with ultraviolet photoemission spectroscopy (UPS) or angular-resolved photoemission spectroscopy (ARPES), often requires theoretical support, due to the complexity of the data involved. From a theoretical point of view, photoemission spectra can be studied with many-body perturbation theory, density-matrix functional theory or with the wave function methods of quantum chemistry. However, due to the significant computational requirements of these approaches, and their own limits in terms of ultimate accuracy, applications are limited in system size and complexity. For these reasons simpler methods such as Hartree-Fock or ground-state DFT are still frequently employed to interpret photoemission spectra. However DFT is a ground state theory and there is obvious connection between the single particle energies of the auxiliary Kohn-Sham systems and the charged excitation of the real interacting systems. On the other side, Hatree-Fock eigenvalues do have a meaning of additional/removal energies, but miss important relaxation effects. Dabo and collaborators have introduced Koopmans-compliant (KC) functionals [4-6] to enforce a generalized criterion of piecewise linearity with respect to the fractional removal or addition of an electron from any orbital (and not only the HOMO) in approximate DFT functionals, and to extend to the entire electronic manifold the self-interaction linearization imposed by DFT + Hubbard U [1]. The condition of Koopmans' compliance is naturally akin to that of enforcing a correct description of charged excitations, and thus can lead to orbital energies that are comparable to the quasiparticle excitations of photoemission experiments [7-9]. Notably all this is achieved using just a functional formulation for spectral properties and thus bypassing completely more expensive and cumbersome diagrammatic techniques.
News
- 21/02/2023: Check out our new article [23] that describes the electronic properties and intercalation voltages of spinel Li-ion cathode materials from extended Hubbard functionals.
- 31/10/2022: Check out our new article [22] that describes the electronic properties and intercalation voltages of olivine-type Li-ion cathode materials from extended Hubbard functionals.
- 15/08/2022: Check out our new article [21] that describes the structural, electronic, and magnetic properties of the pristine and Fe-doped alpha-MnO2 using DFT with extended Hubbard functionals.
- 07/07/2022: Check out our new article [20] that describes the open-source HP code (which is part of Quantum ESPRESSO) for computing Hubbard parameters using density-functional perturbation theory.
- 06/07/2022: Fresh off the press: our latest article in Phys. Rev. B describes how to extract Koopmans band structures for the first time [19]
- 04/10/2021: Check out our new article [18] that highlights the importance of inter-site Hubbard interactions in the beta phase of MnO2 using DFT+U+V.
- 16/09/2021: Check out our new article [17] that presents a new method for the first-principles calculation of the electron-phonon interactions in correlated electron systems.
- 29/01/2021: Check out our new article [16] that describes how to compute Hubbard parameters self-consistently using density-functional perturbation theory in the ultrasoft and projector-augmented wave formulations.
- 28/12/2020: Check out our new article [15] that describes how to compute Hubbard forces exactly when using orthogonalized atomic orbitals as a Hubbard manifold.
- 19/08/2020: Our new article [14] outlines the crucial role of extended Hubbard functionals to describe the electronic structure of complex transition-metal oxides such as pristine and Ni-substituted LaFeO3, and paves the way to future studies on similar systems.
- 09/07/2020: Our new article [13] about the self-consistent DFT+U+V study of oxygen vacancies in SrTiO3.
- 19/02/2020: Our new article [12] on the Hubbard-corrected density functional perturbation theory with ultrasoft pseudopotentials was published today in Phys. Rev. B!
- 12/03/2019: In our latest article [11] we show how Koopmans functionals can predict the ionization potential of small molecules with an accuracy comparable to GW but at a fraction of the computational cost
- 08/03/2019: Check out our new article [10] on the application of the DFPT approach to calculate self-consistent site-dependent Hubbard U parameter in stoichiometric and defective SrMnO3. This work was done in collaboration within MARVEL with Dr. Chiara Ricca and Prof. Ulrich Aschauer (University of Bern).
- 16/08/2018: Our new article [3] on the ab initio calculation of the effective Hubbard U parameter using density-functional perturbation theory was published today in Phys. Rev. B!
- 23/05/2018: Our recent work on the extension of Koopmans' functional to periodic systems [7] appeared in Physical Review X!
Publications
- [1] Matteo Cococcioni and Stefano de Gironcoli, Linear response approach to the calculation of the effective interaction parameters in the LDA+U method, Phys. Rev. B 71, 035105 (2005)
- [2] Vivaldo Leiria Campo Jr and Matteo Cococcioni, Extended DFT+U+V method with on-site and inter-site electronic interactions, J. Phys.: Condens. Matter 22, 055602 (2010)
- [3] Iurii Timrov, Nicola Marzari, and Matteo Cococcioni, Hubbard parameters from density-functional perturbation theory, Phys. Rev. B 98, 085127 (2018) (arXiv:1805.01805)
- [4] Ismaila Dabo, Andrea Ferretti, Nicolas Poilvert, Yanli Li and Nicola Marzari, Koopmans' condition for density-functional theory, Phys. Rev. B 82 , 115121 (2010)
- [5] Giovanni Borghi, Andrea Ferretti, Ngoc Linh Nguyen, Ismaila Dabo and Nicola Marzari, Koopmans-compliant functionals and their performance against reference molecular data, Phys. Rev. B 90 , 075135 (2014)
- [6] Nicola Colonna, Ngoc Linh Nguyen, Andrea Ferretti and Nicola Marzari, Screening in Orbital-Density-Dependent Functionals, J. Chem. Theory Comput. 14 2549 (2018)
- [7] Ngoc Linh Nguyen, Nicola Colonna, Andrea Ferretti, and Nicola Marzari Koopmans-Compliant Spectral Functionals for Extended Systems, Phys. Rev. X 8, 021051 (2018)
- [8] Ngoc Linh Nguyen, Giovanni Borghi, Andrea Ferretti, Ismaila Dabo and Nicola Marzari, First-Principles Photoemission Spectroscopy and Orbital Tomography in Molecules from Koopmans-Compliant Functionals, Phys. Rev. Lett. 114, 166405 (2015)
- [9] Ngoc Linh Nguyen, Giovanni Borghi, Andrea Ferretti and Nicola Marzari First-Principles Photoemission Spectroscopy of DNA and RNA Nucleobases from Koopmans-Compliant Functionals, J. Chem. Theory Comput. 12, 3948 (2016)
- [10] Chiara Ricca, Iurii Timrov, Matteo Cococcioni, Nicola Marzari, and Ulrich Aschauer Self-consistent site-dependent DFT+U study of stoichiometric and defective SrMnO3, Phys. Rev. B 99, 094102 (2019); arXiv:1811.10858
- [11] Nicola Colonna, Ngoc Linh Nguyen, Andrea Ferretti and Nicola Marzari Koopmans-compliant functionals and potentials and their application to the GW100 test set, J. Chem. Theory Comput., 15 (2019)
- [12] A. Floris, I. Timrov, B. Himmetoglu, N. Marzari, S. de Gironcoli, and M. Cococcioni Hubbard-corrected density functional perturbation theory with ultrasoft pseudopotentials, Phys. Rev. B 101, 064305 (2020); arXiv:1910.06195
- [13] C. Ricca, I. Timrov, M. Cococcioni, N. Marzari, and U. Aschauer Self-consistent DFT+U+V study of oxygen vacancies in SrTiO3, Phys. Rev. Research 2, 023313 (2020); arXiv:2001.06540
- [14] I. Timrov, P. Agrawal, X. Zhang, S. Erat, R. Liu, A. Braun, M. Cococcioni, M. Calandra, N. Marzari, and D. Passerone Electronic structure of pristine and Ni-substituted LaFeO3 from near edge x-ray absorption fine structure experiments and first-principles simulations, Phys. Rev. Research 2, 033265 (2020); arXiv:2004.04142
- [15] I. Timrov, F. Aquilante, L. Binci, M. Cococcioni, and N. Marzari Pulay forces in density-functional theory with extended Hubbard functionals: From nonorthogonalized to orthogonalized manifolds, Phys. Rev. B 102, 235159 (2020); arXiv:2010.13485
- [16] Iurii Timrov, Nicola Marzari, and Matteo Cococcioni, Self-consistent Hubbard parameters from density-functional perturbation theory in the ultrasoft and projector-augmented wave formulations, Phys. Rev. B 103, 045141 (2021); arXiv:2011.03271
- [17] Jin-Jian Zhou, Jinsoo Park, Iurii Timrov, Andrea Floris, Matteo Cococcioni, Nicola Marzari, and Marco Bernardi, Ab Initio Electron-Phonon Interactions in Correlated Electron Systems, Phys. Rev. Lett. 127, 126404 (2021); arXiv:2102.06840
- [18] Ruchika Mahajan, Iurii Timrov, Nicola Marzari, Arti Kashyap, Importance of intersite Hubbard interactions in β-MnO2: A first-principles DFT+U+V study, Phys. Rev. Materials 5, 104402 (2021); arXiv:2106.00520
- [19] Riccardo De Gennaro, Nicola Colonna, Edward Linscott, Nicola Marzari, Bloch's theorem in orbital-density-dependent functionals: Band structures from Koopmans spectral functionals, Phys. Rev. B 106, 035106 (2022)
- [20] Iurii Timrov, Nicola Marzari, Matteo Cococcioni HP – A code for the calculation of Hubbard parameters using density-functional perturbation theory, Comput. Phys. Commun. 279, 108455 (2022); arXiv:2203.15684
- [21] Ruchika Mahajan, Arti Kashyap, and Iurii Timrov Pivotal Role of Intersite Hubbard Interactions in Fe-Doped α-MnO2, J. Phys. Chem. C 126, 14353 (2022); arXiv:2205.05977
- [22] Iurii Timrov, Francesco Aquilante, Matteo Cococcioni, and Nicola Marzari Accurate Electronic Properties and Intercalation Voltages of Olivine-Type Li-Ion Cathode Materials from Extended Hubbard Functionals, PRX Energy 1, 033003 (2022); arXiv:2203.15732
- [23] Iurii Timrov, Michele Kotiuga, and Nicola Marzari Unraveling the effects of inter-site Hubbard interactions in spinel Li-ion cathode materials, Phys. Chem. Chem. Phys. 25, 9061 (2023); arXiv:2301.11143