
March 28 2024 : Miguel’s work on the emergence of the hexagonal lattice in 2D Wigner fragments has just been publised in J. Phys. Chem. Lett.: J. Phys. Chem. Lett. (2024)

November 20 2023 : Gabriele’s work on the multichannel Dyson equation has just been published in Phys. Rev. Lett.: Phys. Rev. Lett. 131, 216401 (2023)

October 24 2023 : Gabriele has just successfully defended his Ph.D. thesis. Congratulations!

October 5 2023 : Amer’s work on the solution of the Thomson problem on a Clifford torus has just been published in J. Chem. Theory Comput.: J. Chem. Theory Comput. 19, 7423 (2023)

February 3 2023 : The 2023 edition of the LTTC winter school has just finished. The main focus of the school is to teach Master and Ph.D. students how to translate quantum theory into computer code.

January 6 2023 : Join our SEKT: Phys. Rev. B 107, 035111 (2023)

December 13 2022 : Miguel has just successfully defended his Ph.D. thesis. Congratulations!

November 3 2022 : Xabier’s work on the Wigner localization of electrons in an harmonic potential has just been published in the Journal of Chemical Physics: J. Chem. Phys. 157, 174107 (2022)

March 15 2022 : Gabriele’s work on the description of photemission spectra from the threebody Green’s function has just been published in the SciPost Physics: SciPost Phys. 12, 093 (2022)

February 14 2022 : Xabier Telleria Allika from the university of San Sebastian is visiting our group for three months to collaborate with us on the description of Wigner molecules.
Group
Gabriele Riva (Ph.D. student)
Amer Alrakik (Ph.D. student)
Stefano Paggi (Ph.D. student)
Daniele Lagasco (Ph.D. student)
Research
The aim of the TRIXS project is to develop the theory and software for the ab initio predictive description, without adjustable parameters, of Resonant Inelastic Xray Spectroscopy (RIXS).
Clifford boundary conditions
The goal of the Clifford project is to efficiently calculate properties of periodic manybody systems using Clifford boundary conditions and a renormalized distance in the Coulomb potential. Below is a short video I made for the APS March meeting explaining our approach.
Teaching
Bachelor
 Fundamentals of Chemistry
 Solid state chemisty
 Chemical Bonding
Master
 Statistical Thermodynamics
 Densityfunctional theory
 Quantum Dynamics
Ph.D.
 Manybody perturbation theory
 Densityfunctional theory
Publications
Latest publications
The Emergence of the Hexagonal Lattice in TwoDimensional Wigner Fragments Miguel Escobar Azor, Amer Alrakik, Louan de Bentzmann, Xabier TelleriaAllika, Alfredo S'anchez de Mer'as, Stefano Evangelisti, and J. Arjan Berger, J. Phys. Chem. Lett. 15, 3571 (2024)
Multichannel Dyson Equation: Coupling ManyBody Green’s Functions Gabriele Riva, Pina Romaniello and J. Arjan Berger, Phys. Rev. Lett. 131, 216401 (2023)
Solution to the Thomson Problem for Clifford Tori with an Application to Wigner Crystals Amer Alrakik, Miguel Escobar Azor, Véronique Brumnas, Gian Luigi Bendazzoli, Stefano Evangelisti, and J. Arjan Berger, J. Chem. Theory Comput. 19, 7423 (2023)
Mapping of Hückel zigzag carbon nanotubes onto independent polyene chains: Application to periodic nanotubes Grégoire François, Celestino Angeli, Véronique Brumnas, Gian Luigi Bendazzoli, Stefano Evangelisti, and J. Arjan Berger, J. Chem. Phys. 159 094106 (2023)
Screened extended Koopmans’ theorem: Photoemission at weak and strong correlation Stefano Di Sabatino, Jaakko Koskelo, J. Arjan Berger, and Pina Romaniello, Phys. Rev. B 107 035111 (2023)
The Wigner localization of interacting electrons in a onedimensional harmonic potential Xavier TelleriaAllika, Miguel Escobar Azor, Grégoire François, Gian Luigi Bendazzoli, Jon M. Matxain, X. Lopez, Stefano Evangelisti and J. Arjan Berger, J. Chem. Phys. 157, 174107 (2022)
Introducing screening in onebody density matrix functionals: Impact on charged excitations of model systems via the extended Koopmans’ theorem Stefano Di Sabatino, Jaakko Koskelo, J. Arjan Berger, and Pina Romaniello, Phys. Rev. B 105 235123 (2022)
Unique onebody position operator for periodic systems Stefano Evangelisti, Faten AbuShoga, Celestino Angeli, Gian Luigi Bendazzoli and J. Arjan Berger, Phys. Rev. B 105, 235201 (2022)
Photoemission spectral functions from the threebody Green’s function Gabriele Riva, Timothée Audinet, Matthieu Vladaj, Pina Romaniello and J. Arjan Berger, SciPost Phys. 12, 093 (2022)
Photoemission Spectra from the Extended Koopmans’ Theorem, Revisited, Stefano Di Sabatino, Jaakko Koskelo, Julien Prodhon, J. Arjan Berger, Michel Caffarel and Pina Romaniello, Frontiers in Chemistry 9, 746735 (2021)
Wigner localization in two and three dimensions: An ab initio approach Miguel Escobar Azor, Estefania Alves, Stefano Evangelisti and J. Arjan Berger, J. Chem. Phys. 155, 124114 (2021)
The localization spread and polarizability of rings and periodic chains Celestino Angeli, Gian Luigi Bendazzoli, Stefano Evangelisti and J. Arjan Berger, J. Chem. Phys. 155, 124114 (2021)
Accurate groundstate energies of Wigner crystals from a simple realspace approach, Estefania Alves, Gian Luigi Bendazzoli, Stefano Evangelisti and J. Arjan Berger, Phys. Rev. B 103, 245125 (2021)
Photoemission spectrum in paramagnetic FeO under pressure: Towards an ab initio description, Stefano Di Sabatino, Jaakko Koskelo, J. Arjan Berger, and Pina Romaniello, Phys. Rev. Research 3, 013172 (2021)
Clifford boundary conditions for periodic systems: the Madelung constant of cubic crystals in 1, 2 and 3 dimensions Nicolas Tavernier, Gian Luigi Bendazzoli, Véronique Brumas, Stefano Evangelisti, and J. Arjan Berger, Theo. Chem. Accounts 140, 106 (2021)
A Diagonalizationfree Optimization Algorithm for Solving KohnSham Equations of ClosedShell Molecules, Martin Mrovec and J. Arjan Berger, J. Comput. Chem., 42, 492 (2021)
Potential Energy Surfaces without Unphysical Discontinuities: The Coulomb Hole Plus Screened Exchange Approach, J. Arjan Berger , PierreFrançois Loos, and Pina Romaniello, J. Chem. Theory Comput. 17, 191 (2021)
Clifford boundary conditions: a simple directsum evaluation of Madelung constants Nicolas Tavernier, Gian Luigi Bendazzoli, Véronique Brumas, Stefano Evangelisti, and J. Arjan Berger, J. Phys. Chem. Lett. 11, 7090 (2020)
Optical spectra of 2D monolayers from timedependent density functional theory, Stefano Di Sabatino, J. Arjan Berger, and Pina Romaniello, Faraday Discussions 224, 467 (2020)
Accurate optical spectra from pure timedependent densityfunctional theory, S. Cavo, J. A. Berger, and P. Romaniello, Phys. Rev. B 101, 115109 (2020)
Wigner localization at extremely low densities: a numerically exact ab initio study, M. Escobar Azor, L. Brooke,, S. Evangelisti, T. Leininger, P.F. Loos, N. Suaud, and J. A. Berger, SciPost Phys. Core 1, 001 (2019)
ManyBody Effective Energy Theory: photoemission at strong correlation, Stefano di Sabatino, J. Arjan Berger, and Pina Romaniello, J. Chem. Theory Comput. 15, 5080 (2019)
A simple position operator for periodic systems, E. Aragao Valença, D. Moreno, S. Battaglia, G. L. Bendazzoli, S. Evangelisti, T. Leininger, N. Suaud, and J. A. Berger, Phys. Rev. B 99 205144 (2019)
Unphysical Discontinuities in GW Methods, Mickaël Véril, Pina Romaniello, J. Arjan Berger, and PierreFrançois Loos, J. Chem. Theory Comput. 14, 5220 (2018)
Distributed gaussian orbitals for the description of electrons in an external potential, L. Brooke, A. DiazMarquez, S. Evangelisti, T. Leininger, P.F. Loos, N. Suaud, and J. A. Berger, J. Mol. Mod. 24, 216 (2018)
Green Functions and SelfConsistency: Insights From the Spherium Model, PierreFrançois Loos, Pina Romaniello, and J. Arjan Berger J. Chem. Theory Comput. 14, 3071 (2018)
Optical properties from timedependent currentdensityfunctional theory: the case of the alkali metals Na, K, Rb, and Cs, Rubén Ferradás, J. Arjan Berger, and Pina Romaniello, Eur. J. Phys. B 91, 119 (2018)
Signatures of Wigner localization in onedimensional systems, A. DiazMarquez, S. Battaglia, G. L. Bendazzoli, S. Evangelisti, T. Leininger, and J. A. Berger, J. Chem. Phys. 148, 124103 (2018)
Revisiting the origin of satellites in core level photoemission of transparent conducting oxides: the case of ndoped SnO2, Francesco Borgatti, J. Arjan Berger et al., Phys. Rev. B 97, 155102 (2018)
Manybody perturbation theory and nonperturbative approaches: the screened interaction as key ingredient, Walter Tarantino, Bernardo S. Mendoza, Pina Romaniello, J. Arjan Berger, and Lucia Reining, J. Phys.: Cond. Matter. 30, 135602 (2018)
Selfconsistent Dyson equation and selfenergy functionals: An analysis and illustration on the example of the Hubbard atom, Walter Tarantino, Pina Romaniello, J. Arjan Berger, and Lucia Reining, Phys. Rev. B 96, 045124 (2017)
Optical properties of periodic systems within the currentcurrent response framework: Pitfalls and remedies, Davide Sangalli, J. Arjan Berger, Claudio Attaccalite, Myrta Grüning, and Pina Romaniello Phys. Rev. B 95, 155203 (2017)
Photoemission spectra from reduced density matrices: the band gap in strongly correlated systems, Stefano Di Sabatino, J. Arjan Berger, Lucia Reining, and Pina Romaniello Phys. Rev. B 94, 155141 (2016)
Gaugeinvariant Formulation of Circular Dichroism Nathaniel Raimbault, Paul L. de Boeij, Pina Romaniello, and J. Arjan Berger, J. Chem. Theory Comput. 12, 3278 (2016)
Fully parameterfree calculation of optical spectra for insulators, semiconductors and metals from a simple polarization functional J. Arjan Berger, Phys. Rev. Lett. 115, 137402 (2015)
Unphysical and Physical Solutions in ManyBody Theories: from Weak to Strong Correlation, Adrian Stan, Pina Romaniello, Santiago Rigamonti, Lucia Reining, and J. Arjan Berger, New J. Phys. 17, 093045 (2015)
GaugeInvariant Calculation of Static and Dynamical Magnetic Properties from the Current Density, Nathaniel Raimbault, Paul L. de Boeij, Pina Romaniello, and J. Arjan Berger, Phys. Rev. Lett. 114, 066404 (2015)
Reduced DensityMatrix Functional Theory: correlation and spectroscopy, Stefano Di Sabatino, J. Arjan Berger, Lucia Reining, and Pina Romaniello, J. Chem. Phys. 143, 024108 (2015)