Stefano Baroni

E-mail

 baroni (at) sissa.it

Office

 A 408

Web

 http://stefano.baroni.me

Tel

 +39 040 3787 406

Fax

 +39 040 3787 528

Vita

Stefano Baroni, born 1955, was nominated associate professor of theoretical condensed-matter physics at SISSA in 1988, after spending five years as a postdoc at the Ecole Polytechnique Fédérale de Lausanne, and four years at the University of Trieste as an assistant professor (ricercatore). In 1999 he became full professor at SISSA where, from 2008, he coordinates the condensed-matter theory and simulation group (sector). From 1994 to 1998 he was the director of the Centre Européen de Calcul Atomique et Moléculaire at the Ecole Normale Supérieure de Lyon. In 2002 SB founded the DEMOCRITOS National Simulation Center of the Italian National Institute for the Physics of Matter (INFM), now part of the National Research Council (CNR), which he directed until 2008. SB has held visiting professorships and scholarships in many scientific institutions worldwide, including the Ecole Polytechnique Fédérale de Lausanne, the University of Calfornia at Santa Barbara, the Princeton University, the University of Minnesota, University College London (as a Leverhulme professor), the University of Sidney, and the Fudan University in Shanghai. SB is the coordinator of the Quantum ESPRESSO project for the design, implementation, maintenance, and distribution of high-quality high-performance software for the quantum simulation of materials, mainly based on density-functional theory.

Research

The leitmotif of SB’s research over the years has been the development of new theoretical ideas and numerical tools allowing for the computation of properties and simulation of processes otherwise inaccessible to a quantitative theoretical investigation. SB’s research has touched on several and diverse applications, including semiconductor interfaces and alloys, the chemical reactivity of metal surfaces and catalysis, lattice dynamics and related materials properties, including those occurring at extreme pressure and temperature conditions, and the dynamical properties of quantum systems, such as e.g. small helium clusters. He is known for pioneering different quantum simulation methods, among which the most widely know are probably density-functional perturbation theory, used for simulating lattice and molecular vibrations, and reptation quantum Monte Carlo, a path-integral technique used for simulating static and dynamical properties of interacting quantum systems. In the next few years this  research will be further pursued along the following lines:

  1. Optical properties of complex molecular and nano-structured systems. Conventional quantum simulation methods based on density-functional theory (DFT) are unable to address dynamical processes involving charge excitations. More accurate techniques based on time-dependent density-functional theory (TDDFT) or many-body perturbation theory (MBPT), though potentially apt to treat these phenomena, have been limited so far to model systems of rather limited size (one to two order of magnitudes smaller than those currently treated using DFT). Building on our a novel Lanczos approach to TDDFT and to MBPT, we will address the optical excitation spectra of systems in the hundreds-of-atoms size range, with applications to biological molecules and photovoltaic devices. This research line will be carried on in collaboration with Ralph Gebauer (ICTP) Paolo Umari (CNR and University of Padua).
  2. Slow dynamics in classical and quantum systems. Some 10 years ago SB, in collaboration with Ralph Gebauer, then a PhD student of his, provided an unified approach to the low-energy dynamics of many quantum systems, based on the adiabatic decoupling of a suitable (collection of) collective variable(s). In collaboration with Ralph Gebauer (now staff at the ICTP) this approach is being further generalized and will be applied to different quantum phenomena including collective tunneling in many-body systems and electronic transport in molecular devices. A different approach to the same problem will be pursued in collaboration with Alessandro Laio: the isomorphism between the Fokker-Planck equation for the overdumped Langevin dynamics and the Schrödinger equation in imaginary time will be used, in conjuction with path-integral techniques borrowed from reptation quantum Monte Carlo, to compute tunneling splitting in quantum systems from transition rates in suitably defined classical models.
  3. Software engineering. SB is the main promoter of the Quantum ESPRESSO (QE) project. This project will be pursued along four main lines: 1) enhancing the capabilities, by addressing more properties, particularly as concerns excited states; 2) enhancing the performances, particularly as concerns massively parallel architectures enabling peta- and exa-scale computing; 3) enhancing user friendliness through scriptable and graphical user interfaces; 4) enhancing the validation and reproducibility of the codes, by making QE interoperable with other software and by publishing libraries of pseudopotentials and of benchmarks.

Publications

SB is the author of more than 200 scientific papers published in international journals and refereed conference proceedings (174 on ISI: 3 renowned, 500+ quotes; 1 famous, 250-499 quotes; 13 very well know, 100-249 quotes). These papers have been cited more than 7,800 times in the international literature (H41, source: ISI, January 2011).

Among SB’s papers, the most significant include:

  1. P. Giannozzi, S. Baroni et al., Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials, J. Phys. Condensed Matter 21, 395502 (2009).
  2. B. Walker, A.M. Saitta, R. Gebauer, and S. Baroni, Efficient approach to time-dependent density-functional perturbation theory for optical spectroscopy, Phys. Rev. Lett. 96, 113001 (2006).
  3. A. Kokalj, N. Bonini, S. de Gironcoli, C. Sbraccia, G. Fratesi, and S. Baroni, Methane Dehydrogenation on Rh@Cu(111): A First-Principles Study of a Model Catalyst, J. Am. Chem. Soc. 128, 12448 (2006).
  4. S. Moroni, A. Sarsa, S. Fantoni, K.E. Schmidt, and S. Baroni, Structure, rotational dynamics, and superfluidity  of small OCS-doped He clusters, Phys. Rev. Lett.  90, 143401 (2003).
  5. S. Baroni, S. de Gironcoli, A. Dal Corso, and P. Giannozzi, Phonons and related properties of extended systems from density-functional perturbation theory, Rev. Mod. Phys. 73, 515 (2001).
  6. S. Baroni and S. Moroni, Reptation quantum Monte Carlo: a method for unbiased ground-state averages and imaginary-time correlations, Phys. Rev. Lett. 82, 4745 (1999).
  7. A. Debernardi, S. Baroni, and E. Molinari, Anharmonic phonon lifetimes in semiconductors from density-functional perturbation theory, Phys. Rev. Lett. 75, 1819 (1995).
  8. S. Baroni and P. Giannozzi, Towards very large-scale electronic-structure calculations, Europhys. Lett. 17, 547 (1992).
  9. A. Baldereschi, S. Baroni, and R. Resta, Band offsets in lattice-matched heterojunctions: a model and first-principles calculations for GaAs/AlAs, Phys. Rev. Lett. 61, 734 (1988).
  10. S. Baroni, P. Giannozzi, and A. Testa, Green’s Function approach to linear response in solids, Phys. Rev. Lett. 58 1861 (1987).

A complete list of SB’s scientific papers can be found here.