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Schools

Advanced computing of excited state properties in solids and nanostructures with Yambo

April 24, 2017 to April 28, 2017
Location : CECAM-HQ-EPFL, Lausanne, Switzerland
   EPFL on iPhone

Organisers

  • Myrta Gruning (Queen's University Belfast, United Kingdom)
  • Conor Hogan (CNR-ISM, Rome and University of Rome Tor Vergata, Italy)
  • Andrea Marini (National Research Council, Italy)
  • Alejandro Molina-Sánchez (University of Luxembourg, Luxembourg)
  • Daniele Varsano (S3, CNR Istituto di Nanoscienze, Italy)

Supports

   EU MaX CoE

   CECAM

   Psi-k

University of Luxembourg

Description

Important information for application:

Application deadline: 24 February 2017.
Applicants should have a working knowledge of a DFT or quantum-chemistry code.

The number of participants will be limited to approx. 30.
The organization will partially cover living expenses (hotel) of the participants.

Acceptance decisions will be made within 1 week after the deadline on the basis of motivations and CV provided at the moment of application.

School description:

Characterization and engineering of advanced materials and nanostructures often require an accurate description of their excited state properties. This school will provide a balanced training both in the fundamental theory of electronic and optical excitations as well as practical strategies for computation of such challenging systems within a massively parallel environment. In particular, lecturers and invited experts will:

(1) discuss the formalism of the description of electronic excitations (fundamentals of many body Green’s function theory, as well as technical aspects);

(2) contextualise the practical strategies and motivations on a larger scale; and

(3) demonstrate practical applications using the Yambo code.

Our goal is to equip students with the fundamental knowledge, practical skills and computational tools needed to tackle today’s challenging problems in materials science.

Four main topics will be covered through a synergetic mixture of invited keynote talks (K), theoretical or conceptual lectures (L), technical lectures and demonstrations (T), and dedicated hands-on sessions (H):

1. Computer simulations of large and challenging systems:
(a) State of the art approaches in computational material science: high throughput
methods, materials engineering and automated benchmarking (K - Nicola Marzari)
(b) Trends in high performance computing and programming paradigms (K - Carlo Cavazzoni)
(c) Overview of the Yambo code: installation, compilation, and basic usage (T, H)
(d) The Yambo project in a massively parallel environment: avoiding I/O, memory distribution, and hybrid MPI/openMP parallelization (T, H);
(e) Development of Yambo for personal or community use (H)
(f) Automated control and convergence testing with Yambo-python (H)

2. Fundamentals and strategies for computing electronic excitations:
(a) Approaches beyond standard Density Functional Theory (DFT): successes and limitations (L)
(b) Green’s function techniques and concepts: diagrammatic approach to many body
perturbation theory (L)
(c) Quasiparticles, self energy, Hedin’s equations, self consistency (L)
(d) Linear response theory (L)

3. One particle (charged) excitations:
(a) The GW approach: photoemission spectroscopy, spectral functions, convergence testing and practical use on massively parallel architectures (L, H)
(b) Advanced topics in GW with Yambo: real axis integration and quasiparticle lifetime calculations (L, H)
(c) GW implementations in other codes: localized basis strategies (K - Xavier Blase)

4. Two particle (neutral) excitations:
(a) Excitations in molecules (vertical excitations and dynamical polarizabilities) and in extended systems (optical absorption and electron energy loss spectra) (L)
(b) The Bethe Salpeter (BSE) and time dependent DFT (TD-DFT) approaches: a comparison (L)
(c) Numerical issues: inversion vs diagonalization vs iterative methods, Tamm Dancoff approximation, scalability (T)
(d) Practical analysis and post-processing of a paradigmatic 2D system: exciton analysis, band structure fitting, and Coulomb cutoff in bulk and single layer hexagonal BN, and other layered materials (H)

The three keynote talks (K) will be given by invited expert speakers from outside the Yambo community, and will cover advanced computational material science methods, trends in high performance computing, and alternative GW-BSE computational frameworks, respectively.
The main theory and technical lectures (L,T) will be given by experienced developers or users of the Yambo code (including some contributions from the school organisers).
The hands-on sessions (H) will be introduced by one of the developers and supervised by the organisers and Yambo developers.