Workshop

# Questaal Hands-On Course

For those of you interested in getting some hands-on experience with the Questaal code, STFC Daresbury Laboratory in the UK will be hosting a tutorial course May 16-19, 2017. The full call is listed below. This workshop will be run by Mark van Schilfgaarde (main Questaal package developer), Leon Petit, Martin Lueders, and Myrta Gruening. A primary focus of the hands-on workshop will be on quasi-particle self-consistent *GW* (QSGW) theory and its applications.

STFC Daresbury Laboratory

3 1/2 days from the afternoon of the 16th through the 19th of May, 2017

To register please visit https://questaalworkshop.eventbrite.co.uk

This course will provide tutorials for both the theory of, and how to use, an all-electron code that implements both density functional theory and *GW*/quasi-particle self-consistent *GW* (QS*GW*) theory. The density-functional part is implemented with full potential generalization of the linearized muffin-tin orbitals (LMTO) theory, or LMTO+LAPW combined. We will also present a recent implementation of Dynamical Mean Field theory through an interface to Kristjan Haule’s implementation of Continuous time Quantum Monte Carlo (CTQMC). The interface can connect to CTQMC either with LDA or with QSGW; see this paper.

Questaal also includes a number of extensions, such as modules to calculate transport properties, magnetic properties, optical properties, etc. There is an implementation of the coherent potential approximation, making it possible to address systems with chemical or spin disorder within the LDA. Questaal also has a principal layer Green’s technique to transport though nonperiodic, layered systems. Some of these extensions will be presented in the tutorials.

The QS*GW* package contains an implementation in an all-electron context, *GW* theory based on the LDA, and also the quasi-particle self-consistent *GW* theory. The latter goes beyond standard *GW* theory as it does not use density functional theory as a reference, but a self-consistently determined non-interacting system which is by construction the optimal starting point for many body perturbation theory. QS*GW* is more reliable and universally applicable than standard density-functional based *GW*. Participants will have practical tutorials to gain experience in how to use the codes and analyse results. We will present several examples where QS*GW* predicts properties in cases where LDA based *GW* fares poorly, and discuss how DMFT, in a nonperturbative context, and ladder diagrams in many body perturbation theory, can help to surmount these limitations.

The course will last for 3 1/2 days. The mornings will consist of formal lectures wth theory by van Schilfgaarde and Gruening, followed by tutorials organised by developors or users of the code. The afternoon sessions are dedicated to practical exercises with the code. We plan the following schedule:

We cannot cover any transportation cost, but food and accommodation for the duration of the course will be provided free of charge.