Abstract

Density-functional theory (DFT) is a standard tool to investigate the properties of electronic systems. In spite of its success due to the advantageous polynomial scaling with the size of the system, DFT is a ground-state theory and though it is routinely applied to calculate excited state properties, its accuracy is inevitably limited. The past two decades have seen the developments of approaches based on many-body perturbation theory used in combination with DFT to predict excited states properties of materials. Rather than the ground-state density – which in principles gives access to any ground-state property of an electron system – the key quantities of these approaches are the one-particles and two-particles Green’s functions which are closely related to the relevant excited state processes. In this lecture, I will introduce some key ideas behind these approaches and show how they are used in practice for predicting materials’ properties. To conclude, I will offer a perspectives on some current developments in the field.