yambo: An ab initio tool for excited state calculations

A detailed description on how electronic systems interact with electro-magnetic radiation is the starting point for understanding numerous phenomena in Physics, Chemistry, Biology and for developing new technologies (e.g. photovoltaics cells). Ab-initio numerical simulations are increasingly used to support, interpret and guide experimental works. In particular, approaches based on Many-Body perturbation theory such as the GW approximation and the Bethe–Salpeter equation are becoming a standard tool in the calculations of quasiparticle energies (related to direct and inverse photoelectron measurements) and the macroscopic dielectric function (related to e.g optical absorption or electron-energy loss experiments). yambo [1] is an ab initio code for
calculating quasiparticle energies and optical properties of electronic systems within the framework of many-body perturbation theory and time-dependent density functional theory. Quasiparticle energies are
calculated within the GW approximation for the self-energy. Optical properties are evaluated either by solving the Bethe–Salpeter equation or by using the adiabatic local density approximation. yambo is a plane-wave code that, although particularly suited for calculations of periodic bulk systems, has been applied to a large variety of physical systems. yambo relies on efficient numerical techniques devised to treat systems with reduced dimensionality, or with a large number of degrees of freedom. The code has a user-friendly command-line based interface, flexible I/O procedures and is interfaced to several publicly available density functional ground-state codes.

After a quick review of the theoretical approaches I will present the basic features of Yambo as well as some more advanced ones and showcase typical applications. Finally I will give an overview of recent or in-progress developments (e.g. yambo for HPC, real-time implementation, etc...)

[1] A. Marini, C. Hogan, M.G. and D. Varsano Comp. Phys. Comm. 180, 1392 (2009)