The European Theoretical Spectroscopy Facility (ETSF) is a recently created distributed network that offers theoretical calculations and open source software code to help interpret experimental data. It is a virtual facility that supplies services, support, and information to experimental and industrial users.

The ETSF employs a wide range of theoretical and computational methods to study electrons in nanostructures and materials and their interaction with external fields and light, the principal ones being:

Density Functional Theory (DFT):
• Kohn-Sham DFT for ground-state total energy calculations, structure determination, potential energy surfaces for atomic motion
• Time-dependent DFT for study of systems excited out of the ground state, e.g. optical absorption

Many Body Perturbation Theory (MBPT):
• GW and GWΓ self-energy approaches for electron addition and removal energies, spectral functions, total energy
• Bethe-Salpeter approach for neutral electronic excitations
• Non-equilibrium Green's function theories for Quantum Transport

Combined DFT-MBPT approaches:
• Generalised Kohn-Sham DFT for total energy calculations, incorporating elements of DFT and MBPT
• GWΓ self-energy, incorporating Density Functional concepts
• TDDFT approaches for quantum transport
• TDDFT approaches for total energy calculations, via the fluctuation-dissipation theorem

More information about the ETSF is available at www.etsf.eu