*Ab initio* codes developed within the ETSF cover a wide field of application ranging from molecules and nano-scale clusters to 1D, 2D and 3D extended systems. The physical quantities provided by these programs include:

- ground-state electronic density and total energy from density functional theory (DFT);
- quasi-particle energy within the GW approximation and its extensions;
- linear and non-linear response functions.

Through these physical quantities, a large variety of physical properties can be addressed:

- structural and vibrational properties;
- electronic properties;
- optical and dielectric properties;
- magnetic properties.

Clicking on the logos will bring you to the (external) websites of the codes.

ABINIT is a software suite to calculate the optical, mechanical, vibrational, and other observable properties of materials. Starting from the quantum equations of density-functional theory, one can build up to advanced applications with perturbation theories based on DFT, and many-body Green's functions (GW and DMFT).

ABINIT can calculate molecules, nanostructures and solids with any chemical composition. It comes with several complete and robust tables of atomic potentials.

On-line tutorials are available for the main features of the code, and several schools and workshops are organized each year.

Demon2k (deMon = density of Montréal) is a software package for density functional theory (DFT) calculations. It uses the linear combination of Gaussian-type orbital (LCGTO) approach for the self-consistent solution of the Kohn-Sham (KS) DFT equations. The calculation of the four-center electron repulsion integrals is avoided by introducing an auxiliary function basis for the variational fitting of the Coulomb potential. The code is available free for academic use.

Main purposes:

- General purpose DFT code for ground states with MD, relaxation, QM/MM etc...
- Adaptive numerical integration for exchange-correlation functionals
- Auxiliary density functional theory (ADFT) and TD-ADFT
- Vibrational Spectroscopy

The DP code is an ab initio linear response TDDFT code implemented on a plane-wave basis set and NC pseudopotentials. It works in the frequency domain calculating in real space the basic quantities (the Kohn-Sham polarizability and the exchange-correlation kernel) and solving the fundamental TDDFT equations in reciprocal space. The approximations range from the most used RPA and TDLDA, to non-local (and/or non-adiabatic) kernels. Bulk systems are particularly well suited, but the code can be applied also to surfaces, 1D (tubes, wires) and 0D (clusters, molecules) systems.

Main purposes:

- Calculate EELS (Electron Energy-Loss Spectroscopy)
- IXSS (Inelastic X-ray Scattering Spectroscopy) at large transferred momentum Q
- Optical properties

EXC is an *ab initio* Bethe-Salpeter Equation code working in reciprocal space, in the frequency domain, and using a plane-wave basis set. Its purpose is to calculate dielectric and optical properties, like

- optical absorption, reflectivity, refraction index
- EELS (Electron Energy-Loss Spectroscopy)
- IXSS (Inelastic X-ray Scattering Spectroscopy)

It can be used on a large variety of systems, ranging from bulk systems, surfaces, to clusters or atoms (using the supercell method). Full coupling (beyond Tamm-Dancoff approximation) calculations are possible, as well as the possibility to speed up using the Haydock iterative scheme.

Octopus is a scientific program aimed at the ab initio virtual experimentation on a hopefully ever-increasing range of system types. Electrons are described quantum-mechanically within density-functional theory (DFT), in its time-dependent form (TDDFT) when doing simulations in time. Nuclei are described classically as point particles. Electron-nucleus interaction is described within the pseudopotential approximation. The code works for finite systems (including biomolecules in QM/MM), 3D periodic solids, and systems with mixed periodicity (i.e. polymers, slabs).

Main purposes:

- linear and nonlinear optical properties
- Raman, IR and other vibrational spectroscopies
- optical and magnetic dichroism
- non-adiabatic electron-ion dynamics
- optimal control theory

Yambo is also efficient and portable to the latest supercomputing architectures and benefits of a long-standing collaboration with parallel computing centers. The yambo suite thus provides all the ingredients for an advanced and computationally powerful approach to theoretical and computational material science.

__What can Yambo do?__

- Quasiparticle properties:
- GW self-energy in the Plasmon-Pole approximation;
- Full real-axis GW;
- Finite temperature electronic energies and lifetimes;
- Electron-phonon corrections;
- GW electron and phonon mediated self-energies;

- Spectroscopic Properties:
- Linear optical absorption:
- Electron Energy Loss;
- Kerr rotation;
- Temperature dependent spectroscopic properties;
- Real-Time dynamics: Time–dependent Screened Exchange;
- Nonlinear optical properties.

**exciting **is a full-potential all-electron density-functional-theory (DFT) package, implementing the linearized augmented plane-wave + local-orbital (LAPW+lo) method. It can be applied to all kinds of materials, irrespective of the atomic species involved, and also allows for the investigation of the atomic-core region. Features of ground-state calculations include atomic forces, structural optimization, elastic constants, phonons, and more. A particular focus lies on excited state properties, both within the framework of time-dependent DFT (TDDFT) as well as many-body perturbation theory (MBPT). The *GW* approach is implemented to work on top of a variety of (semi)local and hybrid functionals. The Bethe-Salpeter equation (BSE) is available for core and valence excitations. Most important spectroscopic probes:

- Linear and non-linear optical spectra
- Energy loss spectra
- X-ray spectra
- Raman spectraMagneto-optical Kerr effect (MOKE)

The code is freely available under the GNU General Public License (GPL).

## ELK

Elk is an all-electron full-potential linearised augmented-plane wave (FP-LAPW) code with many advanced features. The code is designed to be as simple as possible so that new developments in the field of density functional theory (DFT) can be added quickly and reliably. The code is freely available under the GNU General Public License.

Relevant activities:

- Optics
- Energy loss spectroscopy
- Photo-emission spectroscopy
- Vibrational spectroscopy
- X-rays spectroscopy

## Atomic Pseudopotential Engine

APE (Atomic Pseudopotential Engine) is a tool for generating atomic pseudopotentials within the Density-Functional Theory framework. The program can create pseudopotential files suitable for the most widely used ab-initio packages, and, besides the standard non-relativistic Hamann and Troullier–Martins potentials, it can generate pseudopotentials using the relativistic and semi-core extensions to the Troullier–Martins scheme.

Relevant activities:

- Optics
- Energy loss spectroscopy
- Quantum transport
- Time-resolved pectroscopy
- Photo-emission spectroscopy
- Vibrational spectroscopy
- X-rays spectroscopy