## Software

# ABINIT

ABINIT is a suite of programs for materials science, which implements density functional theory, using a plane wave basis set and pseudopotentials, to compute the electronic density and derived properties of materials ranging from molecules to surfaces to solids. It implements density functional theory by solving the Kohn–Sham equations describing the electrons in a material, expanded in a plane wave basis set and using a self-consistent conjugate gradient method to determine the energy minimum. Computational efficiency is achieved through the use of fast Fourier transforms, and pseudopotentials to describe core electrons. As an alternative to standard norm-conserving pseudopotentials, the projector augmented-wave method may be used. In addition to total energy, forces and stresses are also calculated so that geometry optimizations and ab initio molecular dynamics may be carried out. Materials that can be treated by ABINIT include insulators, metals, and magnetically ordered systems including Mott-Hubbard insulators.

# Atomic Simulation Environment (ASE)

The Atomic Simulation Environment (ASE) is a set of tools and Python modules for setting up, manipulating, running, visualizing and analyzing atomistic simulations.

# CRYSTAL

Computational tool for solid state physics and chemistry. The CRYSTAL package performs ab initio calculations of the ground state energy, energy gradient, electronic wave function and properties of periodic systems. Hartree-Fock or Kohn- Sham Hamiltonians (adopting an Exchange-Correlation potential following the DFT postulates of ) can be used. Systems periodic in 0 (molecules, 0D), 1 (polymers, 1D), 2 (slabs, 2D), and 3 dimensions (crystals, 3D) are treated on an equal footing. In each case the fundamental approximation made is the expansion of the single particle wave functions ('Crystalline Orbital', CO) as a linear combination of Bloch functions (BF) defined in terms of local functions, i.e. Atomic Orbitals.

# FDMNES

The aim of the FDMNES project is to supply to the community a user friendly code to simulate x-ray spectroscopies, linked to the real absorption (XANES, XMCD) or resonant scattering (RXD) of the synchrotron radiation. This ab initio approach, wants to eliminate all the methodological parameters. First mainly mono-electronic, using the functionnal density theory (DFT), it includes now multi-electronics advances with the use of the time dependant DFT (TD-DFT) for a better taking into account of the excited states linked to the photon-matter interaction. It includes also the Hubbard correction (LDA+U) for a better description of the so called correlated materials.

# Materials Studio

Materials Studio is a modeling and simulation environment designed to allow to predict and understand the relationships of a material’s atomic and molecular structure with its properties and behavior. With it one can construct, manipulate and view models of molecules, crystalline materials, surfaces, polymers, and mesoscale structures. Materials Studio includes quantum, atomistic (or “classical”), mesoscale, and statistical methods that enable one to evaluate materials at various particle sizes and time scales. It also includes tools for evaluating crystal structure and crystal growth.

# OCEAN

OCEAN is a versatile package for performing first-principles calculations of core edge spectroscopy. The many-body method is based on ground-state density-functional theory (DFT) and uses the Bethe-Salpeter equation. OCEAN utilizes the programs ABINIT or QuantumESPRESSO for ground-state DFT portion of the calculations. OCEAN is capable of producing various spectra including X-ray absorption near-edge spectra (XANES), X-ray emission spectra (XES), and non-resonant inelastic X-ray scatter (NRIXS or XRS). OCEAN is the result of collaboration between the Rehr group at the University of Washington and Eric Shirley at the National Institute of Standards and Technology (USA).

# Quantum Espresso

Quantum ESPRESSO (QE) is an integrated suite of Open-Source computer codes for ab initio quantum chemistry methods of electronic-structure calculations and materials modeling at the nanoscale. It is based on density functional theory, density functional perturbation theory, plane wave basisi sets, and pseudopotentials. The core plane wave DFT functions of QE are provided by the PWscf (Plane-Wave Self-Consistent Field) component,

# VASP

VASP is an ab initio simulation package based on DFT. It is used for atomic scale materials modelling, e.g. electronic structure calculations and quantum-mechanical molecular dynamics from first principles. VASP computes an approximate solution to the many-body Schrödinger equation, either within density functional theory (DFT), solving the Kohn-Sham equations, or within the Hartree-Fock (HF) approximation, solving the Roothaan equations. Hybrid functionals that mix the Hartree-Fock approach with DFT are implemented as well. Furthermore, Green's functions methods (GW quasiparticles, and ACFDT-RPA) and many-body perturbation theory (2nd-order Møller-Plesset) are available. Central quantities, like the one-electron orbitals, the electronic charge density, and the local potential are expressed in plane wave basis sets. The interactions between the electrons and ions are described using norm-conserving or ultrasoft pseudopotentials, or the projector-augmented-wave method. To determine the electronic ground state, VASP makes use of efficient iterative matrix diagonalisation techniques, like the residual minimisation method with direct inversion of the iterative subspace (RMM-DIIS) or blocked Davidson algorithms. These are coupled to highly efficient Broyden and Pulay density mixing schemes to speed up the self-consistency cycle.

# WIEN2k

The program package WIEN2k allows to perform electronic structure calculations of solids using density functional theory (DFT). It is based on the full-potential (linearized) augmented plane-wave ((L)APW) + local orbitals (lo) method, one among the most accurate schemes for band structure calculations. WIEN2k is an all-electron scheme including relativistic effects.

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