# Welcome to the FHI-aims Tutorials Overview Page!

Please use this site to navigate through the available FHI-aims tutorials.

## Fundamentals of FHI-aims

This first section is all about fundamental aspects of running FHI-aims simulations for atoms, molecules, solids, and surfaces.

• Basics of Running FHI-aims

Learn about running FHI-aims for molecules (spin-unpolarized/-polarized) and solids. The syntax of the input files and the structure of the output files is explained. Find out how to request a structure optimization and to request the calculation of band structure and DOS for solids.

• Charge and Spin Initialization: Complex Materials Simulations

A tutorial that introduces FHI-aims for complex materials with non-trivial atomic and electronic structure. Key concepts include efficient initialization of ionic and spin-polarized solids and how to construct and simulate clusters, here demonstrated for the transition metal oxide Fe$$_2$$O$$_3$$.

• Slab calculations and surface simulations with FHI-aims

The basic techniques for surface simulations with FHI-aims are introduced. Learn how to construct, run a slab simulation, and extract and understand the relevant numbers from the output file.

• Scaling in FHI aims (Scaling of algorithms used in FHI-aims, strategies for big systems)

Learn about running FHI-aims on a supercomputer and the most important aspects that you should consider when running large-scale systems with many CPUs.

• Symmetry for Solids

A short tutorial about symmetry-use in solids.

• Free atoms - Calculating atomization energies

This section contains notes about how to control the self-consistent solution of free atoms, especially for open-shell atoms, where most density functionals may have more than one self-consistent solution. Finding the lowest-energy solution out of multiple possible ones for the electronic structure of free atoms in DFT is important in order to calculate atomization energies.

## Beyond DFT methods in FHI-aims

• RPA, GW, and BSE for Molecules and Solids

This tutorial focuses on many-body perturbation theory methods "beyond DFT" in FHI-aims. In particular, three main approaches are discussed:

1. The GW approximation for quasiparticle properties (i.e., charged excitations such as "electrons" and "holes" in semiconductors);
2. The random-phase approximation (RPA) to electron correlation energies, for total energies;
3. The Bethe-Salpeter equation (BSE) based on GW, for neutral (e.g., optical) excitation energies (in FHI-aims, currently available for non-periodic simulations of molecules).

## Motion of atoms

• Molecular Dynamics with i-PI

Introduction to running molecular dynamics (MD) through the software package i-PI. Following things are covered:

• How to use FHI-aims together with i-PI
• Microcanonical Ensemble and Importance of the step size
• Thermostats
• Vibrational analysis with i-PI
• Thermodynamic integration
• Simulations at constant pressure
• Phonons with FHI-vibes and more

• How to use FHI-aims through FHI-vibes
• Calculate Phonon properties: Band structure, DOS, Free Energy, ...
• Lattice expansion (uasi-harmonic approximation)
• Calculate Born-Effective Charges and non-analytical term correction for polar materials
• Band gap renormalization

## Data Management

• Managing research data - FHI-aims and AiiDA

This tutorial gives an overview on how to use the aiida-ase package to manage FHI-aims - driven calculations with AiiDA. AiiDA is an open-source "Automated interactive infrastructure and Database for computational science". It enables the creation of Python-based workflows, which can automatically be submitted to local and remote machines. AiiDA also keeps track of the origin and destination of files and conveniently stores all information in a database.

Other tutorials will appear at this page over time. We also note that further tutorials related to earlier versions of FHI-aims are available from past Hands-On workshop sites, e.g., the Hands-on DFT and Beyond workshop 2019.