1 Introduction

This guide gives a general overview of the contents and of the installation of QUANTUM ESPRESSO (opEn-Source Package for Research in Electronic Structure, Simulation, and Optimization), version 7.2.

Important notice: due to the lack of time and of manpower, this manual does not cover many important aspects and may contain outdated information.

The QUANTUM ESPRESSO distribution contains the core packages PWscf (Plane-Wave Self-Consistent Field) and CP (Car-Parrinello) for the calculation of electronic-structure properties within Density-Functional Theory (DFT), using a Plane-Wave (PW) basis set and pseudopotentials. It also includes other packages for more specialized calculations:

• PWneb: energy barriers and reaction pathways through the Nudged Elastic Band (NEB) method.
• PHonon: vibrational properties with Density-Functional Perturbation Theory (DFPT).
• PostProc: codes and utilities for data postprocessing.
• PWcond: ballistic conductance.
• XSPECTRA: K-, L₁-, L_{2, 3}-edge X-ray absorption spectra.
• TD-DFPT: spectra from Time-Dependent Density-Functional Perturbation Theory.
• GWL: electronic excitations within the GW approximation and with the Bethe-Salpeter Equation
• EPW: calculation of the electron-phonon coefficients, carrier transport, phonon-limited superconductivity and phonon-assisted optical processes;
• HP: calculation of Hubbard U parameters using DFPT;
• QEHeat: energy current in insulators for thermal transport calculations.
• KCW: quasiparticle energies of finite and extended systems using Koopmans-compliant functionals in a Wannier representation.

The following auxiliary packages are included as well:

• PWgui: a Graphical User Interface, producing input data files for PWscf and some PostProc codes.
• atomic: atomic calculations and pseudopotential generation.

A copy of required external libraries is either included or automatically downloaded from the net. Finally, several additional packages that exploit data produced by QUANTUM ESPRESSO or patch some QUANTUM ESPRESSO routines can be automatically installed using make:

• Wannier90: maximally localized Wannier functions.
• WanT: quantum transport properties with Wannier functions.
• YAMBO: electronic excitations within Many-Body Perturbation Theory, GW and Bethe-Salpeter equation.
• D3Q: anharmonic force constants.
• GIPAW (Gauge-Independent Projector Augmented Waves): NMR chemical shifts and EPR g-tensor.

For QUANTUM ESPRESSO with the self-consistent continuum solvation (SCCS) model, aka ``Environ'', see http://www.quantum-environment.org/.

Documentation on single packages can be found in the Doc/ directory of each package. A detailed description of input data is available for most packages in files INPUT_*.txt and INPUT_*.html.

The QUANTUM ESPRESSO codes work on many different types of Unix machines, including parallel machines using both OpenMP and MPI (Message Passing Interface). QUANTUM ESPRESSO also runs on Mac OS X and MS-Windows machines (see section 2.2). Since Feb.2021 the main repository also works with NVidia GPU's.

Further documentation, beyond what is provided in this guide, can be found in:

• the Doc/ and examples/ directories of the QUANTUM ESPRESSO distribution;
• the web site www.quantum-espresso.org;
• the archives of the mailing list: See section 1.2, ``Contacts'', for more info.

People who want to contribute to QUANTUM ESPRESSO should read the Wiki pages on GitLab: https://gitlab.com/QEF/q-e/-/wikis.

This guide does not explain the basic Unix concepts (shell, execution path, directories etc.) and utilities needed to run QUANTUM ESPRESSO; it does not explain either solid state physics and its computational methods. If you want to learn the latter, you should first read a good textbook, such as e.g. the book by Richard Martin: Electronic Structure: Basic Theory and Practical Methods, Cambridge University Press (2004); or: Density functional theory: a practical introduction, D. S. Sholl, J. A. Steckel (Wiley, 2009); or Electronic Structure Calculations for Solids and Molecules: Theory and Computational Methods, J. Kohanoff (Cambridge University Press, 2006). Then you should consult the documentation of the package you want to use for more specific references.

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