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 6.1.

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.
• 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.

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.
• QHA: utilities for the calculation of projected density of states (PDOS) and of the free energy in the Quasi-Harmonic Approximation (to be used in conjunction with PHonon).
• PlotPhon: phonon dispersion plotting utility (to be used in conjunction with PHonon).

A copy of required external libraries is also included. Finally, several additional packages that exploit data produced by QUANTUM ESPRESSO or patch some QUANTUM ESPRESSO routines can be installed as plug-ins:

• 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.
• PLUMED: calculation of free-energy surface through metadynamics.
• GIPAW (Gauge-Independent Projector Augmented Waves): NMR chemical shifts and EPR g-tensor.
• GWL: electronic excitations within GW Approximation.
• WEST: Many-body perturbation corrections for standard DFT.

Documentation on single packages can be found in the Doc/ or 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) and GPU-accelerated machines. QUANTUM ESPRESSO also runs on Mac OS X and MS-Windows machines: see section 2.2.

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

• the Doc/ directory of the QUANTUM ESPRESSO distribution;
• the QUANTUM ESPRESSO 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 Developer Manual: Doc/developer_man.pdf.

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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