Welcome¶
Overview of the ABINIT tutorial.¶
The lessons of this tutorial are aimed at teaching the use of ABINIT, in the UNIX/Linux OS and its variants (MacOSX, AIX …). They might be used for other operating systems, but the commands have to be adapted.
At present, more than thirty lessons are available. Each of them is at most two hours of student work. Lessons 14 cover the basics, other lectures are more specialized. There are dependencies between lessons. The following schema should help you to understand these dependencies.
The “base” lessons are presented at the top, in orange. The blocks in red represents additional lessons related to groundstate features. Responsefunction features are explained in the lessons in the light brown blocks. Finally, the ManyBody Perturbation Theory capabilities are demonstrated in the lessons belonging to the dark brown blocks. The righthand side blocks gather the lessons related to the parallelism inside ABINIT.
Before following the tutorials, you should have read the new user’s guide, as well as the pages 10451058 of Rev. Mod. Phys. 64, 1045 (1992). If you have more time, you should browse through the Chaps. 1 to 13, and appendices L and M of the book this book by R. M. Martin. The latter reference is a must if you have not yet used another electronic structure code or a Quantum Chemistry package.
After the tutorial, you might find it useful to learn about the test cases contained in the subdirectories of ~abinit/tests/, e.g. the directories fast, v1, v2, … , that provide many example input files. You should have a look at the README files of these directories.
Brief description of each lesson’s content¶
I. The lessons 14 present the basic concepts, and form a global entity: you should not skip any of these.

The lesson 1 deals with the H2 molecule: get the total energy, the electronic energies, the charge density, the bond length, the atomisation energy

The lesson 2 deals again with the H2 molecule: convergence studies, LDA versus GGA

The lesson 3 deals with crystalline silicon (an insulator): the definition of a kpoint grid, the smearing of the cutoff energy, the computation of a band structure, and again, convergence studies …

The lesson 4 deals with crystalline aluminum (a metal), and its surface: occupation numbers, smearing the FermiDirac distribution, the surface energy, and again, convergence studies …
Other lessons present more specialized topics.
II. There is a group of lessons that can be started without any other prerequisite than the lessons 1 to 4, and that you can do in any order (there are some exceptions, though):

The lesson on spin in ABINIT presents the properties related to spin: spinpolarized calculations and spinorbit coupling.

The lesson on the use of PAW (PAW1) presents the ProjectorAugmented Wave method, implemented in ABINIT as an alternative to normconserving pseudopotentials, with a sizeable accuracy and CPU time advantage.

The lesson on the generation of PAW atomic data files (PAW2) presents the generation of atomic data for use with the PAW method. Prerequisite: PAW1.

The lesson on the validation of a PAW atomic datafile (PAW3) demonstrates how to test a generated PAW dataset using ABINIT, against the ELK allelectron code, for diamond and magnesium. Prerequisite: PAW1 and PAW2.

The lesson on the properties of the nuclei shows how to compute the electric field gradient. Prerequisite: PAW1.

The lesson on Wannier90 deals with the Wannier90 library to obtain Maximally Localized Wannier Functions.

The lesson on polarization and finite electric field deals with the computation of the polarization of an insulator (e.g. ferroelectric, or dielectric material) thanks to the Berry phase approach, and also presents the computation of materials properties in the presence of a finite electric field (also thanks to the Berry phase approach).

The lesson on electronpositron annihilation shows how to perform TwoComponent DensityFunctional Theory (TCDFT) calculations in the PAW framework to obtain the positron lifetime in the perfect material, the lifetime of a positron localized in a vacancy, the electronpositron momentum distribution wavefunctions and densities.

The lesson on Analysis Tools deals with the use of the CUT3D utility to analyse wavefunctions and densities.

The lesson on the fold2bloch postprocessor deals with the use of the fold2Bloch utility to unfold band structures from supercell calculations.

The lesson on DFT+U shows how to perform a DFT+U calculation using ABINIT, and will lead to compute the projected DOS of NiO. Prerequisite: PAW1.

The lesson on DFT+DMFT shows how to perform a DFT+DMFT calculation on SrVO3 using projected Wannier functions. Prerequisite: DFT+U.

The lesson on the calculation of effective interactions U and J by the cRPA method shows how to determine the U value with the constrained Random Phase Approximation using projected Wannier orbitals. Prerequisite: DFT+U.

The lesson on the determination of U for DFT+U shows how to determine the U value with the linear response method, to be used in the DFT+U approach. Prerequisite: DFT+U.

The lesson on TDDFT deals with the computation of the excitation spectrum of finite systems, thanks to the TimeDependent Density Functional Theory approach, in the Casida formalism.

The lesson “Source code” introduces the user to the development of new functionalities in ABINIT: in this lesson, one learns how to add a new input variable …
III. There is an additional group of lessons on densityfunctional perturbation theory (phonons, optics, dielectric constant, electronphonon interaction, elastic response, nonlinear optics, Raman coefficients, piezoelectricity …), for which some common additional information are needed:

The lesson DFPT 1 (RF1  response function 1) presents the basics of DFPT within ABINIT. The example given is the study of dynamical and dielectric properties of AlAs (an insulator): phonons at Gamma, dielectric constant, Born effective charges, LOTO splitting, phonons in the whole Brillouin zone. The creation of the “Derivative Data Base” (DDB) is presented.

The lesson DFPT 2 (RF2  response function 2) presents the analysis of the DDBs that have been introduced in the preceeding lesson RF1. The computation of the interatomic forces and the computation of thermodynamical properties is an outcome of this lesson.
The additional information given by lesson DFPT1 opens the door to:
 The lesson on Optic, the utility that allows to obtain the frequency dependent linear optical dielectric function and the frequency dependent second order nonlinear optical susceptibility, in the simple “SumOverState” approximation.
The additional information given by lesson DFPT1 and DFPT2 opens the door to a group of lessons that can be followed independently of each other:

The lesson on the electronphonon interaction presents the use of the utility MRGKK and ANADDB to examine the electronphonon interaction and the subsequent calculation of superconductivity temperature (for bulk systems).

The lesson on temperature dependence of the electronic structure presents the computation of the temperature dependence of the electronic structure, the zeropoint motion effect, the lifetime/broadening of eigenenergies.

The lesson on the elastic properties presents the computation with respect to the strain perturbation and its responses: elastic constants, piezoelectricity.

The lesson on static nonlinear properties presents the computation of responses beyond the linear order, within DensityFunctional Perturbation Theory (beyond the simple SumOverState approximation): Raman scattering efficiencies (nonresonant case), nonlinear electronic susceptibility, electrooptic effect. Comparison with the finite field technique (combining DFPT calculatons with finite difference calculations), is also provided.
IV. There is another additional group of lessons on manybody perturbation theory (GW approximation, BetheSalpeter equation), to be done sequentially):

The first lesson on GW (GW1) deals with the computation of the quasiparticle band gap of Silicon (semiconductor), in the GW approximation (much better than the KohnSham LDA band structure), with a plasmonpole model.

The second lesson on GW (GW2) deals with the computation of the quasiparticle band structure of Aluminum, in the GW approximation (so, much better than the KohnSham LDA band structure) without using the plasmonpole model.

The lesson on the BetheSalpeter Equation (BSE) deals with the computation of the macroscopic dielectric function of Silicon within the BetheSalpeter equation.
V. Concerning parallelism, there is another set of specialized lessons. For each of these lessons, you are supposed to be familiarized with the corresponding tutorial for the sequential calculation.

An introduction on ABINIT in Parallel should be read before going to the next lessons about parallelism. One simple example of parallelism in ABINIT will be shown.

Parallelism for groundstate calculations, with plane waves presents the combined kpoint (K), planewave (G), band (B), spin/spinor parallelism of ABINIT (so, the “KGB” parallelism), for the computation of total energy, density, and ground state properties

Parallelism based on “images”, e.g. for the determination of transitions paths (NEB or string method), or for PIMD, that can be activated alone, or on top of other parallelisms, e.g. the “KGB” parallelism for force calculations.

Parallelism for groundstate calculations, with wavelets presents the parallelism of ABINIT, when wavelets are used as a basis function instead of planewaves, for the computation of total energy, density, and ground state properties

Parallelism of DFPT calculations you need to be familiarized with the calculation of response properties within ABINIT, see the tutorial DFPT 1 (RF1)

Parallelism of ManyBody Perturbation calculations (GW) allows to speed up the calculation of accurate electronic structures (quasiparticle band structure, including manybody effects).
Note
Note that not all features of ABINIT are covered by these tutorials. For a complete feature list, please see the Topics page. For examples on how to use these features, please see the ~abinit/tests/* directories and their accompanying README files.