Spring School Computational Tools: Day 3 – Abinit

Today is the third day of our spring school. After the introduction to VASP yesterday, we now turn our attention to another quantum mechanical level solid state code: ABINIT. This is a Belgian ab initio code (mainly) developed at the Université Catholique de Louvain (UCL) in Wallonia.

Since no-one at CMM has practical experience with this code and several of us are interested to learn more about this code, we were very pleased that the group of Prof. Xavier Gonze was willing to support this day in its entirety. During the morning introductory session Prof. Xavier Gonze introduced us into the world of the ABINIT code, for which the initial ideas stem from 1997. Since then, the program has grown to about 800.000 lines of fortran code(!) and a team of 50 people worldwide currently contribute to its development. Also in recent years, a set of python scripts have been developed providing a more user friendly interface (abipy) toward the users of the code. The main goal of the development of this interface, is to shift interest back to the physics instead of trying to figure out which keywords do the trick. We also learned that the ABINIT code is strongly inspired by the ‘free software’ model, and as such Prof. Xavier Gonze prefers to refer to the copyright of ABINIT as copyleft. This open source mentality seems also to provide strength to the code; leading to its large number of developers/contributors; which in turn leads to the implementation of a wide variety of basis-sets, functionals and methodologies.

After the general introduction, Dr. Matteo Giantomassi introduced the abipy python package. This package was especially developed for automating post-processing of ABINIT results, and automatically generating input files. In short, to make interaction with ABINIT easier. Matteo, however, also warned that this approach which makes the use of ABINIT much more black box, might confuse beginners, since a lot of magic is going on under the hood of the abipy scripts. However, his presence, and that of the rest of the ABINIT delegation made sure confusion was kept to a minimum during the hands-on sessions, for which we are very grateful.

After the lunch break, Prof.  Gian-Marco Rignanese and Prof. Xavier Gonze held a duo seminar on more advanced topics covering Density Functional Perturbation Theory and based on this spectroscopy and phonon calculations beyond the frozen phonon approach. Of these last aspects I really am interested in seeing how they cope with my Metal Organic Frameworks

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