Introduction
This Tutorial Review provides a concise introduction to some practical aspects of running Kohn–Sham density functional theory (KS-DFT) calculations. It is intended as a guide for non-experts, students, occasional practitioners, or anyone that wants to start its own adventures in the “zoo” of DFT approximations. It is organized in three parts. In the first part, we answer a few questions to establish a necessary (but far from sufficient) foundation. In the second part, we concentrate on the methodological components and we introduce the discussion on the choice of the functional and basis set. In the third part, we deal with some technical issues that are important for the reliability and reproducibility of calculations. The purpose of this tutorial is to draw awareness to the details, rather than being a comprehensive guide for all DFT-related answers. To this extent, it represents a complementary tutorial to other that have appeared in this series, in particular to the foundational essay by K. Burke and L. O. Wagner entitled “DFT in a Nutshell”.1 Because of its general audience, the technical details of the reported issues have been simplified to some degree. To make up for it, we provide a broad body of references where the interested readers can find the important technicalities of each discussed topic. This review is also accompanied by a notebook of 12 calculation experiences, which is formatted for students of an advanced undergraduate or graduate course, but it is challenging enough to be interesting for more experienced users as well.