Preview release of the density-functional toolkit (DFTK)

As part of my research stay at the Matherials team of ENPC Paris Tech and Inria I have been developing the density-functional toolkit, DFTK.jl, together with Antoine Levitt and Eric Canc├Ęs. Finally after about six months of joint effort on this Julia code, we just released a first preview in the form of version 0.0.1.

As I mentioned already in previous articles and talks the aim of DFTK is to bridge between mathematicians, computer scientists and materials scientists and to simplify mathematically-motivated research in this interdisciplinary subject. Currently we exclusively focus on a plane-wave discretisation of density-functional theory (PWDFT) as implemented in plenty of mature packages in the community (Abinit, Quantum Espresso, VASP, ...).

DFTK is mainly born from two realisations: Firstly, existing PWDFT progams have huge code bases, where reducing or altering the physical model to a case, which can be treated with rigorous mathematics is very challenging. As a result mathematical research is done in custom codes developed mostly for the purpose of a single project or research questions and findings hardly make it into a setting useful for practitioners. Secondly, such single-purpose custom codes are usually are not fast enough to treat the setting of real-world applications. This prevents verification of obtained results in the context actually relevant in practice. With DFTK we want to overcome this issue by allowing in one code to both implement toy problems and upscale them to the high-performance level needed in practice.

As of now, we're certainly not fully there, but given the short time, we're still proud of our feature list:

  • Plane-wave basis sets
  • All LDA and GGA functionals from libxc
  • Modelling of Insulators and metals (Fermi-Dirac or Methfessel-Paxton smearing)
  • GTH or HGH Pseudopotentials
  • Exploitation of Brillouin zone symmetry for k-Point sampling
  • Band structure computation
  • Full access to intermediate quantities (density, Bloch wave)
  • Three SCF algorithms (DIIS, NLsolve, damping)
  • Close agreement with Abinit for a few thoroughly tested cases (silicon, graphite, manganese).
  • Support for both single and double precision throughout the library for a small set of functionals. Support for arbitrary floating point types is on the way.

Recently we moved the code to JuliaMolSim a github organisation, where we want to collect Julia codes for performing molecular simulations in quantum chemistry and materials science. Along with this we registered the release with the MolSim Julia registry, which means that you can install DFTK by two simple steps:

  1. Add the MolSim registry to your Julia installation. Type from a Julia REPL:
] registry add https://github.com/JuliaMolSim/MolSim.git
  1. Install DFTK as usual, again from a REPL:
] add DFTK

For the time being, DFTK will probably stay in the pre-release stage, as we are not yet completely happy with the internal code structure and the API and we think some more restructuring should follow. Still, we consider the code now sufficiently advanced to suggest you to have a look and try it out :). With this naturally comes a small plea: If you discover something, which bothers you or something, which does not work, please open an issue on github and pose it for discussion. Also we are very happy if you want to contribute something, please just get going!

For further details and the DFTK source code, see the DFTK project page on github. Citations to the DFTK source code are possible using DOI 10.5281/zenodo.3541724.