# DFTK.jl: The density-functional toolkit.

The density-functional toolkit, DFTK for short, is a library of Julia routines for playing with plane-wave density-functional theory (DFT) algorithms. In its basic formulation it solves periodic Kohn-Sham equations. The unique feature of the code is its emphasis on simplicity and flexibility with the goal of facilitating methodological development and interdisciplinary collaboration. In about 5k lines of pure Julia code we already support a sizeable set of features, after just a good year of development. Our performance is of the same order of magnitude as much larger production codes such as Abinit, Quantum Espresso and VASP.

## Package features

• Methods and models:
• Kohn-Sham-like models, with an emphasis on flexibility: compose your own model, from Cohen-Bergstresser linear eigenvalue equations to Gross-Pitaevskii equations and sophisticated LDA/GGA functionals (any functional from the libxc library)
• Analytic potentials or Godecker norm-conserving pseudopotentials (GTH, HGH)
• Brillouin zone symmetry for k-Point sampling using spglib
• Smearing functions for metals
• Collinear spin polarization for magnetic systems
• Self-consistent field approaches: Damping, Kerker mixing, Anderson/Pulay/DIIS mixing
• Direct minimization
• Multi-level threading (kpoints, eigenvectors, FFTs, linear algebra)
• MPI-based distributed parallelism (distribution over kpoints)
• 1D / 2D / 3D systems
• Magnetic fields
• Treat systems beyond 500 electrons
• Ground-state properties and post-processing:
• Total energy
• Forces
• Density of states (DOS), local density of states (LDOS)
• Band structures
• Support for arbitrary floating point types, including Float32 (single precision) or Double64 (from DoubleFloats.jl). For DFT this is currently restricted to LDA (with Slater exchange and VWN correlation).
These and more examples can be found in the examples directory of the main code.