Elk Code

Elk code: elk.sourceforge.net

Highly efficient nature of the Kohn-Sham equations within density functional theory (DFT), and ever-increasing computer power has made electronic structure of complex systems easily accessible. DFT codes are routinely used for materials search and design, before performing actual expensive experiments. A reliable theory of ground-state properties is thus a key requirement for tailoring future materials and this in turn requires highly accurate numerical codes. There are several computer codes capable of calculating ground-state or excited state properties, but only a few of them are of the highly accurate all-electron kind, which treat all the electrons in the solid on the same footing. Elk is one such highly accurate all-electron full-potential linearized augmented-plane wave (FP-LAPW) code with many advanced features, and which has been in development now for 15 years. It is released under the GNU General Public License (GPL), so as to encourage scrutiny of the code itself, free development of new techniques. What sets Elk code apart from its contemporaries is

  • all-electron APW for highest accuracy calculations: this includes a flexible basis, which in addition to APW also includes local-orbitals of different kinds.
  • Highly general treatment of spins: magnetization is treated as a free vector field allowing for non-collinear magnetic systems including spin-spiral states.
  • Interface to the ETSF exchange-correlation library libxc making available almost every local density approximation (LDA) and generalized gradient approximation (GGA) functional ever invented.
  • Calculation of phonon dispersions and electron-phonon coupling parameters.
  • The only solid state code capable of calculating ground state properties and spectra using one-body reduced density matrix functional theory (RDMFT).
  • Linear and non-linear optical spectroscopy with in random phase approximation; sophisticated calculation of linear optical spectra by solving linear response time-dependent density functional theory (TDDFT) equation using various exchange-correlation kernels as well as by solving the Bethe-Salpeter equation (BSE).
  • The only code capable of real time propagation for extended systems.
  • The only solid state code capable of real-time dynamics of spins and charge under strong electro-magnetic field
  • and most importantly in addition to being user friendly, it is highly developer friendly -- new ideas within the field of DFT can easily be implemented within Elk