MedeA-ElectrA

Method and Scope

ElectrA is a speed-efficient all-electron density functional electronic structure code based on the augmented spherical wave (ASW) method and the atomic sphere approximation (ASA).

One of ElectrA's merits is its fast performance when computing properties that derive directly from the energy bands and the one-electron wave functions. In particular, this applies to Fermi surface properties and optical properties where ElectrA scales linearly with the number of k-points included in a calculation.

Because of its state-of-the-art implementation, the ASA approximation and the use of the Anderson/Broyden charge density mixing, ElectrA is very fast and therefore is the code of choice wherever this approximation is justified [1,2].

Features

	Self-consistent all-electron density functional method using the local (spin) density approximation
	Local density approximation (LDA) and generalized gradient approximation [*] (GGA)
	Full coverage of periodic table
	Semirelativistic (ie. includes mass-velocity and Darwin shifts)
	Spin-polarized treatment of magnetic systems
	Best suited for close-packed materials
	Automated empty spheres construction for treating semi-open structures [3]
	Anderson/Broyden charge density mixing [4]
	Total energies, bulk moduli [*]
	Band structure (spin restricted and spin unrestricted)
	Site-, spin- and partial-wave projected densities of states
	Magnetic moments
	Core level spectra [*]
	Charge and spin densities at the nuclei, isomer shifts, hyperfine fields [*]
	Optical spectra (ie. calculation of optical matrix elements and generation of spectra)
	High computational efficiency (for example, the self consistent electronic structure calculation including band structures, densities of states and optical spectra for TiAl takes about 150 seconds on a laptop with a 350 MHz processor and 64 MB of RAM)

                                                                                                                             [*] in preparation

Application Example 

Electronic structure of CaTiO3 - Calculation of energy ands, density of states, partial atomic charges, optical spectra

	k-mesh for SCF: 0.2/Ang
	k-mesh for DOS:0.1/Ang
	k-mesh for optical run: 0.1/Ang

Total compute time: < 2 min

The results were viewed interactively within MedeA. The crystal structure (shown on the right) was rendered via ray-tracing (POV-Ray). Total computing time: 120 seconds with a 450 MHz Pentium II under Windows® 98.

References

• Volker Eyert, "Basic notions and applications of the augmented spherical wave method", Int. J. Quant. Chem. 77, 1007-1031 (2000), Special Issue: "Electronic Structure of Materials", edited by M. Defranceschi.
  

• ASW Homepage, Volker Eyert and Karl-Heinz Höck,
  "The electronic structure of V₂O₅: Role of octahedral deformations",
  Phys. Rev. B 57, 12727-12737 (1998).
  

• Volker Eyert, "A comparative study on methods for convergence acceleration of iterative vector sequences", J. Comput. Phys. 124, 271-285 (1996).
  
  

• Comprehensive list of ASW Publications

• J. Kübler and V. Eyert,  "Electronic structure calculations"
  in: "Electronic and Magnetic Properties of Metals and Ceramics", edited by K. H. J. Buschow (VCH Verlagsgesellschaft, Weinheim, 1992), pp. 1-145;
  Volume 3A of "Materials Science and Technology - A Comprehensive Treatment", edited by R. W. Cahn, P. Haasen, and E. J. Kramer (VCH Verlagsgesellschaft, Weinheim, 1991-1996).

• Volker Eyert, "Electronic structure calculations for crystalline materials,
  in: Density Functional Methods: Applications in Chemistry and Materials Science", edited by M. Springborg (Wiley, Chichester, 1997), pp. 233-304.

• Volker Eyert and Ulrich Eckern, "Bandstruktur - Von der Quantenmechanik zum Materialdesign", Physik in unserer Zeit 31, 276-282 (2000).