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Manuscript Title: Full-potential, linearized augmented plane wave programs for crystalline systems.
Authors: P. Blaha, K. Schwarz, P. Sorantin, S.B. Trickey
Program title: WIEN
Catalogue identifier: ABRE_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 59(1990)399
Programming language: Fortran.
Computer: IBM 3090-400E/2VF.
Operating system: IBM VM/XA, IBM MVS/XA.
RAM: 6900K words
Word size: 64
Keywords: Solid state physics, Crystals, Linearized augumented Plane wave (lapw) method, Full-potential lapw (f-lapw), Energy, Band structure, Local spin density Functional calculations, Electric field gradient, Electronic charge (spin) densities, Total energy.
Classification: 7.3.

Nature of problem:
Calculation of spin densities, total energy, Kohn-Sham energy bands, and electric field gradients at nuclear sites, for various local density approximations in a broad variety of crystalline space groups, with or without relativistic corrections, with the full potential or in the muffin-tin approximation.

Solution method:
Kohn-Sham orbitals are expanded in a Linearized Augmented Plane Wave basis set to construct the generalized secular equation (i.e. including the basis set overlap matrix) from a starting potential which is the superposition of atomic potentials truncated at the muffin-tin radii (radii of non-overlapping spheres centered at each nuclear site). Diagonalization yields the first N eigenvalues and eigenvectors at each k-point in the irreducible wedge of the Brillouin zone. Spin densities are then constructed. From them new potentials (as spherical plus non- spherical parts in each muffin-tin sphere and as Fourier series in the interstitial region) are obtained by a combination of multipolar, Fourier, and numerical techniques to solve Poisson's equation. A new secular matrix is then generated. The cycle is repeated until self-consistency is attained. Iterative stability is enhanced by mixing densities from one or more previous iterations. Both straight mixing and the Broyden II scheme are provided. Relativistic corrections can be included fully for core states and approximately (scalar-relativistic corrections) for valence states. Calculation in the muffin-tin approximation may be elected either for testing or for comparison with older literature.

Restrictions:
Cubic, tetragonal, orthorhomic, and hexagonal space groups with inversion symmetry are implemented currently. Space groups within these restrictions may be handled by construction of suitable input, the procedure for which is summarized in the User's Guide. Treatment of groups of lower symmetry would require recoding. To handle cases without inversion symmetry, Hermitian matrices would be needed in place of the real symmetric ones now assumed. Extension to structures without rectangular basis vectors would require a consistent representation in cartesian coordinates throughout the programs, so reprogramming analogous with the existing treatment of hexagonal structures would be required.

Unusual features:
The package consists of six program modules among which data can be routed according to choice of EXEC's and files to achieve whatever goal (e.g. core, semi-core, or valence state, total energy or not, etc.) the user has at that time. File editing between modules is not required. All modules have been tested extensively in the IBM 3090VM and MVS environments and refined to utilize IBM XA virtual addressing and the Vector Feature for sustained high performance.

Running time:
Li in the bcc phase with 91 k points in the irreducible wedge of the Brillouin Zone, maximum angular momentum parameter L = 12, and the longest wave vector Kmax of the plane waves chosen such that Rt * Kmax = 8.00 (with Rt the muffin-tin radius), requires six iterations and a total of 766 seconds on a single processor of a base model IBM 3090-400/ VF under MVS/XA.