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Manuscript Title: A subroutine package for computing Green's functions of relaxed surfaces by the renormalization method.
Authors: J. Henk, W. Schattke
Program title: GREEN
Catalogue identifier: ACNU_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 77(1993)69
Programming language: Fortran.
Computer: CRAY X-MP.
Operating system: UNICOS, CONVEXOS, VMS, MS-DOS.
RAM: 5000K words
Word size: 64
Keywords: Solid state physics, Crystal field, Green's functions of Reconstructed Semi-infinite solids, Renormalization.
Classification: 7.3.

Nature of problem:
In the determination of the electronic structure of semi-infinite solids the Green's function is the essential quantity from which the layer- resolved density of states, electron density and other properties may be derived. Its computation is complicated because of the truncation of the solid by the surface, for example computation schemes used for bulk crystals are impractible.

Solution method:
The layer-resolved Green's function is determined via the renormal- ization method [1] in the case of models with a localized basis set, e.g. tight-binding models. The effective interlayer interaction is iteratively reduced to zero by combining adjacent crystal layers. This highly convergent procedure leads to layer diagonal blocks of the Green's function matrix of both bulk and surface. Other blocks are accessible by means of transfer matrices.

Restrictions:
The solid under consideration must have lattice periodicity parallel to the surface. The interaction between basis states must have a finite interaction radius.

Unusual features:
None.

Running time:
0.2 seconds per energy and parallel component of the wavevector for GaAs(110)1x1 with matrix dimension 32x32.

References:
[1] M.P. Lopez Sancho, J.M. Lopez Sancho, and J. Rubio, J. Phys.F: Metal Physics 15(1985)851.