Producing Green's function for impurity calculation

For the impurity calculation you first have to make a file that contains the data about the positions of atoms which form the "impurity" cluster. This "impurity" cluster then is embedded into the host, and the impurity program recalculates self-consistently the potential, charge density, etc. for the atoms which are inside the impurity cluster, assuming the boundary conditions with the host. The simplest way to make such a file is the following. First make one iteration of the 'tb-kkr' program starting from the self-consistent potential for your system and use the test-option clusters in the inputcard. You will see the text-format file "clusters" which contains the information about tight-binding clusters for all atoms presenting in the inputcard. Then you should choose the site, which will be the center site of the impurity cluster, cut out the data concerning other atoms, and make the "impurity" file (let's call it "scoef") in the format, presented below:

19
0.00000000	0.00000000	0.00000000	3	29.0	0.000000
0.20412415	-0.35355339	-0.57735027	2	29.0	0.707107
-0.40824829	0.00000000	-0.57735027	2	29.0	0.707107
0.20412415	0.35355339	-0.57735027	2	29.0	0.707107
0.00000000	-0.70710678	0.00000000	3	29.0	0.707107
-0.61237244	-0.35355339	0.00000000	3	29.0	0.707107
0.61237244	-0.35355339	0.00000000	3	29.0	0.707107
-0.61237244	0.35355339	0.00000000	3	29.0	0.707107
0.61237244	0.35355339	0.00000000	3	29.0	0.707107
0.00000000	0.70710678	0.00000000	3	29.0	0.707107
-0.20412415	-0.35355339	0.57735027	4	0.0	0.707107
0.40824829	-0.00000000	0.57735027	4	0.0	0.707107
-0.20412415	0.35355339	0.57735027	4	0.0	0.707107
-0.40824829	-0.70710678	-0.57735027	2	29.0	1.000000
0.81649658	0.00000000	-0.57735027	2	29.0	1.000000
-0.40824829	0.70710678	-0.57735027	2	29.0	1.000000
0.40824829	-0.70710678	0.57735027	4	0.0	1.000000
-0.81649658	-0.00000000	0.57735027	4	0.0	1.000000
0.40824829	0.70710678	0.57735027	4	0.0	1.000000

The example, presented here, has been obtained from calculation for Cu (111)-surface using decimation technique with 12 layers slab 3Cu/6Vac/3Cu, and we suppose that one impurity atom is put in the Cu surface layer, which has id-number 3 in the inputcard. The number in the first row of the "scoef" file is the total number of atoms in the cluster, the first three columns are the $(z,y,z)$ coordinates, the id-numbers of the atoms (according to the inputcard) are in the 4-th column, the atomic charges are in the 5-th column, the distances are in the last column.

Then set in the inputcard the correct name (say, "scoef") of the file I25, which you just have created, set IGREEN=1, ICC=1, and make one iteration of the 'tb-kkr' program. You will obtain three files: "impurity.coefs", "intercellref" and "green" (this last file is in the binary format, it has a huge size and contains the information about the structural Green's function $G_{LL'}^{nn'}(E)$ for all sites $n$ and $n'$ of our cluster). Make the new directory for "impurity" calculation in you working directory and copy these 3 files to the new directory.