Last Modified 15 February 2000

The ``Static'' Tight-Binding Program: Example VII -- Output

If you've followed the steps on the setup page, your working directory should now look something like this:

$ ls -l
total 19
-rw-r--r--   2 mike     mike         1380 Jun  1 11:45 SKIN
-r--r--r--   3 mike     mike         7130 May 28 15:14 ag_par
-r--r--r--   3 mike     mike        10003 Jul 28  1997 spcgrp

Now run the static code in this directory. You'll get something like this:

$ ls -l
total 549
-rw-rw-r--   1 mike     mike       428946 Jun  1 21:13 QLMT
-rw-rw-r--   1 mike     mike           63 Jun  1 21:13 SKENG
-rw-r-----   2 mike     mike         1386 Jun  1 17:22 SKIN
-rw-rw-r--   1 mike     mike        46724 Jun  1 21:13 SKOUT
-r--r--r--   3 mike     mike         7130 May 28 15:14 ag_par
-rw-rw-r--   1 mike     mike        59979 Jun  1 21:12 output
-r--r--r--   3 mike     mike        10003 Jul 28  1997 spcgrp

This is where we usually tell you to look at the SKENG file:

 fcc  7.580           108.879878    -.277290679-1452.579026708

This doesn't look right. To find out what is wrong, look at the bottom of the output file:

$ tail -3 output

FERMI:  mu =   -.277291 is the best we can do
 Get N =  5260.00904328 wanted   11.00000000

The program is telling you that the k-point list isn't adequate to calculate the correct number of electrons in the system, much less the total energy. This shouldn't be surprising, because we are only looking at the eigenvalues along a few lines rather than through the entire Brillouin zone. (Also, if you look at the k-point mesh as shown in output or SKOUT you'll see the weights listed as 501. This is a consequence of the along-the-line generating scheme, and is just another warning that you can't use these k-points for Brillouin zone integration.)

The real interest in this static run is the QLMT file. We'll just look at the first k-point from this file:

    1    1    0    1     SPINS, WIND., SC. WIND.
  360 K-POINTS     1  11.00000   0.00200
  0.000000  0.000000  0.000000360.000000         9    0.3600000000D+03 K
-0.2772907   0.000000E+00
    1.000000000    0.000000000    0.000000000    0.000000000
-0.0386601   0.000000E+00
    0.000000000    0.000000000    1.000000000    0.000000000
-0.0386601   0.000000E+00
    0.000000000    0.000000000    1.000000000    0.000000000
-0.0386601   0.000000E+00
    0.000000000    0.000000000    1.000000000    0.000000000
 0.0474658   0.000000E+00
    0.000000000    0.000000000    1.000000000    0.000000000
 0.0474658   0.000000E+00
    0.000000000    0.000000000    1.000000000    0.000000000
 1.7012972   0.000000E+00
    0.000000000    1.000000000    0.000000000    0.000000000
 1.7012972   0.000000E+00
    0.000000000    1.000000000    0.000000000    0.000000000
 1.7012972   0.000000E+00
    0.000000000    1.000000000    0.000000000    0.000000000

use by other programs, not the tight-binding programs we're using here. The second line has the number of k-points (360), the number of atoms in the unit cell (1), the number of electrons in the unit cell (11), and the Fermi broadening temperature (.002) from the SKIN file.

The ``K'' at the end of the next line tells us that this is a new k-point. The first three numbers give the location of the k-point in reciprocal lattice coordinates. The next number is the weight, which would be less than one if this was a Brillouin zone integration mesh rather than a line mesh. The next number (9) is the number of eigenvalues found at this k-point, and the last number is a more precise listing of the weight.

In this example, each of the eigenvalues takes up two lines. The first line has the eigenvalue itself (-.2772907 for the first eigenvalue) and a dinosaur track in the form of a zero. In the Mode=6 version of the QLMT file, each atom gets one line after the eigenvalue. The line represents the s, p, d, and f angular momentum decomposition of the eigenvalue on that electron. This information can be used to construct a local density of states for the atom. We see that the first eigenvalue (-.2772907) is a pure s state, while the triply degenerate state at -.0386601 and the doubly degenerate +.0474658 level are pure d states. At other k-points there will be mixing between the states. (There are no f electrons in our tight-binding scheme, so the last column in each of these lines will always be zero.)

This information is repeated for each eigenvalue and k-point in the calculation.

Go on to plot the band structure or go back and look at the SKIN file setup.

Look at other examples.

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