Last Modified 17 December 1999
Using the information from the previous page, we are now ready to set up the SKIN file for this problem. The following discussion assumes that you have compiled the static source as outlined in the Installation notes, and that you have copied the following files into your working directory:
-r--r--r-- 2 mehl mehl 7349 May 25 13:12 au_par_99 -r--r--r-- 1 mehl mehl 12095 May 6 13:51 kpts.r24 -r--r--r-- 1 mehl mehl 92560 May 6 14:21 kpts.r48 -r--r--r-- 1 mehl mehl 881 May 6 13:33 spcgrp
where au_par_99 is our good (but unpublished) set of Gold parameters. These parameters are rather short-range, and seem to be pretty stable.
The top of the SKIN file then looks like this:
Mode=1 (Calculate E(V) and P(V))
0.005 1.000 (T_{Fermi}, Eigenvalue cutoff for P calculation)
au_par
We have chosen to use Mode 1, the Gillan extrapolation of the total energy to zero temperature. For these kinds of problems T = 5 mRy is an adequate temperature (the cutoff doesn't matter as we are not calculating a pressure). We also, of course, list the parameter file.
For our first structure we choose a rather small q: <111> Au 12 layer Stacking Fault -- lambda = -0.545454545454545
-0.545454545454545 (label for SKENG, == q) 0.00 (Electrons in addition to nominal Au charge (=11/atom)) 0 (Lattice 0, specify all vectors + scaling) 0.0000000000 3.8550410000 3.8550410000 3.8550410000 0.0000000000 3.8550410000 29.4384949091 29.4384949091 -33.6439941818 1.0000000000 1.0000000000 1.0000000000 0 (No additional strains applied)
The system is neutral, so there are no extra electrons floating about. According to the Lattice Types page, for type zero we specify the entire lattice plus three scaling factors. The lattice specified on the unit cell page is not one of the other more speciallized lattices, so we must use this form. We could have divided everything by the lattice constant a and scaled, but this way works, too. Note that 7.710082 Bohr = 4.08 Angstroms is the experimental lattice constant of gold.
The next part of the SKIN file tells us a little bit more about the lattice:
0 (No additional strains applied) 12 (Atoms in the unit cell) 6 6 1 (Neighbor search cutoff indicies) F (Logical variable -- no internal displacements)
We are not applying any external strains to the lattice, so the first line of this section is zero. We know that there are 12 atoms in the unit cell.
In the search string, we know that the length of a3 is substantially larger than the cutoff length, which here is 12.5 Bohr. Therefore we only need to look into the next unit cell in this direction. In the other directions we look out to six unit cells so that we will not miss anything in the case of extreme values of q.
Finally, the F line indicates that we are putting no other strains on the atoms. (This line leads to a section of the code which is projected to be used in phonon calculations, but has not been completely implemented.)
The next 12 lines are the atoms:
-1 0.0000000000 0.0000000000 0.0000000000 0 0 0 -1 3.8550410000 3.8550410000 0.0000000000 0 0 0 -1 7.7100820000 7.7100820000 0.0000000000 0 0 0 -1 7.7100820000 7.7100820000 -7.7100820000 0 0 0 -1 11.5651230000 11.5651230000 -7.7100820000 0 0 0 -1 15.4201640000 15.4201640000 -7.7100820000 0 0 0 -1 15.4201640000 15.4201640000 -15.4201640000 0 0 0 -1 19.2752050000 19.2752050000 -15.4201640000 0 0 0 -1 23.1302460000 23.1302460000 -15.4201640000 0 0 0 -1 23.1302460000 23.1302460000 -23.1302460000 0 0 0 -1 26.9852870000 26.9852870000 -23.1302460000 0 0 0 -1 30.8403280000 30.8403280000 -23.1302460000 0 0 0
Note that we are using the "-" option (see Example 11) to tell the program that the atomic positions of these atoms are given in Cartesian coordinates (which don't change inside the first primitive unit cell) instead of lattice coordinates (which would change with q).
Finally, we have the k-point section. We us the space group and k-point files found on the previous page:
NEWSYM=T (Generate new set of k-points) LATTIC=1 (Lattice type / Next is spacegroup file name:) spcgrp ILAT=F (Space group file in Cartesian Coordinates) -1313 kpts.r48
this example uses the large k-point mesh. You can also use the small k-point mesh by changing "r48" to "r24".
The rest of the structures are similar to the above. For example, for q = -½ we have:
<111> Au 12 layer Stacking Fault -- lambda = -0.50 -0.50 (label for SKENG, == q) 0.00 (Electrons in addition to nominal Au charge (=11/atom)) 0 0.0000000000 3.8550410000 3.8550410000 3.8550410000 0.0000000000 3.8550410000 29.5553143333 29.5553143333 -33.4103553333 1.0000000000 1.0000000000 1.0000000000 0 (No additional strains applied) 12 (Atoms in the unit cell) 6 6 1 (Neighbor search cutoff indicies) F (Logical variable -- no internal displacements) -1 0.0000000000 0.0000000000 0.0000000000 0 0 0 -1 3.8550410000 3.8550410000 0.0000000000 0 0 0 -1 7.7100820000 7.7100820000 0.0000000000 0 0 0 -1 7.7100820000 7.7100820000 -7.7100820000 0 0 0 -1 11.5651230000 11.5651230000 -7.7100820000 0 0 0 -1 15.4201640000 15.4201640000 -7.7100820000 0 0 0 -1 15.4201640000 15.4201640000 -15.4201640000 0 0 0 -1 19.2752050000 19.2752050000 -15.4201640000 0 0 0 -1 23.1302460000 23.1302460000 -15.4201640000 0 0 0 -1 23.1302460000 23.1302460000 -23.1302460000 0 0 0 -1 26.9852870000 26.9852870000 -23.1302460000 0 0 0 -1 30.8403280000 30.8403280000 -23.1302460000 0 0 0 NEWSYM=F
The only changes are the label, the value of q, and the lattice resulting from this q. The k-point mesh is the same as in the previous entry, so we just use NEWSYM=F to indicate this. The process is then repeated for every value of q we want to use.
We save the entire SKIN file in our working directory, which now looks like this:
-r--r--r-- 1 mehl mehl 53217 May 25 20:12 SKIN -r--r--r-- 2 mehl mehl 7349 May 25 13:12 au_par_99 -r--r--r-- 1 mehl mehl 12095 May 6 13:51 kpts.r24 -r--r--r-- 1 mehl mehl 92560 May 6 14:21 kpts.r48 -r--r--r-- 1 mehl mehl 881 May 6 13:33 spcgrp
And now we are ready to run the job.
Previous: Setting up the unit cell
Next: Running the Job
Look at other examples.
Get other parameters from the Tight-binding periodic table.
Return to the static Reference Manual.