0 - Choose dispersion for the DOS smearing

Here lev00 allows you to choose a reasonable dispersion $\sigma$ for your DOS smearing and the parameter $\gamma$ which controls the bands broadening, see Eq. (3.9). A menu which opens here is this:

..............MENU DOS - check SMEARING ...........

..... Change these parameters if necessary:...

______________> DOS + Smearing <_______________

0. THE CURRENT PICTURE IS: 1

1. Maximum energy step for the plotting: 0.10000

2. Smeared DOS/LDOS: ENABLED fast method

3. Broaden band boundaries by 1.500 dispersions

4. Number of dispersions to be examined: ... undefined ...

7. Adopt present setting and calculate DOS

10. Preview the current DOS

11. PostScript file for the current DOS

12. Upper limit to the energy-range of the plot: DISABLED

13. Quit: do not proceed.

---> Choose the item and press ENTER:

You are first asked to choose a set of dispersions $\sigma$ of Eq. (3.9) in option 4. The option will then change. For instance, if three dispersions 0.3, 1.0 and 1.5 are chosen, the option 4 will show as:

4. Number of dispersions to be examined: 3

> Dispersions are:

0.30000 1.0000 1.50000

> Files for the plot: dos.dsp1_1 , ... , dos.dsp3_1

> Files with smearing plot: dos.dsp1_1_ , ... , dos.dsp3_1_

> Names of the PostScript files: dos.dsp1_1.ps , ... , dos.dsp3_1.ps

It now shows all the file names to be produced during the calculation. Note that the first number in any name changes from 1 to 3 (the number of dispersions), while the second one corresponds to the number of the current picture shown under option 0. You can use this latter option to change the picture number in order to produce new files and not to overwrite the existing ones.

The quantity $\gamma$ of Eq. (3.9) is chosen in 3.

When the dispersions are chosen, new options 8 and 9 appear that allow you to preview and save as a postcript file, respectively, each individual DOS as they are being calculated. The corresponding file names are gievn under option 4 as explained above.

As was mentioned in Section 3.4, there are two methods that can be used to calculate the DOS: fast and slow. The fast method for smearing is the default. It is possible to choose between the two methods in option 2.

The calculation of the DOS curves is run by option 7. After running the calculation, you can preview all curves simultaneously together with the raw DOS (no smearing) using 10 as shown in Fig. 3.1.

Figure 3.1: Total DOS for the MgO bulk for three values of the dispersion $\sigma$.

This should allow you to choose the best possible parameters $\sigma$ and $\gamma$ which do not change significantly the structure of the raw DOS curve, and then use them in other DOS options of the main menu of lev00. The appropriate postcript file is produced by 11. Finally, the upper limit for the DOS is controlled by option 12.

Finally, we remark on the energy step of option 1. Normally, the default value of 0.1 eV is fine. The energy step here is needed only as a guidance as the actual step is chosen individually for each physical band to ensure that there are at least 10 points even for very narrow bands.