Common Problems In Generating All Electron Densities And How

Let's begin by taking a look at a typical .ini file:

8.00 1 2 6 0.00 : z nc nv
1 0 2.00 : n l f
2 0 2.00
2 1 4.00
3 "t" : lmax s_pp_def
0 0.0 0 "t"
1 0.0 0 "t"
2 0.0 0 "t"
3 0.0 0.01 "t"

The above file is that of neutral oxygen. We extract the .ae file using the generated fort.19 and fort.25 files generated by the fhi code, where these are the core and valence densities respectively. In the case of atoms that only have electrons in the 1s orbital, only a fort.19 file will be generated, therefore a different perl script, extract_ae_nocore.pl, must be used to generate the .ae file. The syntax is the same as for extract_ae.pl. Note: If you wish to make .ae files for H1 or other atoms with zero electrons, you must leave 0.0001 electrons, or some other small number, remaining in the lowest energy slot, as a .ae file cannot be generated with zero electrons present.

The most common problems arise from the presence of everything after the 3 "t", and can be resolved by simply deleting this section. Note that there is no benefit from keeping this part of the file in. It can only cause problems, therefore, to be safe, it should always be removed.

Another problem often arises in the case of negative ions. This can be fixed by classifying up spin and down spin electrons separately, which would make the above file look like this:

8.00 1 2 6 0.00 : z nc nv
1 0 1.00 1.00 : n l f
2 0 1.00 1.00
2 1 2.00 2.00
3 "t"

In the case of an odd number of electrons in the final orbital, putting the last electron in the left or right column makes no difference.

The final problem that we have encountered arrises when an additional orbital is required to accomodate the excess electrons for an ion of large negative charge. The tags "nc" and "nv" that refer to the second and third numbers on the first line stand for "number of core states" and "number of valence states" respectively. When a new state is added, increase the nv number by one. You may wonder why this new state is automatically as a valence state, and why the classifications of other states automatically remain the same, however which states are designated as core and which as valence only matters when generating pseudopotentials. Since we are making files which contain all of the electrons, all that matters to us is that the total number of states equals nc + nv, and therefore these concerns are irrelevant.

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