NELECT and the neutralizing background

[user]

Dear All,

In the Guide, it is said that "If the number of electrons is not compatible with the number derived from the valence and the number of atoms a homogeneous background-charge is assumed.", see: http://cms.mpi.univie.ac.at/vasp/vasp/node130.html

I am wondering if the contribution from the background charge is included in the total energy printed at the end of the OUTCAR?

Also from the Guide: "If the number of ions specified in the POSCAR file is 0 and NELECT=n, then the energy of a homogeneous LDA-electron gas is calculated."

I have tried to set the number of ions in POSCAR equal to 0 and calculate the energy of the homogeneous LDA-electron gas (the neutralizing background charge?), but it doesn't work. The error message was something like: forrtl: severe (174): SIGSEGV, segmentation fault occured.

Hope you could help.

Thanks.

[admin]

--) this depends on whether you include the corrections.
--) to calculate the homogeneous electron gas, you have to use a special PP (not provided via the ftp server)

[user]

Dear Admin,

--) this depends on whether you include the corrections.

So, the neutralizing background is not included by default or the contribution from the neutralizing background (the "corrections", as you said) is not printed out? How can we include?

--) to calculate the homogeneous electron gas, you have to use a special PP (not provided via the ftp server)

Can we ask for this PP if we really need it?

Another question:

Can we use NELECT, FERWE, FERDO tags to remove/add electron(s) from/to a specific orbital/atom (i.e., by controling the total number of electrons and the occupation number at a specific orbital)? How good/bad is this idea, physically?

Thank you very much.