# What is the RWIGS value for the DOS calculation in VASP?

I want to set the RWIGS value in the INCAR file for the investigation of the density of states (DOS) of $$\ce{Mg2Si}$$ so what should be the value of RWIGS and LORBIT as well for DOS?

For calculating DOS in VASP, Relaxed the structure first using ISIF=3 (volume and atom position relaxation) followed by SCF calculation for generating charge density.

In the third calculation use LORBIT=11/12 with ISTART=11. VASP ignores RWIGS parameter for LORBIT>=10,hence no need to change that.

Use the ISMEAR parameter wisely.

• +1. Please take a close look at the edits I did though, so that no one has to do those in the future for you. Also we have a VASP chatroom: chat.stackexchange.com/rooms/109983/vasp, can you say "hello" at least once so that we can remember later that you're one of the users of VASP? – Nike Dattani Mar 15 at 19:21
• @Pranav thanks for your answer , but if I set LORBIT <10 let's say LORBIT= 5 then what would be the value of RWIGS in this case ? – Shalini Mar 16 at 6:26

What is the RWIGS value for the density of states calculation in VASP?

• In short, RWIGS specifies the Wigner-Seitz radius for each atom type. The default value for this tag can be read from the POTCAR. If you have not any prior knowledge about your system, for example, the charge distribution around each atom, I strongly suggest you just use the default radius. If you do want to know how to set manually it, you may need to understand how the PAW method adopted by the VASP package works.

• Always take a first look at the official explanation about the tag used by INCAR from vaspwiki. For example, you can find an explanation of the RWIGS tag: https://www.vasp.at/wiki/index.php/RWIGS

what should be the value of RWIGS and LORBIT as well for DOS?

• The relation between RWIGS and LORBIT also can be found in vaspwiki.

• If you just want to calculate the DOS, you can simply follow @pranav kumar's strategy:

• Self-consistent-field (SCF) calculation to obtain converged charge density.

• Non-self-consistent-field (NSCF) calculation by reading SCF charge density to calculated DOS.

• The general DOS-related tags used in INCAR:

#DOS-related:
LORBIT=11
#RWIGS=R(Mg) R(Si)    ## fill two real number
EMIN=-20
EMAX=15
NEDOS=2000


Hope it helps.

• thanks for answer I am asking you again what I ahve asked from Pranav Kumar that what if I set LORBIT not equal to 11 i.e LORBIT = 5 for adding RWIGS tag then what should be the value of RWIGS as you mentioned 1.22 , how one can decide on this ? In my POTCAR file there are two values of RWIGS =2.88 and 1.524 which one should I opt ? – Shalini Mar 16 at 14:16
• @Shalini I have edited my answer about the setting for the RWIGS tag in your system. You can just fill two real numbers between the two radius given by POTCAR and test what will happen. I have no idea about what the reasonable radius should be, as claimed in my post. – Jack Mar 17 at 1:34