# How to set different exchange correlational functionals in VASP?

I want to test different exchange correlational functional on Magnesium silicide to investigate the electronic properties. For example, if I have the POTCAR library for various pseudopotentials of Mg and Si where we can specify the type of functional from the title/header let's say PBE. How can I change this PBE to PW91 in INCAR to see the effect? The following screencast is my INCAR for structure relaxation.

Thanks!

• In the future, please don't add additional questions as new answers. If it is a minor addition, you can edit it into the original question. For larger changes, generally you should create a brand new question.
– Tyberius
Mar 15 at 17:08
• @Shalini can you please copy and paste the INCAR into a code block rather than posting a screenshot? This way it's searchable and does not take so long to load on people's computers! Mar 15 at 22:50

How can I change this PBE to PW91 in INCAR to see the effect?

• According to the element order of your POSCAR, concatenate the different POTCARs in the GGA pseudopotentials library to generate the final POTCAR.

• Set the GGA tag in INCAR (All other tags in your screencast is OK to me.):

• PBE (default):

GGA=PE

• PW91

GGA=91

• PBEsol:

GGA=PS


More settings can refer to this link: https://www.vasp.at/wiki/index.php/GGA

Hope it helps.

• Thanks for reply . Could you please check attached INCAR and give feedback which I understood that just change the value in GGA tag according to different functionals . Mar 15 at 13:27
• @Shalini It's OK to me.
– Jack
Mar 15 at 14:17
• @Jack should the follow-up be a separate question? Anyway here is the link to the user's screenshot: i.stack.imgur.com/jkHhn.png, the answer will be deleted. Mar 15 at 15:20
• @NikeDattani It's not necessary. His question is not well organized.
– Jack
Mar 15 at 22:35
• @NikeDattani I have re-organized the question post.
– Jack
Mar 15 at 22:47