QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: Dipankar Saha on November 19, 2015, 20:44

Title: GGA_PBE_sol
Post by: Dipankar Saha on November 19, 2015, 20:44

Hello,
Can we use the functional PBE_sol for the layered materials.... or,/ vdW hetero-structures ??

Thanks_
Dipankar

Title: Re: GGA_PBE_sol
Post by: Jess Wellendorff on November 23, 2015, 16:51

In order to use PBEsol instead of ordinary PBE, you simply specify "PBES" for the GGA xc functional:
exchange_correlation = GGA.PBES

Title: Re: GGA_PBE_sol
Post by: Dipankar Saha on November 23, 2015, 17:16

That's fine...  :) But, if we do that, we will not find any vdW correction..... That's why I asked....

Title: Re: GGA_PBE_sol
Post by: Anders Blom on November 23, 2015, 23:11

Well, there is a difference in asking "can we" (technical support) vs. "should we" (scientific advise) ;)

Title: Re: GGA_PBE_sol
Post by: Jess Wellendorff on November 24, 2015, 10:24

I suggest you go for the DFT-D3 method, which has official parameters for a number of GGA functionals, including PBEsol. If you look at Table 25 in the ATK reference manual (
http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.grimmedftd3.html (http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.grimmedftd3.html)), you will see the parameters to use. However, as stated in the text above the table, the VNL scripter supports setting the parameters for PBE, BLYP, and RPBE. So for PBEsol you need to set it manually:
1) Choose standard PBE and Grimme DFT-D3, and change the DFT-D3 parameters to match PBEsol and turn off the "three-body term" (see attached PNG).
2) Save the script and open it in an editor, and manually change from GGA.PBE to GGA.PBES.

Title: Re: GGA_PBE_sol
Post by: Dipankar Saha on November 25, 2015, 12:17

Ohhh...that's nice...!!! Thanks a lot Jess.... :)

Best_
Dipankar