C-parameter in mbj calculation (from wien mailing list)

david yang Fri, 19 Sep 2014 03:43:02 -0700

 

Dear Prof. Blaha and WiEN2K users,

I am trying to correct bandgap of a semiconductor by using mbj method.  I
want to know where ( in which file) the c-default c-parameter value is
printed. Also How can I tune the c-parameter for bandgap adjustment.  Your
Help in this regard will be highly appreciate.



Thanks and Regards
David Yang
NUS Singapore.

Answer of Prof F.Tran

tran Fri, 19 Sep 2014 04:20:45 -0700

 

The value of c is printed in case.scf. This is the 2nd value at the line which starts with :GRR28. You can choose the value of c by specifying A (=alpha), B (=beta) and e in case.in0abp. You have explanations in Sec. 4.5.9 of the user's guide. Usually, an increase of c leads to an increase of the band gap.

F.Tran

Answer of Prof P.Blaha

Peter Blaha Fri, 19 Sep 2014 04:29:01 -0700

 

In addition, there is a file case.grr (which is generated if case.in0_grr is present) and it contains the average of grad|rho|/rho, which is the value which besides the functional form (see previous mail) determines "c". For instance for a surface it is recommended to calculate first the "bulk" material, and then transfer case.grr to the surface (and delete case.in0_grr there). In this way, the surface will use the same "c" value as the bulk.

Reference: https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg11164.html