[Pw_forum] Can one set the c-parameter in the TB09 functional?

[Florian Fuchs]

Dear experts,


I want to use the meta-GGA functional introduced by Tran and Blaha  
(Phys. Rev. Lett. 102, 2009) and implemented within Quantum Espresso  
by Germaneau et al. (Computer Physics Communications 184, 2013).  
Looking at the Modules/funct.f90 file, I found that the functional is  
available and one can select it by setting input_dft to TB09. As you  
may know, this functional includes a parameter, which has been  
introduced by Tran and Blaha to improve the calculated band gaps of a  
given material. The parameter can be calculated or it can be used as a  
fitting parameter.

I would like to set this parameter manually to adjust the band gap to  
some reference data. Is it possible to set this parameter in Quantum  
Espresso? How can I do this without changing the source code?

Thank you in advance.


Kind regards,
Florian Fuchs