[Wien] fermi wave vector Kf

[Gavin Abo]

Is Kf the radius to the fermi surface [1]?

If so, maybe you can extract it from a fermi surface calculation [2] using:

a) XCrySDen [3]

or

b) FSGEN [4]

I have also seen the PW91 GGA equation [5]:

kF = (3*pi^2*n)^(1/3)

In a terminal, if you do:

cd $WIENROOT/SRC_lapw0

grep TKF *

In the output, you should see for example:

vxi35.f: TKF = 2.D0*(3.D0*PI2*D)**THRD

 From above, it looks like TKF = 2*kF, where D = n.

Though, it is noted that the vxi35.f code might be for another 
functional other than PW91 GGA. So you would have to test and determine 
yourself which functional(s) and/or nuances that line of code is for.  
Also, I'm not seeing TKF written to any output file.  So you would 
likely have to add your own code to output the TKF values, such as with 
a WRITE statement [6].

Hope that helps and good luck.

[1] 
https://www.fhi-berlin.mpg.de/~wolf/femtoweb/teaching/WS0506-wolf-festk/WS0506/material/free_electron3_4.pdf
[2] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg02526.html
[3] http://www.xcrysden.org/doc/fermi.html
[4] Section "8.7 FSGEN (Fermi-surface generation)" on page 159 in the 
WIEN2k 17.1 usersguide ( 
http://susi.theochem.tuwien.ac.at/reg_user/textbooks/usersguide.pdf )
[5] Equation 29 in chapter "Derivation of a Generalized Gradient 
Approximation: The PW91 Density Functional" of the book titled 
"Electronic Density Functional Theory:Recent Progress and New 
Directions" ( http://www.springer.com/us/book/9780306458347 )
[6] Intel Fortran Compiler 17.0 Developer Guide and Reference ( 
https://software.intel.com/en-us/node/680026 )

On 10/22/2017 1:00 AM, Amir Zayyani wrote:
> Dear Prof. P. Blaha
>
> I want to know where the exact amount of fermi wave vector Kf is and in which file i can find it
>
>
> Best Regards
>
> Zayyani