[Pw_forum] Transmission calculation for simple metals

[Vladislav Borisov]

Dear all,

thank you very much for your kind help and the suggestions. As it occurs for the system 
I study, larger values of ewind, indeed, solve the problem with the transmission at some 
k-points, and now the convergence is achieved even for smaller epsproj < 1.e-7. 
I also agree that the optimal combination of parameters (ewind, epsproj) that provides 
a good convergence might be different in each case, as we noticed from the previous tests 
for other systems.

Regarding the question about the structure of cobalt:

> Finally, a word about the crystal structure. Are you sure that?s what you want? 
> The neighbors of the Co atoms seem to have different bond distances. Maybe you need 
> to choose another value for celldm(3)?

In fact, such tetragonally distorted fcc structure is exactly what we need in our study.

I have an additional question about the delgep parameter. According to its description, 
it is used for stability reasons when the eigenvalue problem is solved, and the default 
value is 5.e-10. It is also clear that the minimal possible value should be used, 
as long as the code doesn't crash. However, when I use the following setup for the 
calculation of cobalt

   ewind        = 400.d0,
   epsproj      = 1.d-10,
   delgep       = 5.d-10,
   nz1          = 22

the calculation ends with an error

     stopping ...

 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     Error in routine transmit (1029):
     problems with the linear system
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Getting back to values of the order of 1.e-7 solves the problem. Is it acceptable 
to use such relatively large values of delgep?


With kind regards,
Vladislav Borisov

Martin Luther University Halle-Wittenberg
Von-Seckendorff-Platz 1, Room 1.17
06120, Halle (Saale), Germany
Tel No: +49 (0) 345 55-25448
Fax No: +49 (0) 345 55-25446
Email: vladislav.borisov at physik.uni-halle.de