[Pw_forum] degauss

[Giuseppe Mattioli]

Dear Raheleh

In the case of degauss, you should use the smallest value at which your 
calculation does not struggle to converge. Try, e.g., 0.01 Ry. Look in the 
output at the smearing contribution to total energy 

smearing contrib. (-TS)   =       0.00081361 Ry

and make some tests to ensure that your total energy values are quite 
unaffected by different smearing values.
If your system is an insulator, you should face no particular problems.

In the case of mixing beta, you can start with a quite high value, e.g., 0.5, 
in a davidson diagonalization scheme. If your scf calculation does not 
converge you could try to reduce the mixing value down to 0.1 or 0.05 (this 
will slow your calculation...) or to use the robust cg diagonalization scheme 
(this will slow very much your calculation...).

Hope this helps

Giuseppe

On Saturday 08 May 2010 10:04:55 raheleh vaziri wrote:
> Dear All,
>
>
>  I don't know that my molecule is metal, insulator or semiconductor , thus,
> what is suitable value for degauss and mixing_beta?
>
> thank you for any help
>
> Raheleh Vaziri.



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   Giuseppe Mattioli                            
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