[Pw_forum] Occupation tag for isolated atom for a magnetic system

[Mudra Dave]

Dear QE users,
I have doubt regarding smearing and degauss value for magnetic system.
By refering old post of forum i got that degauss value is very important 
for a magnetic system and specially when calculation is performed for 
single atom.
1.In the 
example11 for single Al , occupation = "from input'' is used. I am 
unbale to understand how to decide occupancy values from electron 
configuration? is it related to degenrecy of particular orbit? 

2.I read in some post that,setting correct degauss is very important and to cheack convergence one may check smearing contribution in final energy 
zero. Is this one check parameter to check ground state?
3.For convergence issue i read if highest occupied and lowest unoccupied 
states if keep changing places,convergence can not be obtained, this can be solved by 
''adding few empty bands AND a small broading'' . Is this refering to 
occupation tag? 

Can we choose for occupation tag ,either of ''from input'' and ''smearing'' option, are they both equivalently apt? specially for transition metal 
magnetic system? And for single atom calculation? 

Any suggestion or help for getting clarity i highly appreciate.

Thanks in advance.
 
Mudra R Dave
Junior Research Fellow
Theoretical Condensed Matter Physics Group,
M S University of Baroda,
Vadodara,Gujarat.
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