Dear all,

We have a fews questions/doubts concerning the ns occupation matrix for LDA+U 
calculations (starting_ns_eigenvalue(m,ispin,I)). Following the idea presented 
in example 25 of quantum espresso, we are trying to fix the initial occupation 
of the "d" orbital of Ni in a monolayer of NiO in an anti-ferromagnetic state. 
The questions we have are:

1) Are each of the diagonal elements of the occupation matrix associated with 
the d orbitals? Something like, 
(1,1) -> dz2, (2,2) -> dzx, (3,3) -> dzy, (4,4) -> d(x2-y2) and? 
(5,5) -> dxy?? ?
2) If there is this correspondence, is it possible to specify an initial 
occupation of each of the orbitals after the initial guess is evaluated in the 
first iteration? For example, in the attached input, how could we specify that 
only the dz2, dxz and dyz orbitals are initially completely occupied with 2 
electrons? In other words, how can we change the "spin down occupation matrix" 
of the Ni atom from 
0.6 0.0 0.0 0.0 0.0???? ?? ? ? 1.0 0.0 0.0 0.0 0.0
0.0 0.6 0.0 0.0 0.0???? ?? ? ? 0.0 1.0 0.0 0.0 0.0
0.0 0.0 0.6 0.0 0.0???? ->??? 0.0 0.0 1.0 0.0 0.0
0.0 0.0 0.0 0.6 0.0???? ?? ??? 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.6???? ?? ??? 0.0 0.0 0.0 0.0 0.0
??

Thanks very much for your time,
With best regards,

Luca Sementa, F?bio Negreiros
Postdoc students,
IPCF - CNR - Pisa, Italy
 

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