[Pw_forum] why are there two Fermi energies?

[Eduardo Ariel Menendez Proupin]

Hi,
Why are there two Fermi energies in certain spin-polarized calculations ?

input             starting_magnetization(1) = 0.0,
                    starting_magnetization(2) = 0.5,
output      the Fermi energy is     6.1598 ev
               !    total energy              =    -502.92538790 Ry

input           tot_magnetization = 1
output     the spin up/dw Fermi energies are     6.3821    6.1598 ev
              !    total energy              =    -502.92538790 Ry

What is the meaning of the spin up Fermi level in the second case?

This numbers are for a 64 atoms Si unit cell with one Si replaced by Al, and
only one k-point, but the same happens with more k-points. I also used Fermi
smearing with a very low smearing.
 There is a difference if I set the starting magnetization or the total
magnetization, with pw.x version 4.2.1. However, despite reporting different
Fermi levels, the total energy and magnetization are equal. Also are equal
KS energies, at least around the Fermi levels.

Thanks,

Eduardo Menendez
Departamento de Fisica
Facultad de Ciencias
Universidad de Chile
Phone: (56)(2)9787439
URL: http://fisica.ciencias.uchile.cl/~emenendez
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