Unless otherwise specified, all PWscf input and output quantities are in atomic "Rydberg" units, i.e. energies in Ry, lengths in Bohr radii, etc.. Note that CP uses instead atomic "Hartree" units: energies in Ha, lengths in Bohr radii.
In most cases: your input data is bad, or else your system is metallic
and you are treating it as an insulator. If this is not the case:
reduce mixing_beta to
0.3 ÷ 0.1 or smaller,
try the mixing_mode value that is more
appropriate for your problem.
The total magnetization is the integral of the magnetization in the cell:
There is no 'right' way of defining the local magnetic moment around an atom in a multi-atom system. However an approximate way to define it is via the projected density of states on the atomic orbitals (code projwfc.x, see example08 for its use as a postprocessing tool). This code generate many files with the density of states projected on each atomic wavefunction of each atom and a BIG amount of data on the standard output, the last few lines of which contain the decomposition of Lowdin charges on angular momentum and spin component of each atom.
See input data documentation for projwfc.x.
"Lowdin charges (as well as other conventional atomic charges) do not satisfy any sum rule. You can easily convince yourself that this is the case because the atomic orbitals that are used to calculate them are arbitrary to some extent. If you like, you can think that the missing charge is "delocalized" or "bonding" charge, but this would be another way of naming the conventional (to some extent) character of Löwdin charge." (Stefano Baroni, Sept. 2008).
See also the definition of "spilling parameter": Sanchez-Portal et al., Sol. State Commun. 95, 685 (1995). The spilling parameter measures the ability of the basis provided by the pseudo-atomic wfc to represent the PW eigenstates, by measuring how much of the subspace of the Hamiltonian eigenstates falls outside the subspace spanned by the atomic basis.
It is printed in the output. If not, the information on Gaussian smearing, needed to calculate a sensible Fermi energy, was not provided in input. In this case, pw.x prints instead the highest occupied and lowest unoccupied levels. If not, the number of bands to be calculated was not provided in input and pw.x calculates occupied bands only.
The reference level is an ill-defined quantity in calculations in solids with periodic boundary conditions. Absolute values of Kohn-Sham eigenvalues are meaningless.
"The value of the Fermi energy (as well as of any energy, for that matter) depends of the reference level. What you are referring to is probably the "Fermi energy referred to the vacuum level" (i.e. the work function). In order to obtain that, you need to know what the vacuum level is, which cannot be said from a bulk calculation only" (Stefano Baroni, Sept. 2008).
More often than not, this charges are a slightly too hard to be expanded very accurately in PWs, hence some aliasing error will be introduced. Especially if the unit cell is big and mostly empty, some local low negative charge density will be produced.
''This is NOT harmful at all, the negative charge density is handled properly by the code and will disappear during the self-consistent cycles'', but if it is very high (let's say more than 0.001*number of electrons) it may be a symptom that your charge density cutoff is too low. (L. Paulatto - November 2008)
Work function = (average potential in the vacuum) - (Fermi Energy). The former is estimated in a supercell with the slab geometry, by looking at the average of the electrostatic potential (typically without the XC part). See the example in examples/WorkFct_example.