 DOS: Density Of States 
Definition:  A DOS plot depicts
the number of
available electronic
states for each
energy level of a
crystalline system.
Important
information, such as
the
number of occupied
states at the Fermi
level as well as the
width of the band
gap for
insulators or
semiconductors, can
be read easily and
directly from the
DOS
plot. 
Explanation:  A central concept in
computational
materials science is
the electronic band
structure, which
represents the
quantumchemically
computed energy
eigen values of a
crystal. It is the
solid state analogue
of a
molecularorbital
diagram. The latter
illustrates the
discrete states of
the molecular
orbitals and their
energies. Each
atomic orbital of
the participating
atoms results in a
molecular orbital.
For crystals, the
scenario is similar:
each atomic orbital
contributes to the
entire(delocalized)
crystal orbitals.
Due to a large
number of atoms and
orbitals, the
discrete states
combine
into bands. The
figure below (left)
shows the resulting
band structure for
facecentred cubic
(→fcc)
Fe as an
example; it is built
from an infinite
number of atoms, and
the
different bands
represents the
different orbitals.
For clarity, only
the band
structure is plotted
and
between chosen k
points; however, a
complete
figure requires the
structure at any
k.
For most
applications,
it is
sufficient to know
the number of states
as a function of
energy. Such a plot
is known as DOS,
where easier
analysis is
possible. In order
to
retain the picture
from the band
structure, chemists
switch the x
and y
axes of the DOS and
plot the energy as a
function of the
number of states. 
Picture / Figure / Diagram: 

Band structure (left) and DOS (right) plots for austenitic iron (fcc Fe).


SFBLink:  The analyses of DOS plots are applied by subproject A1 to different structures of SFB materials in order to understand their chemistry and stability. 
References:  R. Dronskowski, Computational Chemistry of Solid State Materials, WileyVCH, Weinheim, 2005. 

