 EMTO: Exact MuffinTin Orbitals 
Definition:  An efficient
approach
to describe the
electronic wave
function of a
crystal structure in
terms of orbitals
localized at atomic
positions. 
Explanation:  The EMTO method is a
density functional
theory (→DFT)
method which is used
to solve
the one electron
Schrödinger
equations within
unit cells defined
around the lattice
sites. These unit
cells are chosen to
be the Wigner–Seitz
(WS) cells. The cell
for a given center
is constructed by
bisecting with a
plane each line
which
connects the
actual site with
another site, and
taking the closed
region around the
lattice site which
is bounded
by these planes. The
atomic potential
appearing in the
Schrödinger
equations is
approximated by the
optimized
overlapping
muffintin (MT)
spherical wells each
of which is centered
on a lattice site
and can spread
beyond the boundary
of the actual
WScell [1]. This is
in contrast to other
MT methods
where the potential
MTspheres are not
overlapped. The fact
that individual
MT
potentials are
allowed to overlap
makes the EMTO
method similar in
precision to
full potential
methods. The
combination of EMTO
method with the
coherent potential
approximation
(→CPA)
enables to
investigate
substitutionally
disordered alloys. 
References:  [1] L. Vitos. Computational Quantum Mechanics for Materials Engineers: The EMTO Method and Applications. Engineering Materials and Processes, Springer London (2007) 

