INTRODUCTION
Transparent semiconducting oxides (TCOs), such as ZnO, SnO, In
2
O
3
, CdO, SnCd
2
O
4
(CTO) and SnZn
2
O
4
(ZTO), demonstrate great applications in various areas including smart windows, flat-panel displays, thin-film
photovoltaic, transparent electrodes for solar cell and polymer-based electronics due to their unique electrical and
optical properties. Two of the best TCO materials, indium-tin-oxides and cadmium-tin-oxides, contain ether expensive
or toxic elements and may not be desirable for future large-area applications. For Zinc stannate, SnZn
2
O
4
(ZTO), is n-
typed semiconducting material with wide band gap of 3.6 eV (T. Minami
et al
., 1994) an inexpensive optically
transparent, electrically conducting, and nontoxic oxide, SnZn
2
O
4
is known to have high chemical sensitivity, high
electrical conductivity, high electron mobility, and low visible absorption. SnZn
2
O
4
is ternary compound that has a
general chemical formula (A)[B
2
]O
4
, where parentheses, (…) represents the tetrahedral sites […] represents the
octahedral sites, and usually exist in either the cubic spinel structure. Many experimental and theoretical studies have
been carried out to understanding the structural, electrical, and optical properties of this ternary compounds. For
example, it is known that CdIn
2
O
4
is possibly more stable in the normal spinel structure,
whereas SnZn
2
O
4
and
SnCd
2
O
4
are more stable in the inverse spinel structure. The inverse spinel can particularly be described by the
formula (B)[AB]O
4
. Using first-principle band structure and total energy methods, we have studied the structural,
electronic properties of SnZn
2
O
4
. In particular, we have investigated the relationship that of the different crystal
structures, i.e. in between normal and inverse spinel structures and the electronic dispersion relation including density
of state in this ternary compound. The finding will help us in future studies and design of high-performance TCOs.
CRYSTAL STRUCTURES
The normal spinel structures are present by AB
2
O
4
with space group; Fd3m (O
7
h
), in which one-eighth of the
tetrahedral void in a face-center-cubic (fcc) close-packed oxygen sublattices are occupied by A atoms [see Fig.1(a)]
and one-half of the octahedral voids are occupied by B atoms [see Fig.1(b)]. There exist also an “inverse” spinel
structure, where the tetrahedral voids are occupied by B atoms and the octahedral voids are occupied randomly by an
equal number of A and B atoms, where A is Sn
4+
ions and B is Zn
2+
ions. The normal spinel crystal structure is
determined by two parameters: the lattice constant
a
and the anion displacement
u
. The bond length between the A
atom at the center of a AO
4
tetrahedron and its four nearest-neighbor oxygen atoms is given by
R
tetra
=
(
u
– 0.25)
a
, (1)
whereas the bond length between the B atom at the corner of octahedron and their six nearest oxygen atoms is
R
octa
=
a
. (2)
For the inverse spinel structure, our modeled results are in good agreement with other models, where using a
small special quasi random structure (SQS), which has same lattice vectors as normal spinel (Su-Huai Wei
et al
.,
2001).
