ISSN 10637761, Journal of Experimental and Theoretical Physics, 2014, Vol. 118, No. 2, pp. 235–241. © Pleiades Publishing, Inc., 2014.
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1. INTRODUCTION
Metal oxides are widely used in various applica
tions such as electronic components, building materi
als and refractories in drastic conditions of pressure
and/or temperature. Studies of metal oxides are thus
of great importance for obtaining a better understand
ing of corrosion of metals, heterogeneous catalysis, gas
sensors, and transparent conductive oxides. The
cuprous oxide (Cu
2
O) was the first substance known to
behave as a semiconductor, together with selenium
[1]. Most of the semiconductor theories were devel
oped using the data on Cu
2
O. This oxide remains an
attractive alternative material to silicon and other
semiconductors, being favored at present for many
applications due to its many advantages. It is nontoxic,
its starting material (which is copper) is very abundant,
and its production process is simple [2]. The most
important methods for the production of Cu
2
O are
thermal oxidation, electrodeposition, and sputtering
technique [3–5].
Cuprous oxide is a potential material for fabrica
tion of lowcost solar cells [6, 7]. The first real solar
cell with Cu
2
O was fabricated in the late 1920s. But at
that time, and until the first space explorations, the
energy production from the sun by photovoltaic effect
was just a curiosity. Highefficiency Cu
2
O–based solar
cells require a good understanding of the crystallinity
of this oxide and a judicious choice of the structural
orientation. Cu
2
O is a ptype semiconductor; it crys
1
The article is published in the original.
tallizes in the cubic structure (Pn–3m) and has a direct
band gap of about 2 eV [8], which is suitable for pho
tovoltaic conversion [9, 10].
Cuprous oxide has been the subject of numerous
theoretical and experimental studies, but still its elec
tronic and atomic structures continue to puzzle the
researchers. New applications of Cu
2
O in nanoelec
tronics, spintronics, superconductivity, and photovol
taics are emerging [11, 12]. A better understanding of
the atomic structure and electronic levels of cuprous
oxide may be useful for predicting and controlling the
phase transition under hydrostatic pressure, which will
in turn allow a better understanding of the growth
mechanism. Metal oxides present many polymorphs.
The stability and mechanism of phase transitions rep
resent an active field of investigation to discover a new
stable phase or improve an existent one [13]. In ambi
ent conditions, Cu
2
O stabilizes in a simple cubic Bra
vais lattice, with the space group Pn–3m(223) [14].
Under high pressure, the cubic phase has a number of
lowpressure phases. These phase transitions have
been studied both theoretically and experimentally
[15, 16]. Experimental studies have shown that
cuprous oxide grows preferntially along the (111)
direction [17, 18]. Atomic stacking along this direc
tion coincides well with the hexagonal structure [19].
The present work is focused on clarifying some fun
damental aspects of Cu
2
O that can be important for
both device fabrication and a better understanding of
the physical phenomena observed in Cu
2
O. The aim of
this work is to characterize hexagonal and tetragonal
structure of cuprous oxide. We focus on the effect of
pressure in the structural and electronic properties of
FirstPrinciple Study of the Structural, Electronic,
and Thermodynamic Properties of Cuprous Oxide under Pressure
1
M. Zemzemi
a,
*, N. Elghoul
a
, K. Khirouni
a
, and S. Alaya
a,b
a
Laboratoire de Physique des Matériaux et des Nanomatériaux appliquée á l’Environnement, Université de Gabés,
Faculté des Sciences de Gabés, Cité Erriadh Zrig Gabés, 6072 Tunisie
b
King Faisal University, College of Science, Physics Department, Hofuf, 31982 Saudi Arabia
*email: mzemzemi@gmail.com
Received March 18, 2013
Abstract—Cuprous oxide is selected as a promising material for photovoltaic applications. Density func
tional theory is used to study the structural, electronic, and thermodynamic properties of cuprous oxide by
using the local density approximation and generalizedgradient approximation. The effect of pressure on the
structural and electronic properties of Cu
2
O is investigated. This study confirms and characterizes the exist
ence of new phases. Hexagonal and tetragonal phases are not completely indentified. We focus on the phase
transition of the cuprous oxide under hydrostatic pressure to tetragonal and hexagonal (CdI
2
) structures.
Variation of enthalpy with pressure is used to calculate the pressure of the phase transition.
DOI: 10.1134/S1063776114020228
SOLIDS
AND LIQUIDS