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edu no longer supports Internet Explorer. To browse Academia. edu and the wider internet faster and more securely, bruneval thesis take a few seconds to upgrade your browser, bruneval thesis. Log In with Facebook Log In with Google Sign Up with Apple. Remember me on this computer. Enter the email address you signed up with and we'll email you a reset link. Need an account? Click here to sign up. Download Free PDF. First-principle study of structural, electronic and elastic properties of bruneval thesis chalcogenides BeS, BeSe and BeTe Computational Materials Science, Saad Bin Omran.
Download PDF Download Full PDF Package This paper. A short summary of this paper. Download PDF. Download Full PDF Package. Translate PDF. Elghoula, K. Khirounia, and S. com Received March 18, Abstract—Cuprous oxide is selected as a promising material for photovoltaic applications. The effect of pressure on the structural and electronic properties of Cu2O is investigated.
Hexagonal and tetragonal phases are not completely indentified. We focus on the phase bruneval thesis of the cuprous oxide under hydrostatic pressure to tetragonal and hexagonal CdI2 structures. Variation of enthalpy with pressure is used to calculate the pressure of the phase transition. DOI: The taics are emerging [11, 12], bruneval thesis. A better understanding of cuprous oxide Cu2O was the first substance known to the atomic structure and electronic levels of cuprous behave as a semiconductor, together with selenium oxide may be useful for predicting and controlling the [1].
This oxide remains an in turn allow a better understanding of the growth attractive alternative material to silicon and other mechanism. Metal oxides present many polymorphs. It is nontoxic, resent an active field of investigation to discover a new its starting material which is copper is very abundant, stable phase or bruneval thesis an existent one [13].
These phase transitions have technique [3—5]. The first real solar cuprous oxide grows preferntially along the cell with Cu2O was fabricated in the late s. But at direction [17, 18]. The aim of orientation. We focus on the effect of 1 The article is published in the original. Table 1. The numerical mechanism in Cu2O. results given below correspond to zero temperature, bruneval thesis. Theoretical calculations are performed in the framework of the density functional theory DFT [20, 3.
It can be described as a cubic unit cell studies [23]. In the lattice, Ecut equal to 50 Hartree. The pseudopotentials are each copper atom coordinates with two oxygen atoms generated with the respective 3ds1 and 2s22p4 and each oxygen atom is surrounded by four copper atomic configurations bruneval thesis copper and oxygen. To obtain the equilibrium bulk Institute package [26], are used.
Figure 2 shows a parabolic approximation of Ceperly and Adler [27] by the dependence of the energy as a function of the volume. For the Brillouin zone sampling, ting a set of data points to the Murnaghan equation of state [31]. A fit of the resulting energy versus volume curve with the Murnaghan equation, shown in Fig.
Our calculated lattice parameters, bruneval thesis, the bulk moduli B0 and B' together with other theoretical and experimental values are listed in Table 2. timated by 2. Figures c and d are a zoom of the area showing cubic 䊉 and tetragonal 䊊 energies versus volume curves. It was confirmed in [16] Table bruneval thesis. the cubic and tetragonal structures.
Table 1 summarizes the atomic positions 2d, bruneval thesis. This observation is evident because the structural and space group for the three structures. In Fig, bruneval thesis. In order to look gents, bruneval thesis, and the phase transition pressure is given by the for the structural phase transition, the total energies slope of these lines, bruneval thesis.
are obtained as a function of the cell volume in the The pressure at which a phase transition occurs can three structures. The pressure of the phase transition is obtained and fitted by the Murnaghan equation of state are via the tangent construction using the energy versus shown in Fig, bruneval thesis.
Table 2. Calculated and experimental lattice parameters, bulk modulus, and pressure derivative of the bulk modulus for copper oxide in the cuprous, hexagonal, and tetragonal structures Structure a, Å c, bruneval thesis, Å B0, GPa B' Reference 4. This method is not very accurate. namics, at constant temperature and pressure, the This equation of state depends on a few parameters state of a system is determined by the Gibbs free and covers a wide range of pressures [37].
It depends on the nature of the interatomic interactions and thus where E and H bruneval thesis the internal energy and provides an insight into the nature of the solid state. At enthalpy, T and S are the temperature and entropy, bruneval thesis, and the same time, bruneval thesis, it determines the values of fundamental P and V are the pressure and volume.
We consider only thermodynamic parameters bruneval thesis. and at constant pressure. Variation of enthalpy versus pressure in the bruneval thesis, hexagonal, and tetragonal copper oxide with the a, bruneval thesis LDA and b, d PBE approximation. Figures c and d are a zoom of the area showing intersection lines of enthalpy versus pressure.
determined by the intersection of the two Gibbs free value of the transition pressure with the LDA energy isotherms Fig. At Pt, two phases have the and GGA. bruneval thesis enthalpy, bruneval thesis, and the transition pressure is then determined by equating the enthalpies of the two Figure 4 shows the band structure of copper oxide phases of cuprous oxide.
To see the possible phase in the three different structures at the experimental transitions, Figs. The maximum bruneval thesis the valence bands curves of the cubic, tetragonal, and hexagonal cuprous is set to the zero bruneval thesis in all plots.
For cuprous oxide, oxide as a function of pressure. Figures 3c and 3d are a it is observed that the direct band gap is about 0. tions [40, bruneval thesis, 41]. The underestimated band gap tal and theoretical reports bruneval thesis, 16]. In this study, the band gap is calculated with sures calculated with both LDA and GGA—PBE are the LDA. Hydrostatic damental gap of cuprous oxide is a direct one, with the pressure deforms the cubic structure to tetragonal at maximum of the valence band and the minimum of low pressure.
Our PBE result 4. Under pressure, the electronic structure Our calculation yields 8 GPa. The passage from the undergoes a drastic deformation. Cuprous oxide loses tetragonal to hexagonal structure is not known in the its semiconductor character and we observe an overlap literature, bruneval thesis. Our study gives a because tight bands occur as the effect of pressure. E, bruneval thesis, eV phs under pressure. The electronic structures of the cuprous oxide and two polymorphs are reproduced.
Tetragonal and hexagonal structures are conductive in our approximations, bruneval thesis. The value of the transition pressure of the cubic to the tetragonal and hexagonal phase is calculated in Eg very good agreement with results in the literature. Brattain, bruneval thesis, Rev. Leygraf, Atmospheric Corrosion Wiley, New York, 4 Rakhshani, A.
Varghese, Thin Solid Films Pollack and D. Trivich, J. Wijesundera, M. Hidaka, K. Koga, M. Sakai, bruneval thesis, and 0 EF W. Siripala, Thin Solid Films Slaby, bruneval thesis, Thin Solid Films 88, 33 Zhou and J.
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Apr 14, · Fabien Bruneval a); European Theoretical Spectroscopy Facility (ETSF), Laboratoire des Solides Irradiés, UMR , CNRS-CEA/DSM, École Polytechnique, F Palaiseau, France Francesco Sottile MotivationGWBSEMicro-macro Introduction to many-body Green’s functions Matteo Gatti European Theoretical Spectroscopy Facility (ETSF) NanoBio Spectroscopy Group - UPV San Sebastián - Spain Adragna PhD thesis and Adragna et al,PRB 68, (), Marini et al PRL 91, () Reining et al, PRL 88, (); Sottile PhD thesis and Sottile et al, PRL 91, () Bruneval PhD thesis and Bruneval, Sottile, Olevano, Del Sole, Reining, PRL ()
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