Chalcopyrite semiconductors are ternary compounds with composition AIBIIIC2V, AIBIIIC2VI and AIIBIVC2V. Its structures can be considered derived from those of its binary analogs, zinc-blende, III-V and II-VI semiconductors compounds. In the chalcopyrites two different groups of cations are tetrahedally bonded to the anion, which lead to a reduction in symmetry, and typically smallest electronic band-gaps than those corresponding to their binary analogs. The interesting structural, electronic, and optical properties of these compounds provide a wide range of applications, for example in thin-film photovoltaic solar cells, optoelectronics, nonlinear optical devices, electro-optics, etc.
The AgGaSe2 chalcopyrite belongs to the AIBIIIC2VI family. Some experimental and few theoretical studies are available for this compound1-3. In this work we present an ab initio simulation study of the structural, elastic, and dynamical properties of AgGaSe2 chalcopyrite under high pressure. We perform the simulations using density functional theory4, DFT, with the pseudopotential method and the projector-augmented waves, PAW5. The generalized gradient approximation (GGA) was employed for the exchange-correlation energy. It is well known that first principle simulations provide accurate results with predictive character. We show the pressure evolution of the structural parameters and the equation of state, EOS, of this material. We provide interesting results concerning the elastic properties of this chalcopyrite under pressure, reporting fundamental properties related with its mechanical stability. We also study the vibrational properties under pressure of this system: Raman and infrared phonons, their pressure evolution, and Grüneisen parameters. Moreover, the dynamical stability of this chalcopyrite under pressure will be discussed.
References
[1] S. Klotz et al. “Anomalous pressure dependence of acoustic phonons of AgGaSe2 investigated by inelastic neutron scattering to 4.3 GPa”. Physica Status Solidi (b) 235, 331–336, (2003).
[2] N.S. Orlova, O.E. Andreeva, and I.V. Bodnar. “Pressure Effects on the Structural and Elastic Properties of AgGaS2–AgGaSe2Crystals: An X-ray Diffraction Study”. Inorganic Materials 37, 548–555, (2001).
[3] A. Chahed et al. “First-principles calculations of the structural, electronic and optical properties of AgGaS2 and AgGaSe2”. Physica B: Condensed Matter 367, 142–151, (2005).
[4] P. Hohenberg, and W. Kohn, Phys. Rev. 136, 3B, B864-871 (1964).
[5] P.E. Blöchl, Phys. Rev. B 50, 17953-17979, (1994).
*E-mail address: amunoz@ull.edu.es