Numerical MHD Simulations of Solar Magnetoconvection and Oscillations in Inclined Magnetic Field Regions

The sunspot penumbra is a transition zone between the strong vertical magnetic field area (sunspot umbra) and the quiet Sun. The penumbra has a fine filamentary structure that is characterized by magnetic field lines inclined toward the surface. Numerical simulations of solar convection in inclined magnetic field regions have provided an explanation of the filamentary structure and the Evershed outflow in the penumbra. In this paper, we use radiative MHD simulations to investigate the influence of the magnetic field inclination on the power spectrum of vertical velocity oscillations. The results reveal a strong shift of the resonance mode peaks to higher frequencies in the case of a highly inclined magnetic field. The frequency shift for the inclined field is significantly greater than that in vertical field regions of similar strength. This is consistent with the behavior of fast MHD waves.Comment: 9 pages, 6 figures, Solar Physics (in press

Imaging the Solar Tachocline by Time-Distance Helioseismology

The solar tachocline at the bottom of the convection zone is an important region for the dynamics of the Sun and the solar dynamo. In this region, the sound speed inferred by global helioseismology exhibits a bump of approximately 0.4% relative to the standard solar model. Global helioseismology does not provide any information on possible latitudinal variations or asymmetries between the Northern and Southern hemisphere. Here, we develop a time-distance helioseismology technique, including surface- and deep-focusing measurement schemes and a combination of both, for two-dimensional tomographic imaging of the solar tachocline that infers radial and latitudinal variations in the sound speed. We test the technique using artificial solar oscillation data obtained from numerical simulations. The technique successfully recovers major features of the simplified tachocline models. The technique is then applied to SOHO/MDI medium-l data and provides for the first time a full two-dimensional sound-speed perturbation image of the solar tachocline. The one-dimensional radial profile obtained by latitudinal averaging of the image is in good agreement with the previous global helioseismology result. It is found that the amplitude of the sound-speed perturbation at the tachocline varies with latitude, but it is not clear whether this is in part or fully an effect of instrumental distortion. Our initial results demonstrate that time-distance helioseismology can be used to probe the deep interior structure of the Sun, including the solar tachocline.Comment: accepted for publication by Ap

High-pressure effects on the optical-absorption edge of CdIn2S4, MgIn2S4, and MnIn2S4 thiospinels

The effect of pressure on the optical-absorption edge of CdIn2S4, MgIn2S4, and MnIn2S4 thiospinels at room temperature is investigated up to 20 GPa. The pressure dependence of their band-gaps has been analyzed using the Urbach rule. We have found that, within the pressure-range of stability of the low-pressure spinel phase, the band-gap of CdIn2S4 and MgIn2S4 exhibits a linear blue-shift with pressure, whereas the band-gap of MnIn2S4 exhibits a pronounced non-linear shift. In addition, an abrupt decrease of the band-gap energies occurs in the three compounds at pressures of 10 GPa, 8.5 GPa, and 7.2 GPa, respectively. Beyond these pressures, the optical-absorption edge red-shifts upon compression for the three studied thiospinels. All these results are discussed in terms of the electronic structure of each compound and their reported structural changes.Comment: 18 pages, 3 figure

Thermally-activated cation ordering in ZnGa2Se4 single crystals studied by Raman scattering, optical absorption, and ab initio calculations

Order-disorder phase transitions induced by thermal annealing have been studied in the ordered-vacancy compound ZnGa2Se4 by means of Raman scattering and optical absorption measurements. The partially disordered as-grown sample with tetragonal defect stannite (DS) structure and I (4) over bar 2m space group has been subjected to controlled heating and cooling cycles. In situ Raman scattering measurements carried out during the whole annealing cycle show that annealing the sample to 400 degrees C results in a cation ordering in the sample, leading to the crystallization of the ordered tetragonal defect chalcopyrite (DC) structure with I (4) over bar space group. On decreasing temperature the ordered cation scheme of the DC phase can be retained at ambient conditions. The symmetry of the Raman-active modes in both DS and DC phases is discussed and the similarities and differences between the Raman spectra of the two phases emphasized. The ordered structure of annealed samples is confirmed by optical absorption measurements and ab initio calculations, that show that the direct bandgap of DC-ZnGa2Se4 is larger than that of DS-ZnGa2Se4.This study was supported by the Spanish government MEC under grants MAT2010-21270-C04-01/03/04 and MAT2010-19837-C06-06, by MALTA Consolider Ingenio 2010 project (CSD2007-00045), and by the Vicerrectorado de Investigacion y Desarrollo of the Universitat Politecnica de Valencia (UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11). EP-G, AM, and PR-H acknowledge computing time provided by Red Espanola de Supercomputacion (RES) and MALTA-Cluster. Finally, the authors would also like to acknowledge M C Moron for stimulating discussions and revision of the present manuscript.Vilaplana Cerda, RI.; Gomis Hilario, O.; Pérez-González, E.; Ortiz, HM.; Manjón Herrera, FJ.; Rodríguez-Hernández, P.; Muñoz, A.... (2013). Thermally-activated cation ordering in ZnGa2Se4 single crystals studied by Raman scattering, optical absorption, and ab initio calculations. Journal of Physics: Condensed Matter. 25(16):165802-1-165802-11. https://doi.org/10.1088/0953-8984/25/16/165802S165802-1165802-112516Bernard, J. E., & Zunger, A. (1988). Ordered-vacancy-compound semiconductors: PseudocubicCdIn2Se4. Physical Review B, 37(12), 6835-6856. doi:10.1103/physrevb.37.6835Jiang, X., & Lambrecht, W. R. L. (2004). Electronic band structure of ordered vacancy defect chalcopyrite compounds with formulaII−III2−VI4. Physical Review B, 69(3). doi:10.1103/physrevb.69.035201Yahia, I. S., Fadel, M., Sakr, G. B., & Shenouda, S. S. (2010). Memory switching of ZnGa2Se4 thin films as a new material for phase change memories (PCMs). Journal of Alloys and Compounds, 507(2), 551-556. doi:10.1016/j.jallcom.2010.08.021Yahia, I. S., Fadel, M., Sakr, G. B., Yakuphanoglu, F., Shenouda, S. S., & Farooq, W. A. (2011). Analysis of current–voltage characteristics of Al/p-ZnGa2Se4/n-Si nanocrystalline heterojunction diode. Journal of Alloys and Compounds, 509(12), 4414-4419. doi:10.1016/j.jallcom.2011.01.068Hahn, H., Frank, G., Klingler, W., St�rger, A. D., & St�rger, G. (1955). Untersuchungen �ber tern�re Chalkogenide. VI. �ber Tern�re Chalkogenide des Aluminiums, Galliums und Indiums mit Zink, Cadmium und Quecksilber. Zeitschrift f�r anorganische und allgemeine Chemie, 279(5-6), 241-270. doi:10.1002/zaac.19552790502Errandonea, D., Kumar, R. S., Manjón, F. J., Ursaki, V. V., & Tiginyanu, I. M. (2008). High-pressure x-ray diffraction study on the structure and phase transitions of the defect-stannite ZnGa2Se4 and defect-chalcopyrite CdGa2S4. Journal of Applied Physics, 104(6), 063524. doi:10.1063/1.2981089Morón, M. C., & Hull, S. (2003). Order-disorder phase transition inZn1−xMnxGa2Se4: Long-range order parameter versusx. Physical Review B, 67(12). doi:10.1103/physrevb.67.125208Morón, M. C., & Hull, S. (2005). Effect of magnetic dilution in Zn1−xMnxGa2Se4 (0<x<0.5). Journal of Applied Physics, 98(1), 013904. doi:10.1063/1.1944220Morón, M. C., & Hull, S. (2007). The influence of magnetic dilution in the Zn1−xMnxGa2Se4 series with 0.5<x⩽1. Journal of Applied Physics, 102(3), 033919. doi:10.1063/1.2767273Antonioli, G., Lottici, P. P., & Razzetti, C. (1989). The structure of the defect chalcopyrite ZnGa2Se4 studied by EXAFS. physica status solidi (b), 152(1), 39-49. doi:10.1002/pssb.2221520104Haeuseler, H. (1978). FIR- und Ramanspektren von ternären Chalkogeniden des Galliums und Indiums mit Zink, Cadmium und Quecksilber. Journal of Solid State Chemistry, 26(4), 367-376. doi:10.1016/0022-4596(78)90171-8Eifler, A., Krauss, G., Riede, V., Krämer, V., & Grill, W. (2005). Optical phonon modes and structure of ZnGa2Se4 and ZnGa2S4. Journal of Physics and Chemistry of Solids, 66(11), 2052-2057. doi:10.1016/j.jpcs.2005.09.049Lottici, P. P., & Razzetti, C. (1983). A comparison of the raman spectra of ZnGa2Se4 and other gallium defect chalcopyrites. Solid State Communications, 46(9), 681-684. doi:10.1016/0038-1098(83)90506-9Razzetti, C., Lottici, P. P., & Antonioli, G. (1987). Structure and lattice dynamics of nonmagnetic defective AIIBIII2XIV4 compounds and alloys. Progress in Crystal Growth and Characterization, 15(1), 43-73. doi:10.1016/0146-3535(87)90009-8Attolini, G., Bini, S., Lottici, P. P., & Razzetti, C. (1992). Effects of Group III Cation Substitution in the Raman Spectra of Some Defective Chalcopyrites. Crystal Research and Technology, 27(5), 685-690. doi:10.1002/crat.2170270519Takahashi, Y., Namatsu, H., Machida, K., & Minegishi, K. (1993). Measurements of Diffusion Coefficiens of Water in Electron Cryclotron Resonance Plasma SiO2. Japanese Journal of Applied Physics, 32(Part 2, No. 3B), L431-L433. doi:10.1143/jjap.32.l431Ursaki, V. V., Burlakov, I. I., Tiginyanu, I. M., Raptis, Y. S., Anastassakis, E., & Anedda, A. (1999). Phase transitions in defect chalcopyrite compounds under hydrostatic pressure. Physical Review B, 59(1), 257-268. doi:10.1103/physrevb.59.257Allakhverdiev, K., Gashimzade, F., Kerimova, T., Mitani, T., Naitou, T., Matsuishi, K., & Onari, S. (2003). Raman scattering under pressure in ZnGa2Se4. Journal of Physics and Chemistry of Solids, 64(9-10), 1597-1601. doi:10.1016/s0022-3697(03)00077-5Alonso-Gutiérrez, P., Sanjuán, M. L., & Morón, M. C. (2009). Thermally activated cation ordering in Zn0.5Mn0.5Ga2Se4single crystals studied by Raman scattering. physica status solidi (c), 6(5), 1182-1186. doi:10.1002/pssc.200881218Caldera, D., Morocoima, M., Quintero, M., Rincon, C., Casanova, R., & Grima, P. (2011). On the crystal structure of the defective ternary compound. Solid State Communications, 151(3), 212-215. doi:10.1016/j.ssc.2010.11.031Gomis, O., Vilaplana, R., Manjón, F. J., Pérez-González, E., López-Solano, J., Rodríguez-Hernández, P., … Ursaki, V. V. (2012). High-pressure optical and vibrational properties of CdGa2Se4: Order-disorder processes in adamantine compounds. Journal of Applied Physics, 111(1), 013518. doi:10.1063/1.3675162Eifler, A., Hecht, J.-D., Lippold, G., Riede, V., Grill, W., Krauß, G., & Krämer, V. (1999). Combined infrared and Raman study of the optical phonons of defect chalcopyrite single crystals. Physica B: Condensed Matter, 263-264, 806-808. doi:10.1016/s0921-4526(98)01292-7Sanjuán, M. L., & Morón, M. C. (2002). Raman study of Zn1−xMnxGa2Se4 diluted magnetic semiconductors: disorder and resonance effects. Physica B: Condensed Matter, 316-317, 565-567. doi:10.1016/s0921-4526(02)00574-4Letoullec, R., Pinceaux, J. P., & Loubeyre, P. (1988). The membrane diamond anvil cell: A new device for generating continuous pressure and temperature variations. High Pressure Research, 1(1), 77-90. doi:10.1080/08957958808202482Perdew, J. P., Burke, K., & Ernzerhof, M. (1997). Generalized Gradient Approximation Made Simple [Phys. Rev. Lett. 77, 3865 (1996)]. Physical Review Letters, 78(7), 1396-1396. doi:10.1103/physrevlett.78.1396Manjón, F. J., Gomis, O., Rodríguez-Hernández, P., Pérez-González, E., Muñoz, A., Errandonea, D., … Ursaki, V. V. (2010). Nonlinear pressure dependence of the direct band gap in adamantine ordered-vacancy compounds. Physical Review B, 81(19). doi:10.1103/physrevb.81.195201Santamaría-Pérez, D., Amboage, M., Manjón, F. J., Errandonea, D., Muñoz, A., Rodríguez-Hernández, P., … Tiginyanu, I. M. (2012). Crystal Chemistry of CdIn2S4, MgIn2S4, and MnIn2S4 Thiospinels under High Pressure. The Journal of Physical Chemistry C, 116(26), 14078-14087. doi:10.1021/jp303164kBaroni, S., de Gironcoli, S., Dal Corso, A., & Giannozzi, P. (2001). Phonons and related crystal properties from density-functional perturbation theory. Reviews of Modern Physics, 73(2), 515-562. doi:10.1103/revmodphys.73.515Giannozzi, P., Baroni, S., Bonini, N., Calandra, M., Car, R., Cavazzoni, C., … Wentzcovitch, R. M. (2009). QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials. Journal of Physics: Condensed Matter, 21(39), 395502. doi:10.1088/0953-8984/21/39/395502Kroumova, E., Aroyo, M. I., Perez-Mato, J. M., Kirov, A., Capillas, C., Ivantchev, S., & Wondratschek, H. (2003). Bilbao Crystallographic Server : Useful Databases and Tools for Phase-Transition Studies. Phase Transitions, 76(1-2), 155-170. doi:10.1080/0141159031000076110Loudon, R. (1964). The Raman effect in crystals. Advances in Physics, 13(52), 423-482. doi:10.1080/00018736400101051Alonso-Gutiérrez, P., & Sanjuán, M. L. (2008). Ordinary and extraordinary phonons and photons: Raman study of anisotropy effects in the polar modes ofMnGa2Se4. Physical Review B, 78(4). doi:10.1103/physrevb.78.045212Manjón, F. J., Marí, B., Serrano, J., & Romero, A. H. (2005). Silent Raman modes in zinc oxide and related nitrides. Journal of Applied Physics, 97(5), 053516. doi:10.1063/1.1856222Garbato, L., Ledda, F., & Rucci, A. (1987). Structural distortions and polymorphic behaviour in ABC2 and AB2C4 tetrahedral compounds. Progress in Crystal Growth and Characterization, 15(1), 1-41. doi:10.1016/0146-3535(87)90008-6Grzechnik, A., Ursaki, V. V., Syassen, K., Loa, I., Tiginyanu, I. M., & Hanfland, M. (2001). Pressure-Induced Phase Transitions in Cadmium Thiogallate CdGa2Se4. Journal of Solid State Chemistry, 160(1), 205-211. doi:10.1006/jssc.2001.9224Marquina, J., Power, C., Grima, P., Morocoima, M., Quintero, M., Couzinet, B., … González, J. (2006). Crystallographic properties of the MnGa2Se4 compound under high pressure. Journal of Applied Physics, 100(9), 093513. doi:10.1063/1.2358826Meenakshi, S., Vijayakumar, V., Eifler, A., & Hochheimer, H. D. (2010). Pressure-induced phase transition in defect Chalcopyrites HgAl2Se4 and CdAl2S4. Journal of Physics and Chemistry of Solids, 71(5), 832-835. doi:10.1016/j.jpcs.2010.02.007Gomis, O., Vilaplana, R., Manjón, F. J., Santamaría-Pérez, D., Errandonea, D., Pérez-González, E., … Ursaki, V. V. (2013). High-pressure study of the structural and elastic properties of defect-chalcopyrite HgGa2Se4. Journal of Applied Physics, 113(7), 073510. doi:10.1063/1.4792495Lowe-Ma, C. K., & Vanderah, T. A. (1991). Structure of ZnGa2S4, a defect sphalerite derivative. Acta Crystallographica Section C Crystal Structure Communications, 47(5), 919-924. doi:10.1107/s0108270190011192Roa, L., Chervin, J. C., Chevy, A., Davila, M., Grima, P., & Gonzáez, J. (1996). Optical Absorption and Raman Scattering Measurements in CuAlSe2 at High Pressure. physica status solidi (b), 198(1), 99-104. doi:10.1002/pssb.222198011

High-pressure Raman scattering study of defect chalcopyrite and defect stannite ZnGa2Se4

High-pressure Raman scattering measurements have been carried out in ZnGa2Se4 for both tetragonal defect chalcopyrite and defect stannite structures. Experimental results have been compared with theoretical lattice dynamics ab initio calculations and confirm that both phases exhibit different Raman-active phonons with slightly different pressure dependence. A pressure-induced phase transition to a Raman-inactive phase occurs for both phases; however, the sample with defect chalcopyrite structure requires slightly higher pressures than the sample with defect stannite structure to fully transform into the Raman-inactive phase. On downstroke, the Raman-inactive phase transforms into a phase that could be attributed to a disordered zincblende structure for both original phases; however, the sample with original defect chalcopyrite structure compressed just above 20¿GPa, where the transformation to the Raman-inactive phase is not completed, returns on downstroke mainly to its original structure but shows a new peak that does not correspond to the defect chalcopyrite phase. The pressure dependence of the Raman spectra with this new peak and those of the disordered zincblende phase is also reported and discussed. © 2013 AIP Publishing LLCThis study was supported by the Spanish government MEC under Grants No. MAT2010-21270-C04-01/03/04, by MALTA Consolider Ingenio 2010 project (CSD2007-00045), and by the Vicerrectorado de Investigacion y Desarrollo of the Universitat Politecnica de Valencia (UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11). E.P.-G., A.M., and P.R.-H. acknowledge computing time provided by Red Espanola de Supercomputacion (RES) and MALTA-Cluster.Vilaplana Cerda, RI.; Gomis Hilario, O.; Pérez-González, E.; Ortiz, HM.; Manjón Herrera, FJ.; Rodríguez-Hernández, P.; Muñoz, A.... (2013). High-pressure Raman scattering study of defect chalcopyrite and defect stannite ZnGa2Se4. Journal of Applied Physics. 113:2335011-23350110. https://doi.org/10.1063/1.4810854S233501123350110113A. MacKinnon, Tables of Numerical Data and Functional Relationships in Science and Technology, Landolt-Börnstein New Series, Group III, Vol. 17, pt. h, edited by O. Madelung, M. Schulz, and H. Weiss, (Springer-Verlag, Berlin, 1985), p. 124.Bernard, J. E., & Zunger, A. (1988). Ordered-vacancy-compound semiconductors: PseudocubicCdIn2Se4. Physical Review B, 37(12), 6835-6856. doi:10.1103/physrevb.37.6835Jiang, X., & Lambrecht, W. R. L. (2004). Electronic band structure of ordered vacancy defect chalcopyrite compounds with formulaII−III2−VI4. Physical Review B, 69(3). doi:10.1103/physrevb.69.035201Yahia, I. S., Fadel, M., Sakr, G. B., & Shenouda, S. S. (2010). Memory switching of ZnGa2Se4 thin films as a new material for phase change memories (PCMs). Journal of Alloys and Compounds, 507(2), 551-556. doi:10.1016/j.jallcom.2010.08.021Yahia, I. S., Fadel, M., Sakr, G. B., Yakuphanoglu, F., Shenouda, S. S., & Farooq, W. A. (2011). Analysis of current–voltage characteristics of Al/p-ZnGa2Se4/n-Si nanocrystalline heterojunction diode. Journal of Alloys and Compounds, 509(12), 4414-4419. doi:10.1016/j.jallcom.2011.01.068Hahn, H., Frank, G., Klingler, W., St�rger, A. D., & St�rger, G. (1955). Untersuchungen �ber tern�re Chalkogenide. VI. �ber Tern�re Chalkogenide des Aluminiums, Galliums und Indiums mit Zink, Cadmium und Quecksilber. Zeitschrift f�r anorganische und allgemeine Chemie, 279(5-6), 241-270. doi:10.1002/zaac.19552790502Errandonea, D., Kumar, R. S., Manjón, F. J., Ursaki, V. V., & Tiginyanu, I. M. (2008). High-pressure x-ray diffraction study on the structure and phase transitions of the defect-stannite ZnGa2Se4 and defect-chalcopyrite CdGa2S4. Journal of Applied Physics, 104(6), 063524. doi:10.1063/1.2981089Hanada, T., Izumi, F., Nakamura, Y., Nittono, O., Huang, Q., & Santoro, A. (1997). Neutron and electron diffraction studies of ZnGa2Se4. Physica B: Condensed Matter, 241-243, 373-375. doi:10.1016/s0921-4526(97)00592-9Morón, M. C., & Hull, S. (2003). Order-disorder phase transition inZn1−xMnxGa2Se4: Long-range order parameter versusx. Physical Review B, 67(12). doi:10.1103/physrevb.67.125208Morón, M. C., & Hull, S. (2005). Effect of magnetic dilution in Zn1−xMnxGa2Se4 (03.0.co;2-2Bilz, H., & Kress, W. (1979). Phonon Dispersion Relations in Insulators. Springer Series in Solid-State Sciences. doi:10.1007/978-3-642-81347-4Grzechnik, A., Ursaki, V. V., Syassen, K., Loa, I., Tiginyanu, I. M., & Hanfland, M. (2001). Pressure-Induced Phase Transitions in Cadmium Thiogallate CdGa2Se4. Journal of Solid State Chemistry, 160(1), 205-211. doi:10.1006/jssc.2001.9224Meenakshi, S., Vijyakumar, V., Godwal, B. K., Eifler, A., Orgzall, I., Tkachev, S., & Hochheimer, H. D. (2006). High pressure X-ray diffraction study of CdAl2Se4 and Raman study of AAl2Se4 (A=Hg, Zn) and CdAl2X4 (X=Se, S). Journal of Physics and Chemistry of Solids, 67(8), 1660-1667. doi:10.1016/j.jpcs.2006.02.015Meenakshi, S., Vijayakumar, V., Eifler, A., & Hochheimer, H. D. (2010). Pressure-induced phase transition in defect Chalcopyrites HgAl2Se4 and CdAl2S4. Journal of Physics and Chemistry of Solids, 71(5), 832-835. doi:10.1016/j.jpcs.2010.02.007Gomis, O., Vilaplana, R., Manjón, F. J., Santamaría-Pérez, D., Errandonea, D., Pérez-González, E., … Ursaki, V. V. (2013). Crystal structure of HgGa2Se4 under compression. Materials Research Bulletin, 48(6), 2128-2133. doi:10.1016/j.materresbull.2013.02.037A̧lvarez-Garcı́a, J., Pérez-Rodrı́guez, A., Barcones, B., Romano-Rodrı́guez, A., Morante, J. R., Janotti, A., … Scheer, R. (2002). Polymorphism in CuInS2 epilayers: Origin of additional Raman modes. Applied Physics Letters, 80(4), 562-564. doi:10.1063/1.1435800Stanbery, B. J., Kincal, S., Kim, S., Chang, C. H., Ahrenkiel, S. P., Lippold, G., … Crisalle, O. D. (2002). Epitaxial growth and characterization of CuInSe2 crystallographic polytypes. Journal of Applied Physics, 91(6), 3598-3604. doi:10.1063/1.1446234Su, D. S., & Wei, S.-H. (1999). Transmission electron microscopy investigation and first-principles calculation of the phase stability in epitaxial CuInS2 and CuGaSe2 films. Applied Physics Letters, 74(17), 2483-2485. doi:10.1063/1.12301

Elastic Mid-Infrared Light Scattering: a Basis for Microscopy of Large-Scale Electrically Active Defects in Semiconducting Materials

A method of the mid-IR-laser microscopy has been proposed for the investigation of the large-scale electrically and recombination active defects in semiconductors and non-destructive inspection of semiconductor materials and structures in the industries of microelectronics and photovoltaics. The basis for this development was laid with a wide cycle of the investigations on the low-angle mid-IR-light scattering in semiconductors. The essence of the technical idea was to apply the dark-field method for spatial filtering of the scattered light in the scanning mid-IR-laser microscope. This approach enabled the visualization of large-scale electrically active defects which are the regions enriched with ionized electrically active centers. The photoexcitation of excess carriers within a small volume located in the probe mid-IR-laser beam enabled the visualization of the large-scale recombination-active defects like those revealed in the optical or electron beam induced current methods. Both these methods of the scanning mid-IR-laser microscopy are now introduced in detail in the present paper as well as a summary of techniques used in the standard method of the lowangle mid-IR-light scattering itself. Besides the techniques for direct observations, methods for analyses of the defect composition associated with the mid-IR-laser microscopy are also discussed in the paper.Comment: 44 pages, 13 figures. A good oldi

Vibrational study of HgGa2S4 under high pressure

In this work, we report on high-pressure Raman scattering measurements in mercury digallium sulfide (HgGa2S4) with defect chalcopyrite structure that have been complemented with lattice dynamics ab initio calculations. Our measurements evidence that this semiconductor exhibits a pressure-induced phase transition from the completely ordered defect chalcopyrite structure to a partially disordered defect stannite structure above 18&#8201;GPa which is prior to the transition to the completely disordered rocksalt phase above 23&#8201;GPa. Furthermore, a completely disordered zincblende phase is observed below 5&#8201;GPa after decreasing pressure from 25&#8201;GPa. The disordered zincblende phase undergoes a reversible pressure-induced phase transition to the disordered rocksalt phase above 18&#8201;GPa. The sequence of phase transitions here reported for HgGa2S4 evidence the existence of an intermediate phase with partial cation-vacancy disorder between the ordered defect chalcopyrite and the disordered rocksalt phases and the irreversibility of the pressure-induced order-disorder processes occurring in ordered-vacancy compounds. The pressure dependence of the Raman modes of all phases, except the Raman-inactive disordered rocksalt phase, have been measured and discussed.This study was supported by the Spanish government MEC under Grant No: MAT2010-21270-C04-01/03/04, by MALTA Consolider Ingenio 2010 project (CSD2007-00045), and by the Vicerrectorado de Investigacion y Desarrollo of the Universidad Politecnica de Valencia (UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11). E. P.-G., P. R.-H., and A. M. acknowledge computing time provided by Red Espanola de Supercomputacion (RES) and MALTA-Cluster. J.A.S. acknowledges Juan de la Cierva fellowship program for his financial support.Vilaplana Cerda, RI.; Robledillo, M.; Gomis Hilario, O.; Sans, J.; Manjón Herrera, FJ.; Pérez-González, E.; Rodríguez-Hernández, P.... (2013). Vibrational study of HgGa2S4 under high pressure. Journal of Applied Physics. 113(9):935121-9351210. https://doi.org/10.1063/1.4794096S93512193512101139A. MacKinnon, inTables of Numerical Data and Functional Relationships in Science and Technology, edited by O. Madelung, M. Schulz, and H. Weiss (Springer-Verlag, Berlin, 1985), Vol. 17, p. 124.Bernard, J. E., & Zunger, A. (1988). Ordered-vacancy-compound semiconductors: PseudocubicCdIn2Se4. Physical Review B, 37(12), 6835-6856. doi:10.1103/physrevb.37.6835Jiang, X., & Lambrecht, W. R. L. (2004). Electronic band structure of ordered vacancy defect chalcopyrite compounds with formulaII−III2−VI4. Physical Review B, 69(3). doi:10.1103/physrevb.69.035201Hahn, H., Frank, G., Klingler, W., St�rger, A. D., & St�rger, G. (1955). Untersuchungen �ber tern�re Chalkogenide. VI. �ber Tern�re Chalkogenide des Aluminiums, Galliums und Indiums mit Zink, Cadmium und Quecksilber. Zeitschrift f�r anorganische und allgemeine Chemie, 279(5-6), 241-270. doi:10.1002/zaac.19552790502Schwer, H., & Krämer, V. (1990). The crystal structures of CdAl2S4, HgAl2S4, and HgGa2S4. Zeitschrift für Kristallographie, 190(1-2), 103-110. doi:10.1524/zkri.1990.190.1-2.103Levine, B., Bethea, C., Kasper, H., & Thiel, F. (1976). Nonlinear optical susceptibility of HgGa&lt;inf&gt;2&lt;/inf&gt;S&lt;inf&gt;4&lt;/inf&gt; IEEE Journal of Quantum Electronics, 12(6), 367-368. doi:10.1109/jqe.1976.1069169Ursaki, V. ., Ricci, P. ., Tiginyanu, I. ., Anedda, A., Syrbu, N. ., & Tezlevan, V. . (2002). Excitation and temperature tuned photoluminescence in HgGa 2 S 4 single crystals. Journal of Physics and Chemistry of Solids, 63(10), 1823-1828. doi:10.1016/s0022-3697(02)00002-1Rotermund, F., Petrov, V., & Noack, F. (2000). Difference-frequency generation of intense femtosecond pulses in the mid-IR (4–12 μm) using HgGa2S4 and AgGaS2. Optics Communications, 185(1-3), 177-183. doi:10.1016/s0030-4018(00)00987-1Badikov, V. V., Kuzmin, N. V., Laptev, V. B., Malinovsky, A. L., Mitin, K. V., Nazarov, G. S., … Schebetova, N. I. (2004). A study of the optical and thermal properties of nonlinear mercury thiogallate crystals. Quantum Electronics, 34(5), 451-456. doi:10.1070/qe2004v034n05abeh002702Schunemann, P. G., & Pollak, T. M. (1997). Synthesis and growth of HgGa2S4 crystals. Journal of Crystal Growth, 174(1-4), 278-282. doi:10.1016/s0022-0248(96)01158-xRange, K.-J., Becker, W., & Weiss, A. (1968). Notizen: Über Hochdruckphasen des CdAl2S4, HgAl2S4, ZnAl2Se2, CdAl2Se4 und HgAl2Se4 mit Spinellstruktur. Zeitschrift für Naturforschung B, 23(7), 1009-1009. doi:10.1515/znb-1968-0726Burlakov, I. I., Raptis, Y., Ursaki, V. V., Anastassakis, E., & Tiginyanu, I. M. (1997). Order-disorder phase transition in CdAl2S4 under hydrostatic pressure. Solid State Communications, 101(5), 377-381. doi:10.1016/s0038-1098(96)00602-3Ursaki, V. V., Burlakov, I. I., Tiginyanu, I. M., Raptis, Y. S., Anastassakis, E., & Anedda, A. (1999). Phase transitions in defect chalcopyrite compounds under hydrostatic pressure. Physical Review B, 59(1), 257-268. doi:10.1103/physrevb.59.257Meenakshi, S., Vijyakumar, V., Godwal, B. K., Eifler, A., Orgzall, I., Tkachev, S., & Hochheimer, H. D. (2006). High pressure X-ray diffraction study of CdAl2Se4 and Raman study of AAl2Se4 (A=Hg, Zn) and CdAl2X4 (X=Se, S). Journal of Physics and Chemistry of Solids, 67(8), 1660-1667. doi:10.1016/j.jpcs.2006.02.015Meenakshi, S., Vijayakumar, V., Eifler, A., & Hochheimer, H. D. (2010). Pressure-induced phase transition in defect Chalcopyrites HgAl2Se4 and CdAl2S4. Journal of Physics and Chemistry of Solids, 71(5), 832-835. doi:10.1016/j.jpcs.2010.02.007Garbato, L., Ledda, F., & Rucci, A. (1987). 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High-pressure optical and vibrational properties of CdGa2Se4: Order-disorder processes in adamantine compounds. Journal of Applied Physics, 111(1), 013518. doi:10.1063/1.3675162Eifler, A., Hecht, J.-D., Lippold, G., Riede, V., Grill, W., Krauß, G., & Krämer, V. (1999). Combined infrared and Raman study of the optical phonons of defect chalcopyrite single crystals. Physica B: Condensed Matter, 263-264, 806-808. doi:10.1016/s0921-4526(98)01292-7Eifler, A., Krauss, G., Riede, V., Krämer, V., & Grill, W. (2005). Optical phonon modes and structure of ZnGa2Se4 and ZnGa2S4. Journal of Physics and Chemistry of Solids, 66(11), 2052-2057. doi:10.1016/j.jpcs.2005.09.049Baroni, S., de Gironcoli, S., Dal Corso, A., & Giannozzi, P. (2001). Phonons and related crystal properties from density-functional perturbation theory. Reviews of Modern Physics, 73(2), 515-562. doi:10.1103/revmodphys.73.515Giannozzi, P., Baroni, S., Bonini, N., Calandra, M., Car, R., Cavazzoni, C., … Wentzcovitch, R. M. (2009). 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Directional Dispersion of the Phonon Modes in Optically Uniaxial Solids, Far-Infrared Reflection Spectra, Dielectric and Optic Constants, Dynamic Effective Ionic Charges of the Defect Chalcopyrites CdGa2S4, CdGa2Se4, HgGa2S4, and HgGa2Se4. physica status solidi (b), 129(2), 549-558. doi:10.1002/pssb.2221290212Takahashi, Y., Namatsu, H., Machida, K., & Minegishi, K. (1993). Measurements of Diffusion Coefficiens of Water in Electron Cryclotron Resonance Plasma SiO2. Japanese Journal of Applied Physics, 32(Part 2, No. 3B), L431-L433. doi:10.1143/jjap.32.l431Loudon, R. (1964). The Raman effect in crystals. Advances in Physics, 13(52), 423-482. doi:10.1080/00018736400101051Alonso-Gutiérrez, P., & Sanjuán, M. L. (2008). Ordinary and extraordinary phonons and photons: Raman study of anisotropy effects in the polar modes ofMnGa2Se4. Physical Review B, 78(4). doi:10.1103/physrevb.78.045212Errandonea, D., Kumar, R. S., Manjón, F. J., Ursaki, V. V., & Tiginyanu, I. M. (2008). High-pressure x-ray diffraction study on the structure and phase transitions of the defect-stannite ZnGa2Se4 and defect-chalcopyrite CdGa2S4. Journal of Applied Physics, 104(6), 063524. doi:10.1063/1.2981089Lowe-Ma, C. K., & Vanderah, T. A. (1991). Structure of ZnGa2S4, a defect sphalerite derivative. Acta Crystallographica Section C Crystal Structure Communications, 47(5), 919-924. doi:10.1107/s0108270190011192Grzechnik, A., Ursaki, V. V., Syassen, K., Loa, I., Tiginyanu, I. M., & Hanfland, M. (2001). Pressure-Induced Phase Transitions in Cadmium Thiogallate CdGa2Se4. Journal of Solid State Chemistry, 160(1), 205-211. doi:10.1006/jssc.2001.9224Cardona, M., Kremer, R. K., Lauck, R., Siegle, G., Muñoz, A., & Romero, A. H. (2009). Electronic, vibrational, and thermodynamic properties of metacinnabarβ-HgS, HgSe, and HgTe. Physical Review B, 80(19). doi:10.1103/physrevb.80.195204Márquez, F., & Fornés, V. (1999). Synthesis and characterisation of Ga2S3 semiconductor included in zeolite Y. Solid State Communications, 112(1), 17-20. doi:10.1016/s0038-1098(99)00295-

High-pressure optical and vibrational properties of CdGa2Se4: Order-disorder processes in adamantine compounds

High-pressure optical absorption and Raman scattering measurements have been performed in defect chalcopyrite (DC) CdGa2Se4 up to 22 GPa during two pressure cycles to investigate the pressure-induced order-disorder phase transitions taking place in this ordered-vacancy compound. Our measurements reveal that on decreasing pressure from 22 GPa, the sample does not revert to the initial phase but likely to a disordered zinc blende (DZ) structure the direct bandgap and Raman-active modes of which have been measured during a second upstroke. Our measurements have been complemented with electronic structure and lattice dynamical ab initio calculations. Lattice dynamical calculations have helped us to discuss and assign the symmetries of the Raman modes of the DC phase. Additionally, our electronic band structure calculations have helped us in discussing the order-disorder effects taking place above 6¿8 GPa during the first upstroke. © 2012 American Institute of PhysicsThis study was supported by the Spanish government MICINN under Grant No. MAT2010-21270-C04-01/03/04; by the Generalitat Valenciana (Project No. GV06/151), by MALTA Consolider Ingenio 2010 project (CSD2007-00045), by the Vicerrectorado de Investigacion y Desarrollo of the Universitat Politecnica de Valencia (UPV2012-1469), and by the Spanish MICINN under Project No. CTQ2009-14596-C02-01 and Comunidad de Madrid and the European Social Fund Grant No. S2009/PPQ-1551 4161893 (QUI-MAPRES). E.P-G., J.L-S., A. M., and P.R-H. acknowledge computing time provided by Red Espanola de Supercomputacion (RES) and MALTA-Cluster.Gomis Hilario, O.; Vilaplana Cerda, RI.; Manjón Herrera, FJ.; Pérez-González, E.; López-Solano, J.; Rodríguez-Hernández, P.; Muñoz, A.... (2012). High-pressure optical and vibrational properties of CdGa2Se4: Order-disorder processes in adamantine compounds. Journal of Applied Physics. 111(1):135181-1351815. https://doi.org/10.1063/1.3675162S13518113518151111A. MacKinnon, in Tables of Numerical Data and Functional Relationships in Science and Technology, edited by O. Madelung, M. Schulz, and H. Weiss (Springer-Verlag, Berlin, 1985), Vol. 17, p. 124.Bernard, J. E., & Zunger, A. (1988). Ordered-vacancy-compound semiconductors: PseudocubicCdIn2Se4. Physical Review B, 37(12), 6835-6856. doi:10.1103/physrevb.37.6835Jiang, X., & Lambrecht, W. R. L. (2004). Electronic band structure of ordered vacancy defect chalcopyrite compounds with formulaII−III2−VI4. Physical Review B, 69(3). doi:10.1103/physrevb.69.035201Zunger, A., Wagner, S., & Petroff, P. M. (1993). New materials and structures for photovoltaics. Journal of Electronic Materials, 22(1), 3-16. doi:10.1007/bf02665719Morón, M. C., & Hull, S. (2003). Order-disorder phase transition inZn1−xMnxGa2Se4: Long-range order parameter versusx. Physical Review B, 67(12). doi:10.1103/physrevb.67.125208Joshi, N. V., Luengo, J., & Vera, F. (2007). Optical activity in []ZnGa2S4. Materials Letters, 61(8-9), 1926-1928. doi:10.1016/j.matlet.2006.07.177Krämer, V., Siebert, D., & Febbraro, S. (1984). Structure refinement of cadmium gallium selenide CdGa2Se4. Zeitschrift für Kristallographie, 169(1-4), 283-287. doi:10.1524/zkri.1984.169.1-4.283Gastaldi, L., Simeone, M. G., & Viticoli, S. (1985). Cation ordering and crystal structures in AGa2X4 compounds (CoGa2S4, CdGa2S4, CdGa2Se4, HgGa2Se4, HgGa2Te4). Solid State Communications, 55(7), 605-607. doi:10.1016/0038-1098(85)90821-xUrsaki, V. V., Burlakov, I. I., Tiginyanu, I. M., Raptis, Y. S., Anastassakis, E., & Anedda, A. (1999). Phase transitions in defect chalcopyrite compounds under hydrostatic pressure. Physical Review B, 59(1), 257-268. doi:10.1103/physrevb.59.257Mitani, T., Naitou, T., Matsuishi, K., Onari, S., Allakhverdiev, K., Gashimzade, F., & Kerimova, T. (2003). Raman scattering in CdGa2Se4 under pressure. physica status solidi (b), 235(2), 321-325. doi:10.1002/pssb.200301579Fuentes-Cabrera, M. (2001). Ab initiostudy of the vibrational and electronic properties of CdGa2S4and CdGa2Se4under pressure. Journal of Physics: Condensed Matter, 13(45), 10117-10124. doi:10.1088/0953-8984/13/45/301Fuentes-Cabrera, M., & Sankey, O. F. (2001). Theoretical study of the ordered-vacancy semiconducting compound CdAl2Se4. Journal of Physics: Condensed Matter, 13(8), 1669-1684. doi:10.1088/0953-8984/13/8/305Grzechnik, A., Ursaki, V. V., Syassen, K., Loa, I., Tiginyanu, I. M., & Hanfland, M. (2001). Pressure-Induced Phase Transitions in Cadmium Thiogallate CdGa2Se4. Journal of Solid State Chemistry, 160(1), 205-211. doi:10.1006/jssc.2001.9224Manjón, F. J., Gomis, O., Rodríguez-Hernández, P., Pérez-González, E., Muñoz, A., Errandonea, D., … Ursaki, V. V. (2010). Nonlinear pressure dependence of the direct band gap in adamantine ordered-vacancy compounds. Physical Review B, 81(19). doi:10.1103/physrevb.81.195201Eifler, A., Hecht, J.-D., Lippold, G., Riede, V., Grill, W., Krauß, G., & Krämer, V. (1999). Combined infrared and Raman study of the optical phonons of defect chalcopyrite single crystals. Physica B: Condensed Matter, 263-264, 806-808. doi:10.1016/s0921-4526(98)01292-7Eifler, A., Krauss, G., Riede, V., Krämer, V., & Grill, W. (2005). Optical phonon modes and structure of ZnGa2Se4 and ZnGa2S4. Journal of Physics and Chemistry of Solids, 66(11), 2052-2057. doi:10.1016/j.jpcs.2005.09.049Burlakov, I. I., Raptis, Y., Ursaki, V. V., Anastassakis, E., & Tiginyanu, I. M. (1997). Order-disorder phase transition in CdAl2S4 under hydrostatic pressure. 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High-pressure study of the structural and elastic properties of defect-chalcopyrite HgGa2Se4

In this work, we focus on the study of the structural and elastic properties of mercury digallium selenide (HgGa2Se4) which belongs to the family of AB 2 X 4 ordered-vacancy compounds with tetragonal defect chalcopyrite structure. We have carried out high-pressure x-ray diffraction measurements up to 13.2¿GPa. Our measurements have been complemented and compared with total-energy ab initio calculations. The equation of state and the axial compressibilities for the low-pressure phase of HgGa2Se4 have been experimentally and theoretically determined and compared to other related ordered-vacancy compounds. The theoretical cation-anion and vacancy-anion distances in HgGa2Se4 have been determined. The internal distance compressibility in HgGa2Se4 has been compared with those that occur in binary HgSe and ¿¿GaSe compounds. It has been found that the Hg-Se and Ga-Se bonds behave in a similar way in the three compounds. It has also been found that bulk compressibility of the compounds decreases following the sequence ¿¿-GaSe¿>¿HgGa2Se4¿>¿HgSe.¿ Finally, we have studied the pressure dependence of the theoretical elastic constants and elastic moduli of HgGa2Se4. Our calculations report that the low-pressure phase of HgGa2Se4 becomes mechanically unstable above 13.3 GPa.. © 2013 American Institute of PhysicsGomis Hilario, O.; Vilaplana Cerda, RI.; Manjón Herrera, FJ.; Santamaría-Pérez, D.; Errandonea, D.; Pérez-González, E.; López-Solano, J.... (2013). High-pressure study of the structural and elastic properties of defect-chalcopyrite HgGa2Se4. Journal of Applied Physics. 113(1):735101-7351010. doi:10.1063/1.4792495 http://jap.aip.org/resource/1/japiau/v113/i7/p073510_s1S7351017351010113