High-pressure Raman investigation of high index facets bounded alpha-Fe2O3 pseudocubic crystals

[EN] High index facet bounded alpha-Fe2O3 pseudocubic crystals has gained the attention of the scientific community due to its promising electrochemical sensing response towards aqueous ammonia. The structural stability of alpha-Fe2O3 pseudocubic crystals is investigated through high-pressure Raman spectroscopy up to 22.2 GPa, and those results are compared with our ab initio theoretical calculations. The symmetry of the experimental Raman-active modes has been assigned by comparison with theoretical data. In addition to the Raman-active modes, two additional Raman features are also detected, whose intensity increases with compression. The origin of these two additional peaks addressed in this study, reveals a strong dependence on the geometry and the low dimensionality as the most plausible explanationNeravathu G Divya acknowledges DST FIST for FESEM analysis, Department of Physics, Cochin University of Science and Technology, Kerala, India. The author also acknowledges the Sophisticated Test and Instrumentation Centre (STIC), Kochi, India, for Rietveld Refinement measurements. This work is partly supported by Spanish MINECO under the projects MAT2016-75586-C4-2/3-P, FIS2017-83295-P, and MALTA Consolider Team project (RED2018-102612-T), and also by Generalitat Valenciana under project PROMETEO/2018/123-EFIMAT. JAS acknowledges the Ramon y Cajal program for funding supports through RYC-2015-17482 and VM to the Juan de la Cierva program through FJCI-2016-27921.Bushiri, MJ.; Gopi, DN.; Monteseguro, V.; Sans-Tresserras, JÁ. (2021). High-pressure Raman investigation of high index facets bounded alpha-Fe2O3 pseudocubic crystals. Journal of Physics Condensed Matter. 33(8):1-10. https://doi.org/10.1088/1361-648X/abcb11S11033

SnS Thin Films Prepared by Chemical Spray Pyrolysis at Different Substrate Temperatures for Photovoltaic Applications

[EN] The preparation and analysis of morphological, structural, optical, vibrational and compositional properties of tin monosulfide (SnS) thin films deposited on glass substrate by chemical spray pyrolysis is reported herein. The growth conditions were evaluated to reduce the presence of residual phases different to the SnS orthorhombic phase. X-ray diffraction spectra revealed the polycrystalline nature of the SnS films with orthorhombic structure and a preferential grain orientation along the (111) direction. At high substrate temperature (450A degrees C), a crystalline phase corresponding to the Sn2S3 phase was observed. Raman spectroscopy confirmed the dominance of the SnS phase and the presence of an additional Sn2S3 phase. Scanning electron microscopy (SEM) images reveal that the SnS film morphology depends on the substrate temperature. Between 250A degrees C and 350A degrees C, SnS films were shaped as rounded grains with some cracks between them, while at substrate temperatures above 400A degrees C, films were denser and more compact. Energy-dispersive x-ray spectroscopy (EDS) analysis showed that the stoichiometry of sprayed SnS films improved with the increase of substrate temperature and atomic force microscopy micrographs showed films well covered at 350A degrees C resulting in a rougher and bigger grain size. Optical and electrical measurements showed that the optical bandgap and the resistivity decreased when the substrate temperature increased, and smaller values, 1.46 eV and 60 Omega cm, respectively, were attained at 450A degrees C. These SnS thin films could be used as an absorber layer for the development of tandem solar cell devices due to their high absorbability in the visible region with optimum bandgap energy.This work was supported by Ministerio de Economia y Competitividad (ENE2013-46624-C4-4-R) and Generalitat valenciana (Prometeus 2014/044).Sall, T.; Marí, B.; Mollar García, MA.; Sans-Tresserras, JÁ. (2017). SnS Thin Films Prepared by Chemical Spray Pyrolysis at Different Substrate Temperatures for Photovoltaic Applications. Journal of Electronic Materials. 46(3):1714-1719. https://doi.org/10.1007/s11664-016-5215-9S17141719463N.R. Mathews, H.B.M. Anaya, M.A. Cortes-Jacome, C. Angeles-Chavez, and J.A. Toledo-Antonio, J. Electrochem. Soc. 157, H337 (2010).N. Koteeswara Reddy, K. Ramesh, R. Ganesan, K. Reddy, K.R. Gunasekhar, and E. Gopal, Appl. Phys. A 83, 133 (2006).J.J. Loferski, J. Appl. Phys. 27, 777 (1956).K.T.R. Reddy, N.K. Reddy, and R.W. Miles, Sol. Energy Mat. Sol. C 90, 3041 (2006).C. Gao, H.L. Shen, L. Sun, H.B. Huang, L.F. Lu, and H. Cai, Mater. Lett. 64, 2177 (2010).D. Avellaneda, M.T.S. Nair, and P.K. Nair, J. Electrochem. Soc. 155, D517 (2008).J.R.S. Brownson, C. Georges, and C. Levy-Clement, Chem. Mater. 19, 3080 (2007).P. Sinsermsuksakul, J. Heo, W. Noh, A.S. Hock, and R.G. Gordon, Adv. Eng. Mat 1, 1116 (2011).T. Sall, M. Mollar, and B. Marí, J. Mater. Sci. 51, 7607 (2016).K. Otto, A. Katerski, O. Volobujeva, A. Mere, and M. Krunks, Energy Proc. 3, 63 (2011).J. Malaquias, P.A. Fernandes, P.M.P. Salomé, and A.F. da Cunha, Thin Solid Films 519, 7416 (2011).T.H. Sajeesh, A.R. Warrier, C. Sudha Kartha, and K.P. Vijayakumar, Thin Solid Films 518, 4370 (2010).M. Vasudeva Reddy, G. Sreedevi, C. Park, R.W. Miles, and K.T. Ramakrishna Reddy, Curr. Appl. Phys. 15, 588 (2015).A. Molenaar, Extended Abstracts, vol. 84-2, Pennington, N.J., 634 (1984)S. López, S. Granados, and A. Ortiz, Semicond. Sci. Technol. 11, 433 (1996).B. Cullity, Elements of X-ray Diffraction (New York: Addision-Wesley Publishing Company Inc, 1967), p. 501.G. Willeke, R. Dasbach, B. Sailer, and E. Bucher, Thin Solid Films 213, 271 (1992).H.R. Chandrasekhar, R.G. Humphreys, U. Zwick, and M. Cardona, Phys. Rev. B 15, 2177 (1977).S. Cheng and G. Conibeer, Thin Solid Films 520, 837 (2011)

Combined Experimental and Theoretical Studies: Lattice-Dynamical Studies at High Pressures with the Help of Ab Initio Calculations

[EN] Lattice dynamics studies are important for the proper characterization of materials, since these studies provide information on the structure and chemistry of materials via their vibrational properties. These studies are complementary to structural characterization, usually by means of electron, neutron, or X-ray diffraction measurements. In particular, Raman scattering and infrared absorption measurements are very powerful, and are the most common and easy techniques to obtain information on the vibrational modes at the Brillouin zone center. Unfortunately, many materials, like most minerals, cannot be obtained in a single crystal form, and one cannot play with the different scattering geometries in order to make a complete characterization of the Raman scattering tensor of the material. For this reason, the vibrational properties of many materials, some of them known for millennia, are poorly known even under room conditions. In this paper, we show that, although it seems contradictory, the combination of experimental and theoretical studies, like Raman scattering experiments conducted at high pressure and ab initio calculations, is of great help to obtain information on the vibrational properties of materials at different pressures, including at room pressure. The present paper does not include new experimental or computational results. Its focus is on stressing the importance of combined experimental and computational approaches to understand materials properties. For this purpose, we show examples of materials already studied in different fields, including some hot topic areas such as phase change materials, thermoelectric materials, topological insulators, and new subjects as metavalent bonding.This publication is part of the project MALTA Consolider Team network (RED2018-102612-T), financed by MINECO/AEI/ 10.13039/501100003329; by I+D+i projects PID2019-106383GB-42/43 and FIS2017-83295-P, financed by MCIN/AEI/10.13039/501100011033; by project PROMETEO/2018/123 (EFIMAT), financed by Generalitat Valenciana. J.A.S. acknowledges the Ramon y Cajal fellowship (RYC-2015-17482) for financial support.Manjón, F.; Sans-Tresserras, JÁ.; Rodríguez-Hernández, P.; Muñoz, A. (2021). Combined Experimental and Theoretical Studies: Lattice-Dynamical Studies at High Pressures with the Help of Ab Initio Calculations. Minerals. 11(11):1-17. https://doi.org/10.3390/min11111283S117111

Pressure-Induced Phase Transitions in Sesquioxides

[EN] Pressure is an important thermodynamic parameter, allowing the increase of matter density by reducing interatomic distances that result in a change of interatomic interactions. In this context, the long range in which pressure can be changed (over six orders of magnitude with respect to room pressure) may induce structural changes at a much larger extent than those found by changing temperature or chemical composition. In this article, we review the pressure-induced phase transitions of most sesquioxides, i.e., A(2)O(3) compounds. Sesquioxides constitute a big subfamily of ABO(3) compounds, due to their large diversity of chemical compositions. They are very important for Earth and Materials Sciences, thanks to their presence in our planet's crust and mantle, and their wide variety of technological applications. Recent discoveries, hot spots, controversial questions, and future directions of research are highlighted.This research was funded by Spanish Ministerio de Ciencia, Innovacion y Universidades under grants MAT2016-75586-C4-1/2/3-P, FIS2017-83295-P, PGC2018-094417-B-100, and RED2018-102612-T (MALTA-Consolider-Team network) and by Generalitat Valenciana under grant PROMETEO/2018/123 (EFIMAT). J. A. S. also acknowledges Ramon y Cajal Fellowship for financial support (RYC-2015-17482).Manjón, F.; Sans-Tresserras, JÁ.; Ibáñez, J.; Pereira, ALDJ. (2019). Pressure-Induced Phase Transitions in Sesquioxides. Crystals. 9(12):1-32. https://doi.org/10.3390/cryst9120630S132912Adachi, G., & Imanaka, N. (1998). The Binary Rare Earth Oxides. Chemical Reviews, 98(4), 1479-1514. doi:10.1021/cr940055hZINKEVICH, M. (2007). Thermodynamics of rare earth sesquioxides. Progress in Materials Science, 52(4), 597-647. doi:10.1016/j.pmatsci.2006.09.002Manjón, F. J., & Errandonea, D. (2008). 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T., Wentzcovitch, R. M., & Bukowinski, M. S. T. (1996). Polymorphs of Alumina Predicted by First Principles: Putting Pressure on the Ruby Pressure Scale. Science, 274(5294), 1880-1882. doi:10.1126/science.274.5294.1880Jahn, S., Madden, P., & Wilson, M. (2004). Dynamic simulation of pressure-driven phase transformations in crystalline Al2O3. Physical Review B, 69(2). doi:10.1103/physrevb.69.020106Tsuchiya, J., Tsuchiya, T., & Wentzcovitch, R. M. (2005). Transition from theRh2O3(II)-to-CaIrO3structure and the high-pressure-temperature phase diagram of alumina. Physical Review B, 72(2). doi:10.1103/physrevb.72.020103García-Domene, B., Sans, J. A., Gomis, O., Manjón, F. J., Ortiz, H. M., Errandonea, D., … Segura, A. (2014). Pbca-Type In2O3: The High-Pressure Post-Corundum phase at Room Temperature. The Journal of Physical Chemistry C, 118(35), 20545-20552. doi:10.1021/jp5061599Yusa, H., Tsuchiya, T., Sata, N., & Ohishi, Y. (2008). Rh2O3(II)-type structures inGa2O3andIn2O3under high pressure: Experiment and theory. Physical Review B, 77(6). doi:10.1103/physrevb.77.064107Sans, J. A., Vilaplana, R., Errandonea, D., Cuenca-Gotor, V. P., García-Domene, B., Popescu, C., … Muñoz, A. (2017). Structural and vibrational properties of corundum-type In2O3nanocrystals under compression. Nanotechnology, 28(20), 205701. doi:10.1088/1361-6528/aa6a3fLipinska-Kalita, K. E., Chen, B., Kruger, M. B., Ohki, Y., Murowchick, J., & Gogol, E. P. (2003). High-pressure x-ray diffraction studies of the nanostructured transparent vitroceramic mediumK2O−SiO2−Ga2O3. Physical Review B, 68(3). doi:10.1103/physrevb.68.035209Luan, S., Dong, L., & Jia, R. (2019). Analysis of the structural, anisotropic elastic and electronic properties of β-Ga2O3 with various pressures. Journal of Crystal Growth, 505, 74-81. doi:10.1016/j.jcrysgro.2018.09.031Machon, D., McMillan, P. F., Xu, B., & Dong, J. (2006). High-pressure study of theβ-to-αtransition inGa2O3. Physical Review B, 73(9). doi:10.1103/physrevb.73.094125Wang, H., He, Y., Chen, W., Zeng, Y. W., Stahl, K., Kikegawa, T., & Jiang, J. Z. (2010). High-pressure behavior of β-Ga2O3 nanocrystals. Journal of Applied Physics, 107(3), 033520. doi:10.1063/1.3296121Claussen, W. F., & Mackenzie, J. D. (1959). CRYSTALLIZATION OF B2O3AT HIGH PRESSURES1. Journal of the American Chemical Society, 81(4), 1007-1007. doi:10.1021/ja01513a063Brazhkin, V. V., Katayama, Y., Inamura, Y., Kondrin, M. V., Lyapin, A. G., Popova, S. V., & Voloshin, R. N. (2003). Structural transformations in liquid, crystalline, and glassy B2O3 under high pressure. Journal of Experimental and Theoretical Physics Letters, 78(6), 393-397. doi:10.1134/1.1630134Nicholas, J., Sinogeikin, S., Kieffer, J., & Bass, J. (2004). Spectroscopic Evidence of Polymorphism in VitreousB2O3. Physical Review Letters, 92(21). doi:10.1103/physrevlett.92.215701Lee, S. 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(2017). Investigation of the Production of β-Al2O3 Solid Electrolyte from Seydişehir α-Al2O3. Süleyman Demirel Üniversitesi Fen Bilimleri Enstitüsü Dergisi, 21(3), 816. doi:10.19113/sdufbed.31721Duan, W., Wentzcovitch, R. M., & Thomson, K. T. (1998). First-principles study of high-pressure alumina polymorphs. Physical Review B, 57(17), 10363-10369. doi:10.1103/physrevb.57.10363Oganov, A. R., & Ono, S. (2005). The high-pressure phase of alumina and implications for Earth’s D’’ layer. Proceedings of the National Academy of Sciences, 102(31), 10828-10831. doi:10.1073/pnas.0501800102Hama, J., & Suito, K. (2002). The evidence for the occurrence of two successive transitions in Al2O3 from the analysis of Hugoniot data. High Temperatures-High Pressures, 34(3), 323-334. doi:10.1068/htjr033Ono, S., Kikegawa, T., & Ohishi, Y. (2004). High-pressure phase transition of hematite, Fe2O3. Journal of Physics and Chemistry of Solids, 65(8-9), 1527-1530. doi:10.1016/j.jpcs.2003.11.042Oganov, A. 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Oscillations studied with the smartphone ambient light sensor

This paper makes use of a smartphone's ambient light sensor to analyse a system of two coupled springs undergoing either simple or damped oscillatory motion. The period, frequency and stiffness of the spring, together with the damping constant and extinction time, are extracted from light intensity curves obtained using a free Android application. The results demonstrate the instructional value of mobile phone sensors as a tool in the physics laboratory.The authors would like to thank the Institute of Education Sciences, Universitat Politecnica de Valencia (Spain) for the support of the Teaching Innovation Groups, e-MACAFI and MoMa.Sans Tresserras, JÁ.; Manjón Herrera, FJ.; Pereira, A.; Gómez-Tejedor, JA.; Monsoriu Soriano, JC. (2013). Oscillations studied with the smartphone ambient light sensor. European Journal of Physics. 34(6):1349-1354. doi:10.1088/0143-0807/34/6/1349S13491354346Monsoriu, J. A., Giménez, M. H., Riera, J., & Vidaurre, A. (2005). Measuring coupled oscillations using an automated video analysis technique based on image recognition. European Journal of Physics, 26(6), 1149-1155. doi:10.1088/0143-0807/26/6/023Shamim, S., Zia, W., & Anwar, M. S. (2010). Investigating viscous damping using a webcam. American Journal of Physics, 78(4), 433-436. doi:10.1119/1.3298370Ochoa, O. R., & Kolp, N. F. (1997). The computer mouse as a data acquisition interface: Application to harmonic oscillators. American Journal of Physics, 65(11), 1115-1118. doi:10.1119/1.18732Ng, T. W., & Ang, K. T. (2005). The optical mouse for harmonic oscillator experimentation. American Journal of Physics, 73(8), 793-795. doi:10.1119/1.1862634Tomarken, S. L., Simons, D. R., Helms, R. W., Johns, W. E., Schriver, K. E., & Webster, M. S. (2012). Motion tracking in undergraduate physics laboratories with the Wii remote. American Journal of Physics, 80(4), 351-354. doi:10.1119/1.3681904Ballester, J., & Pheatt, C. (2013). Using the Xbox Kinect sensor for positional data acquisition. American Journal of Physics, 81(1), 71-77. doi:10.1119/1.4748853Vannoni, M., & Straulino, S. (2007). Low-cost accelerometers for physics experiments. European Journal of Physics, 28(5), 781-787. doi:10.1088/0143-0807/28/5/001Skeffington, A., & Scully, K. (2012). Simultaneous Tracking of Multiple Points Using a Wiimote. The Physics Teacher, 50(8), 482-484. doi:10.1119/1.4758151Castro-Palacio, J. C., Velázquez-Abad, L., Giménez, F., & Monsoriu, J. A. (2013). A quantitative analysis of coupled oscillations using mobile accelerometer sensors. European Journal of Physics, 34(3), 737-744. doi:10.1088/0143-0807/34/3/737Carlos Castro-Palacio, J., Velázquez-Abad, L., Giménez, M. H., & Monsoriu, J. A. (2013). Using a mobile phone acceleration sensor in physics experiments on free and damped harmonic oscillations. American Journal of Physics, 81(6), 472-475. doi:10.1119/1.4793438Ouseph, P. J., Driver, K., & Conklin, J. (2001). Polarization of light by reflection and the Brewster angle. American Journal of Physics, 69(11), 1166-1168. doi:10.1119/1.1397457Berger, J. (1988). On potential energy, its force field and their measurement along an air track. European Journal of Physics, 9(1), 47-50. doi:10.1088/0143-0807/9/1/00

High-pressure characterization of multifunctional CrVO4

[EN] The structural stability and physical properties of CrVO(4)under compression were studied by x-ray diffraction, Raman spectroscopy, optical absorption, resistivity measurements, andab initiocalculations up to 10 GPa. High-pressure x-ray diffraction and Raman measurements show that CrVO(4)undergoes a phase transition from the ambient pressure orthorhombic CrVO4-type structure (Cmcm space group, phase III) to the high-pressure monoclinic CrVO4-V phase, which is proposed to be isomorphic to the wolframite structure. Such a phase transition (CrVO4-type -> wolframite), driven by pressure, also was previously observed in indium vanadate. The crystal structure of both phases and the pressure dependence in unit-cell parameters, Raman-active modes, resistivity, and electronic band gap, are reported. Vanadium atoms are sixth-fold coordinated in the wolframite phase, which is related to the collapse in the volume at the phase transition. Besides, we also observed drastic changes in the phonon spectrum, a drop of the band-gap, and a sharp decrease of resistivity. All the observed phenomena are explained with the help of first-principles calculations.This work was supported by the Spanish Ministry of Science, Innovation and Universities under Grants MAT2016-75586-C4-1/2-P, FIS2017-83295-P and RED2018-102612-T (MALTA Consolider-Team network) and by Generalitat Valenciana under Grant Prometeo/2018/123 (EFIMAT). PB and AV acknowledge the Kempe Foundation and the Knut och Alice Wallenberg Foundation for their financial support. JAS also acknowledges Ramon y Cajal program for funding support through RYC-2015-17482. The x-ray diffraction measurements were carried out with the support of the Diamond Light Source at the I15 beamline under proposal no. 683. The authors thank A Kleppe for technical support during the experiments. SL-M thanks CONACYT of Mexico for financial support through the program 'Catedras para jovenes Investigadores'. Also, SL-M gratefully acknowledges the computing time granted by LANCAD and CONACYT on the supercomputer Miztli at LSVP DGTIC UNAM. Besides, some of the computing for this project was performed with the resources of the IPICYT Supercomputing National Center for Education & Research, Grant TKII-R2020-SLM1.Botella, P.; López-Moreno, S.; Errandonea, D.; Manjón, F.; Sans-Tresserras, JÁ.; Vie, D.; Vomiero, A. (2020). High-pressure characterization of multifunctional CrVO4. Journal of Physics Condensed Matter. 32(38):1-14. https://doi.org/10.1088/1361-648X/ab9408S114323

X-ray nanoimaging of Nd3+ optically active ions embedded in Sr0.5Ba0.5Nb2O6 nanocrystals

[EN] The spatial distribution of Sr0.5Ba0.5Nb2O6 nanocrystals is analyzed in a borate-based glass-ceramic by a synchrotron hard X-ray nanoimaging tool. Based on X-ray excited optical luminescence, we examined 2D projections of the Nd3+ optically active ions in the Sr0.5Ba0.5Nb2O6 nanocrystals, as well as in the glassy phase where they are embedded. Our findings reveal areas of agglomerations and/or clusters of nanocrystals ascribed to the diffusion coefficients of their constituent elements. They are characterized by high Nd3+ concentrations that may act as heterogeneous agents for the nucleation and growth of these nanocrystals. (C) 2017 Optical Society of AmericaMINECO, EU-FEDER and CSIC through the projects MAT2013-46649-C4-4-P, MAT201571070-REDC, MAT2016-75586-C4-2-P, MAT2016-75586-C4-4-P, 201550I021 and 201660I001, respectively. JAS acknowledges the Spanish Program Ramón y Cajal for his fellowship. We also thank the ESRF for the beam time allocated and experimental facilities.Martínez-Criado, G.; Alén, B.; Sans-Tresserras, JÁ.; Lozano-Gorrín, A.; Haro-González, P.; Martin, I.; Lavin, V. (2017). X-ray nanoimaging of Nd3+ optically active ions embedded in Sr0.5Ba0.5Nb2O6 nanocrystals. Optical Materials Express. 7(7):2424-2431. https://doi.org/10.1364/OME.7.002424S2424243177Nagata, K., Yamamoto, Y., Igarashi, H., & Okazaki, K. (1981). Properties of the hot-pressed strontium barium niobate ceramics. Ferroelectrics, 38(1), 853-856. doi:10.1080/00150198108209556Imai, T., Yagi, S., Yamazaki, H., & Ono, M. (1999). Effects of Heat Treatment on Photorefractive Sensitivity of Ce- and Eu-Doped Strontium Barium Niobate. Japanese Journal of Applied Physics, 38(Part 1, No. 4A), 1984-1988. doi:10.1143/jjap.38.1984Volk, T., Isakov, D., Salobutin, V., Ivleva, L., Lykov, P., Ramzaev, V., & Wöhlecke, M. (2004). Effects of Ni doping on properties of strontium–barium–niobate crystals. Solid State Communications, 130(3-4), 223-226. doi:10.1016/j.ssc.2004.01.039Romero, J. J., Andreeta, M. R. B., Andreeta, E. R. M., Bausá, L. E., Hernandes, A. C., & García Solé, J. (2004). Growth and characterization of Nd-doped SBN single crystal fibers. Applied Physics A, 78(7), 1037-1042. doi:10.1007/s00339-003-2151-3Chayapiwut, N., Honma, T., Benino, Y., Fujiwara, T., & Komatsu, T. (2005). Synthesis of Sm3+-doped strontium barium niobate crystals in glass by samarium atom heat processing. Journal of Solid State Chemistry, 178(11), 3507-3513. doi:10.1016/j.jssc.2005.09.002Haro-González, P., Martín, I. R., Martín, L. L., León-Luis, S. F., Pérez-Rodríguez, C., & Lavín, V. (2011). Characterization of Er3+ and Nd3+ doped Strontium Barium Niobate glass ceramic as temperature sensors. Optical Materials, 33(5), 742-745. doi:10.1016/j.optmat.2010.11.026Ivleva, L. I., Volk, T. R., Isakov, D. V., Gladkii, V. V., Polozkov, N. M., & Lykov, P. A. (2002). Growth and ferroelectric properties of Nd-doped strontium–barium niobate crystals. Journal of Crystal Growth, 237-239, 700-702. doi:10.1016/s0022-0248(01)01997-2Marcinkevičius, A., Juodkazis, S., Watanabe, M., Miwa, M., Matsuo, S., Misawa, H., & Nishii, J. (2001). Femtosecond laser-assisted three-dimensional microfabrication in silica. Optics Letters, 26(5), 277. doi:10.1364/ol.26.000277Sato, R., Benino, Y., Fujiwara, T., & Komatsu, T. (2001). YAG laser-induced crystalline dot patterning in samarium tellurite glasses. Journal of Non-Crystalline Solids, 289(1-3), 228-232. doi:10.1016/s0022-3093(01)00736-0Haro-González, P., Martín, L. L., González-Pérez, S., & Martín, I. R. (2010). Formation of Nd3+ doped Strontium Barium Niobate nanocrystals by two different methods. Optical Materials, 32(10), 1389-1392. doi:10.1016/j.optmat.2010.03.011Haro-González, P., Martín, I. R., & Creus, A. H. (2010). Nanocrystals distribution inside the writing lines in a glass matrix using Argon laser irradiation. Optics Express, 18(2), 582. doi:10.1364/oe.18.000582Haro-González, P., Martín, I. R., Arbelo-Jorge, E., González-Pérez, S., Cáceres, J. M., & Núñez, P. (2008). Laser irradiation in Nd3+ doped strontium barium niobate glass. Journal of Applied Physics, 104(1), 013112. doi:10.1063/1.2952011Kowalska, D., Haro-González, P., Martín, I. R., & Cáceres, J. M. (2010). Analysis of the optical properties of Er3+-doped strontium barium niobate nanocrystals using time-resolved laser spectroscopy. Applied Physics A, 99(4), 771-776. doi:10.1007/s00339-010-5716-yPellicer-Porres, J., Segura, A., Martínez-Criado, G., Rodríguez-Mendoza, U. R., & Lavín, V. (2012). Formation of nanostructures in Eu3+doped glass–ceramics: an XAS study. Journal of Physics: Condensed Matter, 25(2), 025303. doi:10.1088/0953-8984/25/2/025303Martínez-Criado, G., Alén, B., Sans, J. A., Homs, A., Kieffer, I., Tucoulou, R., … Yi, G. (2012). Spatially resolved X-ray excited optical luminescence. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 284, 36-39. doi:10.1016/j.nimb.2011.08.013Martínez-Criado, G., Sans, J. A., Segura-Ruiz, J., Tucoulou, R., Solé, A. V., Homs, A., … Alén, B. (2011). X-ray excited optical luminescence imaging of InGaN nano-LEDs. physica status solidi (c), 9(3-4), 628-630. doi:10.1002/pssc.201100430Villanova, J., Segura-Ruiz, J., Lafford, T., & Martinez-Criado, G. (2012). Synchrotron microanalysis techniques applied to potential photovoltaic materials. Journal of Synchrotron Radiation, 19(4), 521-524. doi:10.1107/s0909049512021383Smith, J., Akbari-Sharbaf, A., Ward, M. J., Murphy, M. W., Fanchini, G., & Kong Sham, T. (2013). Luminescence properties of defects in nanocrystalline ZnO. Journal of Applied Physics, 113(9), 093104. doi:10.1063/1.4794001Armelao, L., Heigl, F., Jürgensen, A., Blyth, R. I. R., Regier, T., Zhou, X.-T., & Sham, T. K. (2007). X-ray Excited Optical Luminescence Studies of ZnO and Eu-Doped ZnO Nanostructures. The Journal of Physical Chemistry C, 111(28), 10194-10200. doi:10.1021/jp071379fMartínez-Criado, G., Villanova, J., Tucoulou, R., Salomon, D., Suuronen, J.-P., Labouré, S., … Morse, J. (2016). ID16B: a hard X-ray nanoprobe beamline at the ESRF for nano-analysis. Journal of Synchrotron Radiation, 23(1), 344-352. doi:10.1107/s1600577515019839Jamieson, P. B., Abrahams, S. C., & Bernstein, J. L. (1968). Ferroelectric Tungsten Bronze‐Type Crystal Structures. I. Barium Strontium Niobate Ba0.27Sr0.75Nb2O5.78. The Journal of Chemical Physics, 48(11), 5048-5057. doi:10.1063/1.1668176Haro-González, P., Martín, I. R., & Hernández Creus, A. (2011). Nanocrystals formation on Ho3+ doped strontium barium niobate glass. Journal of Luminescence, 131(4), 657-661. doi:10.1016/j.jlumin.2010.11.011Lavı́n, V., Rodrı́guez-Mendoza, U. R., Martı́n, I. R., & Rodrı́guez, V. D. (2003). Optical spectroscopy analysis of the Eu3+ ions local structure in calcium diborate glasses. Journal of Non-Crystalline Solids, 319(1-2), 200-216. doi:10.1016/s0022-3093(02)01914-2Chernaya, T. S., Volk, T. R., Verin, I. A., Ivleva, L. I., & Simonov, V. I. (2002). Atomic structure of (Sr0.50Ba0.50)Nb2O6 single crystals in the series of (SrxBa1 − x )Nb2O6 compounds. Crystallography Reports, 47(2), 213-216. doi:10.1134/1.1466494Erbil, A., Cargill III, G. S., Frahm, R., & Boehme, R. F. (1988). Total-electron-yield current measurements for near-surface extended x-ray-absorption fine structure. Physical Review B, 37(5), 2450-2464. doi:10.1103/physrevb.37.2450Solé, V. A., Papillon, E., Cotte, M., Walter, P., & Susini, J. (2007). A multiplatform code for the analysis of energy-dispersive X-ray fluorescence spectra. Spectrochimica Acta Part B: Atomic Spectroscopy, 62(1), 63-68. doi:10.1016/j.sab.2006.12.002Martínez-Criado, G., Homs, A., Alén, B., Sans, J. A., Segura-Ruiz, J., Molina-Sánchez, A., … Yi, G.-C. (2012). Probing Quantum Confinement within Single Core–Multishell Nanowires. Nano Letters, 12(11), 5829-5834. doi:10.1021/nl303178uMartínez-Criado, G., Segura-Ruiz, J., Alén, B., Eymery, J., Rogalev, A., Tucoulou, R., & Homs, A. (2014). Exploring Single Semiconductor Nanowires with a Multimodal Hard X-ray Nanoprobe. Advanced Materials, 26(46), 7873-7879. doi:10.1002/adma.201304345Shyu, J.-J., & Wang, J.-R. (2000). Crystallization and Dielectric Properties of SrO-BaO-Nb2O5-SiO2Tungsten-Bronze Glass-Ceramics. Journal of the American Ceramic Society, 83(12), 3135-3140. doi:10.1111/j.1151-2916.2000.tb01694.

Hydrolytic stability and biocompatibility on smooth muscle cells of polyethylene glycol-polycaprolactone-based polyurethanes

[EN] Interactions between smooth muscle cells (SMCs) and biomaterials must not result in phenotype changes as this may generate uncontrolled multiplication processes and occlusions in vascular grafts. The aim of this study was to relate the hydrolytic stability and biocompatibility of polyurethanes (PUs) on SMCs. A higher polycaprolactone (PCL) concentration was found to improve the hydrolytic stability of the material and the adhesion of SMCs. A material with 5% polyethylene glycol, 90% PCL, and 5% pentaerythritol presented high cell viability and adhesion, suggesting a contractile phenotype in SMCs depending on the morphology. Nevertheless, all PUs retained their elastic modulus over 120 days, similar to the collagen of native arteries (similar to 10 MPa). Furthermore, aortic SMCs did not present toxicity (viability over 80%) and demonstrated adherence without any abnormal cell multiplication processes, which is ideal for the function to be fulfiled in situ in the vascular grafts.The research and publication were supported by the Universidad de La Sabana (ING-205-2018) and the Minister of Science, Technology, and Innovation of the Republic of Colombia, MINCIENCAS (Contract number 80740-186-2019). M. M-G. would like to thank the Universidad de La Sabana for the scholarship for her master's studies. S. A-A. would like to thank MINCIENCIAS for the doctoral training scholarship (Grant 727-2015). The authors are thankful to Professor Ericsson Coy Barrera and his staff at Nueva Granada Military University for the access to the VarioskanT LUX multimode microplate reader. J. A. S. acknowledges the financial support by MINECO through FIS2017-83295-P, MAT2015-71070-REDC, MAT2016-75586-C4-1/2/3-P and the Ramon y Cajal Fellowship (RYC-201517482). 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Study of the orpiment and anorpiment phases of As2S3 under pressure

[EN] In this work we study the pressure behaviour of the orpiment (monoclinic) and anorpiment (triclinic) layered structures of As2S3 by means of ab initio calculations performed within the density functional theory, as part of an ongoing theoretical and experimental joint effort to provide a comprehensive picture of the bonding of this interesting material and the evolution of its structural, electronic, and vibrational properties under pressure.The authors acknowledge the financial support from the Ministerio de Economia y Competitividad (MINECO) of Spain through Projects No. MAT2013-46649-C04-02-P and MAT2013-46649-C04-03-P. Computer time in the MALTA computer cluster at the University of Oviedo, Spain, is also gratefully acknowledged (MINECO Project No. CSD2007-00045).Randescu, S.; Mújica, A.; Rodríguez-Hernández, P.; Muñoz, A.; Ibañez, J.; Sans-Tresserras, JÁ.; Cuenca Gotor, VP.... (2017). Study of the orpiment and anorpiment phases of As2S3 under pressure. Journal of Physics: Conference Series. 950:042018-042018. https://doi.org/10.1088/1742-6596/950/4/042018S042018042018950Brazhkin, V. V., Katayama, Y., Kondrin, M. V., Lyapin, A. G., & Saitoh, H. (2010). Structural transformation yielding an unusual metallic state in liquidAs2S3under high pressure. Physical Review B, 82(14). doi:10.1103/physrevb.82.140202Gibbs, G. V., Wallace, A. F., Zallen, R., Downs, R. T., Ross, N. L., Cox, D. F., & Rosso, K. M. (2010). Bond Paths and van der Waals Interactions in Orpiment, As2S3. The Journal of Physical Chemistry A, 114(23), 6550-6557. doi:10.1021/jp102391aKampf, A. R., Downs, R. T., Housley, R. M., Jenkins, R. A., & Hyršl, J. (2011). Anorpiment, As2S3, the triclinic dimorph of orpiment. Mineralogical Magazine, 75(6), 2857-2867. doi:10.1180/minmag.2011.075.6.2857Bolotina, N. B., Brazhkin, V. V., Dyuzheva, T. I., Katayama, Y., Kulikova, L. F., Lityagina, L. V., & Nikolaev, N. A. (2014). High-pressure polymorphism of As2S3 and new AsS2 modification with layered structure. JETP Letters, 98(9), 539-543. doi:10.1134/s0021364013220025Bolotina, N. B., Brazhkin, V. V., Dyuzheva, T. I., Lityagina, L. M., Kulikova, L. F., Nikolaev, N. A., & Verin, I. A. (2013). Crystal structure of new AsS2 compound. Crystallography Reports, 58(1), 61-64. doi:10.1134/s1063774513010069Kresse, G., & Hafner, J. (1993). Ab initiomolecular dynamics for liquid metals. Physical Review B, 47(1), 558-561. doi:10.1103/physrevb.47.558Kresse, G., & Furthmüller, J. (1996). Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Computational Materials Science, 6(1), 15-50. doi:10.1016/0927-0256(96)00008-0Kresse, G., & Furthmüller, J. (1996). Efficient iterative schemes forab initiototal-energy calculations using a plane-wave basis set. Physical Review B, 54(16), 11169-11186. doi:10.1103/physrevb.54.11169Perdew, J. P., Burke, K., & Ernzerhof, M. (1996). Generalized Gradient Approximation Made Simple. Physical Review Letters, 77(18), 3865-3868. doi:10.1103/physrevlett.77.3865Perdew, J. P., Ruzsinszky, A., Csonka, G. I., Vydrov, O. A., Scuseria, G. E., Constantin, L. A., … Burke, K. (2008). Restoring the Density-Gradient Expansion for Exchange in Solids and Surfaces. Physical Review Letters, 100(13). doi:10.1103/physrevlett.100.136406Kresse, G., & Joubert, D. (1999). From ultrasoft pseudopotentials to the projector augmented-wave method. Physical Review B, 59(3), 1758-1775. doi:10.1103/physrevb.59.1758Blöchl, P. E. (1994). Projector augmented-wave method. Physical Review B, 50(24), 17953-17979. doi:10.1103/physrevb.50.17953Monkhorst, H. J., & Pack, J. D. (1976). Special points for Brillouin-zone integrations. Physical Review B, 13(12), 5188-5192. doi:10.1103/physrevb.13.5188Grimme, S. (2006). Semiempirical GGA-type density functional constructed with a long-range dispersion correction. Journal of Computational Chemistry, 27(15), 1787-1799. doi:10.1002/jcc.20495Grimme, S., Antony, J., Ehrlich, S., & Krieg, H. (2010). A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. The Journal of Chemical Physics, 132(15), 154104. doi:10.1063/1.3382344Birch, F. (1947). Finite Elastic Strain of Cubic Crystals. Physical Review, 71(11), 809-824. doi:10.1103/physrev.71.809Mujica, A., Rubio, A., Muñoz, A., & Needs, R. J. (2003). High-pressure phases of group-IV, III–V, and II–VI compounds. Reviews of Modern Physics, 75(3), 863-912. doi:10.1103/revmodphys.75.863Alfè, D. (2009). PHON: A program to calculate phonons using the small displacement method. Computer Physics Communications, 180(12), 2622-2633. doi:10.1016/j.cpc.2009.03.01

Project-based learning using scientific poster as a tool for learning and acquisition of skills in physics subjects of engineering bachelor’s degrees

This article shows the experience of working on project-based learning using scientific posters, on the study of the mass geometry of matter, with students of various Physics subjects of Degrees in Engineering of the School of Design Engineering of the Polytechnic University of Valencia. The development of this work has been carried out with a dual purpose: on the one hand, to improve the teachinglearning process of mass geometry; and, on the other hand, to improve the acquisition of skills by students. This matter, which is studied in the Physics subjects of the first year of the degree, forms part of the basis of the studies of resistance of materials and theory of mechanisms of subsequent courses. The inclusion of two sessions of laboratory practices, as an extension of the work carried out in the theory and classroom practice sessions, has allowed us to study more deeply the theoretical concepts of mass geometry and their application to a real project, improving the learning by the students. In addition, the presentation of the project through the scientific poster has facilitated the acquisition of cross-curricular competencies such as application and practical thinking, teamwork, effective communication, and critical thinking