Primeros datos arqueométricos sobre la metalurgia del poblado y necrópolis de Calvari del Molar (Priorat, Tarragona)

La presencia de materiales fenicios en el curso del río Ebro se ha relacionado con su interés hacia los recursos mineros del nordeste peninsular en general y del área Molar-Bellmunt-Falset en particular, pero hasta la fecha esta propuesta no había sido adecuadamente contrastada. En este artículo presentamos las primeras evidencias de actividad metalúrgica procedentes del poblado de Calvari del Molar (Priorat, Tarragona) (campañas 2002-2003), que consisten en una tobera de tipología desconocida hasta la fecha en Cataluña, un molino empleado para triturar el mineral y una punta de flecha orientalizante que puede interpretarse como una imitación local de modelos foráneos. Damos a conocer también el estudio arqueometalúrgico de otros cuatro bronces procedentes de las excavaciones de S. Vilaseca (1930). La publicación de los resultados arqueológicos y arqueomé- tricos nos sirve para presentar las perspectivas de futuro de nuestra investigación acerca del poblado, de su área minero-metalúrgica y de su relación con los intereses comerciales fenicios. Se presta especial atención a la plata, obtenida a partir de minerales de este metal, plata nativa y galena argentífera, como un subproducto de la explotación de plomo

Structural, vibrational and electronic properties of alpha'-Ga2S3 under compression

[EN] We report a joint experimental and theoretical study of the low-pressure phase of ¿¿-Ga2S3 under compression. Theoretical ab initio calculations have been compared to X-ray diffraction and Raman scattering measurements under high pressure carried out up to 17.5 and 16.1 GPa, respectively. In addition, we report Raman scattering measurements of ¿¿-Ga2S3 at high temperature that have allowed us to study its anharmonic properties. To understand better the compression of this compound, we have evaluated the topological properties of the electron density, the electron localization function, and the electronic properties as a function of pressure. As a result, we shed light on the role of the Ga¿S bonds, the van der Waals interactions inside the channels of the crystalline structure, and the single and double lone electron pairs of the sulphur atoms in the anisotropic compression of ¿¿-Ga2S3. We found that the structural channels are responsible for the anisotropic properties of ¿¿-Ga2S3 and the A¿(6) phonon, known as the breathing mode and associated with these channels, exhibits the highest anharmonic behaviour. Finally, we report calculations of the electronic band structure of ¿¿-Ga2S3 at different pressures and find a nonlinear pressure behaviour of the direct band gap and a pressure-induced direct-to-indirect band gap crossover that is similar to the behaviour previously reported in other ordered-vacancy compounds, including ß-Ga2Se3. The importance of the single and, more specially, the double lone electron pairs of sulphur in the pressure dependence of the topmost valence band of ¿¿-Ga2S3 is stressed.The authors thank the financial support from the Spanish Research Agency (AEI) under projects MALTA Consolider Team network (RED2018-102612-T) and projects MAT2016-75586-C4-2/3-P, FIS2017-83295-P, PID2019-106383GB-42/43, and PGC2018-097520-A-100, as well as from Generalitat Valenciana under Project PROMETEO/2018/123 (EFIMAT). A. M. and P. R.-H. acknowledge computing time provided by Red Espanola de Supercomputacion (RES) and MALTA-Cluster and E. L. D. S. acknowledges Marie Sklodowska-Curie Grant No. 785789-COMEX from the European Union's Horizon 2020 research and innovation program. J. A. S. also wants to thank the Ramon y Cajal fellowship (RYC-2015-17482) for financial support. We also thank the ALBA synchrotron light source for funded experiment 2017022088 at the MSPD-BL04 beamline.Gallego-Parra, S.; Vilaplana Cerda, RI.; Gomis, O.; Lora Da Silva, E.; Otero-De-La-Roza, A.; Rodríguez-Hernández, P.; Muñoz, A.... (2021). Structural, vibrational and electronic properties of alpha'-Ga2S3 under compression. Physical Chemistry Chemical Physics. 23(11):6841-6862. https://doi.org/10.1039/d0cp06417cS68416862231

Pressure-induced phase transition and band-gap collapse in the wide-band-gap semiconductor InTaO4

A pressure-induced phase transition, associated with an increase of the coordination number of In and Ta, is detected beyond 13 GPa in InTaO4 by combining synchrotron x-ray diffraction and Raman measurements in a diamond-anvil cell with ab initio calculations. High-pressure optical-absorption measurements were also carried out. The high-pressure phase has a monoclinic structure that shares the same space group with the low-pressure phase (P2/c). The structure of the high-pressure phase can be considered as a slight distortion of an orthorhombic structure described by space group Pcna. The phase transition occurs together with a unit-cell volume collapse and an electronic band-gap collapse observed by experiments and calculations. Additionally, a band crossing is found to occur in the low-pressure phase near 7 GPa. The pressure dependence of all the Raman-active modes is reported for both phases as well as the pressure dependence of unit-cell parameters and the equations of state. Calculations also provide information on infrared-active phonons and bond distances. These findings provide insights into the effects of pressure on the physical properties of InTaO4.This paper was partially supported by the Spanish Ministerio de Economia y Competitividad (MINECO) under Grants No. MAT2013-46649-C04-01/02/03 and No. MAT2015-71070-REDC (MALTA Consolider). The XRD experiments were performed at the MSPD-BL04 beamline at ALBA Synchrotron with the collaboration of ALBA staff. We thank S. Agouram from SC-SIE at Universitat de Valencia for technical support with the transmission electron microscope measurements.Errandonea, D.; Popescu, C.; Garg, A.; Botella, P.; Martinez García, D.; Pellicer Porres, J.; Rodríguez Hernández, P.... (2016). Pressure-induced phase transition and band-gap collapse in the wide-band-gap semiconductor InTaO4. 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Characterization and Decomposition of the Natural van der Waals SnSb2Te4 under Compression

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Inorganic Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.inorgchem.0c01086.[EN] High pressure X-ray diffraction, Raman scattering, and electrical measurements, together with theoretical calculations, which include the analysis of the topological electron density and electronic localization function, evidence the presence of an isostructural phase transition around 2 GPa, a Fermi resonance around 3.5 GPa, and a pressure-induced decomposition of SnSb2Te4 into the high-pressure phases of its parent binary compounds (alpha-Sb2Te3 and SnTe) above 7 GPa. The internal polyhedral compressibility, the behavior of the Raman-active modes, the electrical behavior, and the nature of its different bonds under compression have been discussed and compared with their parent binary compounds and with related ternary materials. In this context, the Raman spectrum of SnSb2Te4 exhibits vibrational modes that are associated but forbidden in rocksalt-type SnTe; thus showing a novel way to experimentally observe the forbidden vibrational modes of some compounds. Here, some of the bonds are identified with metavalent bonding, which were already observed in their parent binary compounds. The behavior of SnSb2Te4 is framed within the extended orbital radii map of BA(2)Te(4) compounds, so our results pave the way to understand the pressure behavior and stability ranges of other "natural van der Waals" compounds with similar stoichiometry.This work has been performed under financial support from the Spanish MINECO under Project MALTA-CONSOLIDER TEAM network (RED2018-102612-T) and Project FIS2017-83295-P, from Generalitat Valenciana under Project PROMETEO/2018/123. This publication is a product of the "Programa de Valoracion y Recursos Conjuntos de I+D+i VLC/CAMPUS and has been financed by the Spanish Ministerio de Educacion, Cultura y Deporte, as part of "Programa Campus de Excelencia Internacional". Supercomputer time has been provided by the Red Espanola de Supercomputacion (RES) and the MALTA cluster. J.A.S. acknowledges a "Ramon y Cajal" fellowship (RYC-2015-17482) for financial support, and E.L.D.S. acknowledges Marie Sklodowska-Curie Grant No. 785789-COMEX from the European Union's Horizon 2020 research and innovation program. We also thank ALBA synchrotron and DIAMOND light source for funded experiments.Sans-Tresserras, JÁ.; Vilaplana Cerda, RI.; Da Silva, EL.; Popescu, C.; Cuenca-Gotor, VP.; Andrada-Chacón, A.; Sánchez-Benitez, J.... (2020). Characterization and Decomposition of the Natural van der Waals SnSb2Te4 under Compression. Inorganic Chemistry. 59(14):9900-9918. https://doi.org/10.1021/acs.inorgchem.0c01086S990099185914Mellnik, A. R., Lee, J. S., Richardella, A., Grab, J. L., Mintun, P. J., Fischer, M. H., … Ralph, D. C. (2014). Spin-transfer torque generated by a topological insulator. Nature, 511(7510), 449-451. doi:10.1038/nature13534Chen, Y. L., Analytis, J. G., Chu, J.-H., Liu, Z. K., Mo, S.-K., Qi, X. L., … Shen, Z.-X. (2009). 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beta-Bi2O3 under compression: Optical and elastic properties and electron density topology analysis

We report a joint experimental and theoretical study of the optical properties of tetragonal bismuth oxide (beta-Bi2O3) at high pressure by means of optical absorption measurements combined with ab initio electronic band structure calculations. Our results are consistent with previous results that show the presence of a second-order isostructural phase transition in Bi2O3 (from beta to beta') around 2 GPa and a phase transition above 15 GPa combined with a pressure-induced amorphization above 17-20 GPa. In order to further understand the pressure-induced phase transitions and amorphization occurring in beta-Bi2O3, we theoretically studied the mechanical and dynamical stability of the tetragonal structures of beta- and beta'-Bi2O3 at high pressure through calculations of their elastic constants, elastic stiffness coefficients, and phonon dispersion curves. The pressure dependence of the elastic stiffness coefficients and phonon dispersion curves confirms that the isostructural phase transition near 2 GPa is of ferroelastic nature. Furthermore, a topological study of the electron density shows that the ferroelastic transition is not caused by a change in number of critical points (cusp catastrophe), but by the equalization of the electron densities of both independent O atoms in the unit cell due to a local rise in symmetry. Finally, from theoretical simulations, beta'-Bi2O3 is found to be mechanically and dynamically stable at least up to 26.7 GPa under hydrostatic conditions; thus, the pressure-induced amorphization reported above 17-20 GPa in powder beta'-Bi2O3 using methanol-ethanol-water as pressure-transmitting medium could be related to the frustration of a reconstructive phase transition at room temperature and the presence of mechanical or dynamical instabilities under nonhydrostatic conditions.This work was performed with financial support from the Spanish Ministerio de Economia y Competitividad under Projects No. MAT2013-46649-C4-2/3-P and No. MAT2015-71070-REDC. This publication is the fruit of "Programa de Valoracion y Recursos Conjuntos de I+D+i VLC/CAMPUS" and was financed by the Spanish Ministerio de Educacion, Cultura y Deporte as part of "Programa Campus de Excelencia Internacional" through Projects No. SP20140701 and No. SP20140871 and by the Brazilian Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) under Project No. 201050/2012-9. Supercomputer time was provided by the Red Espanola de Supercomputacion (RES) and the MALTA cluster. J.A.S. acknowledges financial support through the Juan de la Cierva fellowship (JCI-2011-09781).Pereira, ALJ.; Gomis, O.; Sans Tresserras, JÁ.; Contreras-García, J.; Manjón Herrera, FJ.; Rodríguez-Hernández, P.; Muñoz, A.... (2016). beta-Bi2O3 under compression: Optical and elastic properties and electron density topology analysis. Physical review B: Condensed matter and materials physics. 93(22):224111-1-224111-13. https://doi.org/10.1103/PhysRevB.93.224111S224111-1224111-13932

Structural and vibrational behavior of cubic Cu1.80(3)Se cuprous selenide, berzelianite, under compression

[EN] We have performed an experimental study of the crystal structure and lattice dynamics of cubic Cu1.80(3)Se at ambient temperature and high pressures. Two reversible phase transitions were found at 2.9 and 8.7 GPa. The indexation of the angle-dispersive synchrotron x-ray diffraction patterns suggests a large orthorhombic cell and a monoclinic cell for the high-pressure phases. Raman measurements provide additional information on the local structure. The compressibility of the three ambient temperature phases has been determined and compared to that of other sulphides and selenides.This work has been performed under financial support from Spanish MICINN under projects MAT2016-75586-C4-2/3-P, FIS2017-83295-P, and PGC2018-097520-A-I00, as well as under the MALTA Consolider Team network (RED2018-102612-T), from Generalitat Valenciana under project PROMETEO/2018/123-EFIMAT, and from Brazilian Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) under projects 307199/2018-5, 422250/2016-3, and 201050/2012-9. D.S-P. and J.A.S. acknowledge the financial support of the Spanish MINECO for the RyC-2014-15643 and RyC-2015-17482 Ramon y Cajal Grants, respectively. We also thank ALBA synchrotron for funded experiment No. 2012010266.Chulia-Jordan, R.; Santamaria-Perez, D.; Pereira, ALJ.; Garcia-Domene, B.; Vilaplana Cerda, RI.; Sans-Tresserras, JÁ.; Martinez-Garcia, D.... (2020). Structural and vibrational behavior of cubic Cu1.80(3)Se cuprous selenide, berzelianite, under compression. Journal of Alloys and Compounds. 830:154646 - 1-154646 - 8. https://doi.org/10.1016/j.jallcom.2020.154646S154646 - 1154646 - 883