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We report on Raman scattering measurements in mercury digallium selenide (HgGa2Se4) up to 25 GPa. We also performed, for the low-pressure defect-chalcopyrite structure, lattice-dynamics ab initio calculations at high pressures which agree with experiments. Measurements evidence that the semiconductor HgGa2Se4 exhibits a pressure-induced phase transition above 19 GPa to a previously undetected structure. This transition is followed by a transformation to a Raman-inactive phase above 23.4 GPa. On downstroke from 25 GPa until 2.5 GPa, a broad Raman spectrum was observed, which has been attributed to a fourth phase, and whose pressure dependence was followed during a second upstroke. Candidate structures for the three phases detected under compression are proposed. Finally, we also report and discuss the decomposition of the sample by laser heating at pressures close to 19 GPa. As possible products of decomposition, we have identified at least the formation of trigonal selenium nanoclusters and cinnabar-type HgSe. ; This study was supported by the Spanish government MEC under Grant No. MAT2010-21270-004-01/03/04, by MALTA Consolider Ingenio 2010 project (CSD2007-00045), by Generalitat Valenciana through project GVA-ACOMP-2013-012, and by the Vicerrectorado de Investigacion y Desarrollo of the Universidad Politecnica de Valencia (UPV2011-0966 and UPV2011-0914). E.P.-G., J.L.-S., A.M., and P.R.-H. acknowledge computing time provided by Red Espanola de Super-computacion (RES) and MALTA-Cluster. ; Vilaplana Cerda, RI.; Gomis Hilario, O.; Manjón Herrera, FJ.; Ortiz, HM.; Pérez González, E.; López Solano, J.; Rodríguez Hernández, P. (2013). Lattice dynamics study of HgGa2Se4 at high pressures. Journal of Physical Chemistry C. 117(30):15773-15781. https://doi.org/10.1021/jp402493r ; S ; 15773 ; 15781 ; 117 ; 30

15773 15781 117 30 ; S ; We report on Raman scattering measurements in mercury digallium selenide (HgGa2Se4) up to 25 GPa. We also performed, for the low-pressure defect-chalcopyrite structure, lattice-dynamics ab initio calculations at high pressures which agree with experiments. Measurements evidence that the semiconductor HgGa2Se4 exhibits a pressure-induced phase transition above 19 GPa to a previously undetected structure. This transition is followed by a transformation to a Raman-inactive phase above 23.4 GPa. On downstroke from 25 GPa until 2.5 GPa, a broad Raman spectrum was observed, which has been attributed to a fourth phase, and whose pressure dependence was followed during a second upstroke. Candidate structures for the three phases detected under compression are proposed. Finally, we also report and discuss the decomposition of the sample by laser heating at pressures close to 19 GPa. As possible products of decomposition, we have identified at least the formation of trigonal selenium nanoclusters and cinnabar-type HgSe. This study was supported by the Spanish government MEC under Grant No. MAT2010-21270-004-01/03/04, by MALTA Consolider Ingenio 2010 project (CSD2007-00045), by Generalitat Valenciana through project GVA-ACOMP-2013-012, and by the Vicerrectorado de Investigacion y Desarrollo of the Universidad Politecnica de Valencia (UPV2011-0966 and UPV2011-0914). E.P.-G., J.L.-S., A.M., and P.R.-H. acknowledge computing time provided by Red Espanola de Super-computacion (RES) and MALTA-Cluster. Vilaplana Cerda, RI.; Gomis Hilario, O.; Manjón Herrera, FJ.; Ortiz, HM.; Pérez González, E.; López Solano, J.; Rodríguez Hernández, P. (2013). Lattice dynamics study of HgGa2Se4 at high pressures. Journal of Physical Chemistry C. 117(30):15773-15781. https://doi.org/10.1021/jp402493r

We report on high-pressure x-ray diffraction measurements up to 17.2 GPa in mercury digallium selenide (HgGa2Se4). The equation of state and the axial compressibilities for the low-pressure tetragonal phase have been determined and compared to related compounds. HgGa2Se4 exhibits a phase transition on upstroke toward a disordered rock-salt structure beyond 17 GPa, while on downstroke it undergoes a phase transition below 2.1 GPa to a phase that could be assigned to a metastable zinc-blende structure with a total cation-vacancy disorder. Thermal annealing at low- and high-pressure shows that kinetics plays an important role on pressure-driven transitions. ; This study was supported by the Spanish government MEC under grants nos: MAT2010-21270-C04-01/03/04 and CTQ2009-14596-C02-01, by the Comunidad de Madrid and European Social Fund (S2009/PPQ-1551 4161893), 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., 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, F.; Santamaría Pérez, D.; Errandonea, D.; Pérez González, E.; López Solano, J. (2013). Crystal structure of HgGa2Se4 under compression. Materials Research Bulletin. 48:2128-2133. https://doi.org/10.1016/j.materresbull.2013.02.037 ; S ; 2128 ; 2133 ; 48

135181 1351815 111 1 ; S Krämer, 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.1984.169.1-4.283 ; 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 Physics This 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 ...

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 Physics ; This 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/10.1063/1.3675162 ; S ; 135181 ; 1351815 ; 111 ; 1 ; A. MacKinnon, in Tables of Numerical Data and Functional ...

Póster elaborado para el Quadrennial Ozone Symposium celebrado en Edimburgo del 4 al 9 de septiembre de 2016. ; This work has been supported by the European Metrology Research Programme (EMRP) within the joint research project ENV59 "Traceability for atmospheric total column ozone" (ATMOZ). The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union.

From 25 May to 5 June 2015, the 10th regional intercomparison campaign of the Regional Brewer Calibration Center – Europe (RBCC-E) was held at El Arenosillo atmospheric sounding station of the Instituto Nacional de Técnica Aeroespacial (INTA). This campaign was jointly conducted by COST Action ES1207 EUBREWNET and the Area of Instrumentation and Atmospheric Research of INTA. A total of 21 Brewers, 11 single- and 10 double-monochromator instruments from 11 countries participated and were calibrated for total column ozone (TOC) and solar UV irradiance. In this 2015 campaign we have introduced a formal approach to the characterisation of the internal instrumental stray light, the filter non-linearity and the algorithm for correcting for its effects on the TOC calculations. This work shows a general overview of the ozone comparison and the evaluation of the correction of the spectral stray light effect for the single-monochromator Brewer spectrophotometer, derived from the comparison with a reference double-monochromator Brewer instrument. At the beginning of the campaign, 16 out of the 21 participating Brewer instruments agreed within better than ±1%, and 10 instruments agreed within better than ±0.5% considering data with ozone slant column between 100 and 900DU, which does not require instrumental stray light correction. ; This article is based upon work from COST Action 1207 EUBREWNET. This work has been supported by the European Metrology Research Programme within the joint research project ENV59 "Traceability for atmospheric total column ozone" (ATMOZ). The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union. We also gratefully acknowledge further support by the Fundación General de la Universidad de La Laguna. This study and the campaigns were supported at large part by ESA project CEOS Intercalibration of ground-pectrometers and lidars (ESRIN contract 22202/09/I-EC).

Póster presentado en: 9th International Workshop on Sand/Duststorms and Associated Dustfall, celebrado en Tenerife del 22 al 24 de mayo de 2018. ; This work has been performed within the framework of COST Action ES1207 "The European Brewer Network" (EUBREWNET), supported by COST (European Cooperation in Science and Technology). Part of this work has been developed within the IDEAS+ project of the European Space Agency, in collaboration with LuftBlick Earth Observation Technologies. This work has been supported by the European Metrology Research Programme (EMRP) within the joint research project ENV59 "Traceability for atmospheric total column ozone" (ATMOZ). The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union. These activities have been partially developed in the WMO-CIMO Testbed for Aerosols and Water Vapor Remote Sensing Instruments (Izaña, Spain). We also acknowledge the support of the Ministry of Economy and Competitiveness of Spain and the European Regional Development Fund (ERDF) under the POLARMOON (CTM2015-66742-R) and AEROATLAN (CGL2015-66299-P) projects. Stratospheric ozone and spectral UV baseline monitoring in the United Kingdom is supported by DEFRA, The Department for the Environment, Food, and Rural Affairs, since 2003. Some of the AERONET sun photometers used in this work have been calibrated within the AERONET Europe TNA, supported by the European Community-Research Infrastructure Action under the Horizon 2020 research and innovation program, ACTRIS-2 grant agreement No. 654109. We gratefully the acknowledge the PIs of the Madrid, Izaña, and Tamanrasset AERONET stations.