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690 697 27 3 ; S ; [EN] In Physics, many quantities are vectors, and their use requires typical operations such as addition, subtraction, scalar multiplication, scalar product (dot product), vector product (cross product), and scalar triple product. This is a very basic topic in all General Physics courses for Engineering degrees. However, we have detected that some students lack a deep understanding of vector operations and their properties. In this study, we present a virtual laboratory (developed using the tool Easy Java Simulations) for the study and understanding of these topics. The user can introduce the components of the input vectors and gets a three-dimensional representation, which can be scaled and rotated for better visualization. Any of the aforementioned operations can be selected, and the result is shown both numerically and graphically. The user can also modify any represented vector. In this way, the virtual lab provides a real-time visualization of how the change affects the result. The possibility of limiting the changes to either magnitude or direction is also included. The efficiency of the virtual laboratory has been tested analyzing the results obtained in two groups of students (virtual laboratory vs traditional resources). A satisfaction survey has been also carried out. Salinas Marín, I.; Gimenez Valentin, MH.; Cuenca Gotor, VP.; Seiz Ortiz, R.; Monsoriu Serra, JA. (2019). Design and evaluation of a three-dimensional virtual laboratory on vector operations. Computer Applications in Engineering Education. 27(3):690-697. https://doi.org/10.1002/cae.22108 Vidaurre, A., Riera, J., Giménez, M. H., & Monsoriu, J. A. (2002). Contribution of digital simulation in visualizing physics processes. Computer Applications in Engineering Education, 10(1), 45-49. doi:10.1002/cae.10016 Depcik, C., & Assanis, D. N. (2005). Graphical user interfaces in an engineering educational environment. Computer Applications in Engineering Education, 13(1), 48-59. doi:10.1002/cae.20029 Jimoyiannis, A., & ...

[EN] We report a joint experimental and theoretical study of the structural, vibrational, and electronic properties of layered monoclinic arsenic sulfide crystals (a-As2S3), aka mineral orpiment, under compression. X-ray diffraction and Raman scattering measurements performed on orpiment samples at high pressure and combined with ab initio calculations have allowed us to determine the equation of state and the tentative assignment of the symmetry of many Raman-active modes of orpiment. From our results, we conclude that no first-order phase transition occurs up to 25 GPa at room temperature; however, compression leads to an isostructural phase transition above 20 GPa. In fact, the As coordination increases from threefold at room pressure to more than fivefold above 20 GPa. This increase in coordination can be understood as the transformation from a solid with covalent bonding to a solid with metavalent bonding at high pressure, which results in a progressive decrease of the electronic and optical bandgap, an increase of the dielectric tensor components and Born effective charges, and a considerable softening of many high-frequency optical modes with increasing pressure. Moreover, we propose that the formation of metavalent bonding at high pressures may also explain the behavior of other group-15 sesquichalcogenides under compression. In fact, our results suggest that group-15 sesquichalcogenides either show metavalent bonding at room pressure or undergo a transition from p-type covalent bonding at room pressure towards metavalent bonding at high pressure, as a precursor towards metallic bonding at very high pressure. ; The authors are thankful for the financial support from Spanish Ministerio de Economia y Competitividad (MINECO) through MAT2016-75586-C4-2/3-P, FIS2017-83295-P and MALTA Consolider Team project (RED2018-102612-T). Also from Generalitat Valenciana under project PROMETEO/2018/123-EFIMAT. ELDS acknowledges the European Union FP7 People: Marie-Curie Actions programme for grant agreement No. ...

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.jpcc.6b06049 ; We report a study of the structural, vibrational, and electronic properties of layered monoclinic arsenic telluride (α-As2Te3) at high pressures. Powder X-ray diffraction and Raman scattering measurements up to 17 GPa have been complemented with ab initio total-energy, lattice dynamics, and electronic band structure calculations. Our measurements, which include previously unreported Raman scattering measurements for crystalline α-As2Te3, show that this compound undergoes a reversible phase transition above 14 GPa at room temperature. The monoclinic crystalline structure of α-As2Te3 and its behavior under compression are analyzed by means of the compressibility tensor. Major structural and vibrational changes are observed in the range between 2 and 4 GPa and can be ascribed to the strengthening of interlayer bonds. No evidence of any isostructural phase transition has been observed in α-As2Te3. A comparison with other group 15 sesquichalcogenides allows understanding the structure of α-As2Te3 and its behavior under compression based on the activity of the cation lone electron pair in these compounds. Finally, our electronic band structure calculations show that α-As2Te3 is a semiconductor at 1 atm, which undergoes a trivial semiconducting−metal transition above 4 GPa. The absence of a pressure-induced electronic topological transition in α-As2Te3 is discussed. ; This work has been performed under financial support from Projects MAT2013-46649-C4-2-P, MAT2013-46649-C4-3-P, MAT2015-71070-REDC, FIS2013-48286-C2-1-P, and FIS2013-48286-C2-2-P of the Spanish Ministry of Economy and Competitiveness (MINECO), and the Department of Education, Universities and Research of the Basque Government and UPV/EHU ...