Computer simulation of ionic solids of technological interest

In the present study we have applied Quantum Mechanical (QM) and Molecular Mechanics (MM) computational methods to solid state materials of interest, specifically: metal hydrides, olivines, ceria and tin oxide crystals. A new empirical potential set has been derived for the following metal hydrides; NaH, LiH, MgH2, CaH2 and BaH2. Studies of atomic diffusion have been performed in LiH and CaH2 and agree well with the available experimental data. MM simulations of cation diffusion in olivines have been performed. Diffusion has been found to come mainly from Mi-Mi nearest neighbour jumps with a smaller contribution by site exchange, MrM2 and M2-M1; jumps. The spatial exploration of non-linear diffusion paths has been shown crucial in order to yield correct estimations of the activation energy of diffusion. MM calculations of solution and clustering of Cu2+ in ceria show that, on the contrary to previous work, it is quite likely that the dopant enters in interstitials sites and, consequently all clusters observed experimentally may be formed by Cu2+ interstitials. QM cluster and periodic slab simulations have been performed on the CO and C02 adsorption on the (110) perfect surface of Sn02 with HF and DFT methods. These calculations show that, for CO, the molecule adsorbs on pentacoordinated cations on, ideal, truncated bulk, and relaxed surfaces. The interaction with the surface is mostly electrostatic and well described by uncorrelated methods. In the C02 case, the molecule adsorbs perpendicularly to the surface on the same site, but the main bonding contribution is the polarization of the C02 and DFT methods are necessary to properly describe the binding. Carbonates have been shown to be formed only as metastable species on the perfect (100) Sn02 surface

Planar and Helical Dinaphthophenazines

[EN] In this study, we report the synthesis of a series of planar and helical dinaphthophenazines by cyclocondensation reactions between the newly developed 9,10-bis((triisopropylsilyl)ethynyl)-anthracene-1,2-dione and different diamines. Their optoelectronic and electrochemical properties are studied by ultraviolet-visible (UV-vis) spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and density functional theory calculations.A.M.-A. acknowledges support of the Basque Foundation for Science (Ikerbasque), POLYMAT, the University of the Basque Country, Diputacion Foral de Guipuzcoa, Gobierno Vasco (BERC programme) and Gobierno de Espana (Project CEX2020-001067-M financed by MCIN/AEI/10.13039/501100011033). Technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF) is acknowledged. This project received funding from the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Programme (grant agreement no. 722951). This project received funding from the European Union's Horizon 2020 Research and Innovation Programme under grant agreement nos. 664878 and 899895. F.C. and A.M.-A acknowledge that this project received funding from the European Union's Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie grant agreement no. 839626. M.M.-F. acknowledges support from the Portuguese Foundation for Science and Technology (FCT), under the project IF/00894/2015, and the project CICECO-Aveiro Institute of Materials, FCT ref UID/CTM/50011/2019, UIDB/50011/2020, and UIDP/50011/2020, financed by national funds through the FCT/MEC and when appropriate c-financed by FEDER under the PT2020 Partnership Agreement

Inducing Single-Handed Helicity in a Twisted Molecular Nanoribbon

[EN] Molecular conformation has an important role in chemistry and materials science. Molecular nanoribbons can adopt chiral twisted helical conformations. However, the synthesis of single-handed helically twisted molecular nanoribbons still represents a considerable challenge. Herein, we describe an asymmetric approach to induce single-handed helicity with an excellent degree of conformational discrimination. The chiral induction is the result of the chiral strain generated by fusing two oversized chiral rings and of the propagation of that strain along the nanoribbon's backbone.This work was carried out with support from the Basque Science Foundation for Science (Ikerbasque), POLYMAT, the University of the Basque Country, Gobierno Vasco (BERC Programme) and Gobierno de Espana (Ministerio de Ciencia e Innovacion, Plan Estatal de Investigacion Cientifica y Tecnica y de Innovacion). Technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF) is acknowledged. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant Agreement No. 722951). This project has received funding from the European Union's Horizon 2020 research and innovation programme under Grant Agreement No. 899895. In addition, support through the project IF/00894/2015, the advanced computing project CPCA/A2/2524/2020 granting access to the Navigator cluster at LCA-UC and within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 and UIDP/50011/2020 funded by national funds through the Portuguese Foundation for Science and Technology I.P./MCTES is gratefully acknowledged

Doubling the Length of the Longest Pyrene-Pyrazinoquinoxaline Molecular Nanoribbons

[EN] Molecular nanoribbons are a class of atomically-precise nanomaterials for a broad range of applications. An iterative approach that allows doubling the length of the longest pyrene-pyrazinoquinoxaline molecular nanoribbons is described. The largest nanoribbon obtained through this approach-with a 60 linearly-fused ring backbone (14.9 nm) and a 324-atoms core (C276N48)-shows an extremely high molar absorptivity (values up to 1 198 074 M-1 cm(-1)) that also endows it with a high molar fluorescence brightness (8700 M-1 cm(-1)).This work was carried out with support from the Basque Science Foundation for Science (Ikerbasque), POLYMAT, the University of the Basque Country, Diputacion de Guipuzcoa, Gobierno Vasco (BERC programme) and Gobierno de Espana (Project CEX2020-001067-M financed by MCIN/AEI/10.13039/501100011033). Technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF) is acknowledged. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant Agreement No. 722951). This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 899895. In addition, support through the project IF/00894/2015, the advanced computing project CPCA/A2/2524/2020 granting access to the Navigator cluster at LCA-UC and within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020 funded by national funds through the Portuguese Foundation for Science and Technology I.P./MCTES is gratefully acknowledged

Modulating Strain in Twisted Pyrene-Fused Azaacenes

The design and synthesis of strained aromatics provide an additional insight into the relationship between structure and properties. In the last years, several approaches to twist pyrene-fused azaacenes have been developed that allow to introduce twists of different sizes. Herein, we describe the synthesis of a new set of twisted dibenzotetraazahexacenes constituted by fused pyrene and quinoxaline residues that have been distorted by introducing increasingly larger substituents on the quinoxaline residues. Their twisted structure has been demonstrated by single-crystal X-ray diffraction. Furthermore, absorption, fluorescence, electrochemical and theoretical studies shine light on the effects of the substituents and twists on the optoelectronic and redox properties.This work was carried out with support from the Basque Science Foundation for Science (Ikerbasque), POLYMAT, the University of the Basque Country, Diputación de Guipúzcoa, Gobierno Vasco (PIBA_2022_1_0031 and BERC programme) and Gobierno de España (Projects PID2021-124484OB-I00 and CEX2020-001067-M financed by MCIN/AEI/10.13039/501100011033). Project (PCI2022-132921) funded by the Agencia Estatal de Investigación through the PCI 2022 and M-ERA.NET 2021 calls. This project has received funding from the European Research Council (ERC) under the European Union's Horizon2020 research and innovation programme (Grant Agreement No. 722951). This work was funded by the European Union under the Horizon Europe grant 101046231. Technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF) is acknowledged. In addition, support through the project IF/00894/2015, the advanced computing project 2021.09622.CPCA granting access to the Navigator cluster at LCA-UC, and within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MEC (PIDDAC) is gratefully acknowledged

A Thiadiazole-capped Nanoribbon with 18 Linearly-Fused Rings

Polycyclic aromatic hydrocarbons that extend over 2 nm in one dimension are seen as monodisperse graphene nanoribbons, which have attracted significant attention for a broad range of applications in organic electronics and photonics. Herein we report the synthesis of a stable bisthiadiazole-capped pyrene-containing nanoribbon with 18 linearly fused rings (NR-18-TD). Thanks to the presence of alternating tert-butyl and tri-iso-butylsilyl groups, NR-18-TD is highly soluble in organic solvents and therefore its structure and fundamental optoelectronic, redox and electrical properties could be unambiguously established. This work illustrates that NR-18-TD is a promising soluble NR-based n-type semiconductor for applications in organic electronics.The authors are grateful to the Basque Science Foundation for Science (Ikerbasque), POLYMAT, the University of the Basque Country (Grupo de Investigación GIU17/054 and SGIker), Gobierno de España (Ministerio de Economía y Competitividad CTQ2016-77970-R and CTQ2015-71936-REDT), Gobierno Vasco (BERC program), CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT ref. UID/CTM/50011/2013), Diputación Foral de Guipúzcoa (OF215/2016(ES)) and the FP7 framework program of the European Union (Marie Curie Career Integration Grant No. 618247 (NIRVANA)). This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 664878. This project has also received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 722951

A Sterically Congested Nitrogenated Benzodipentaphene with a Double π-Expanded Helicene Structure

Herein, we describe a series of three sterically congested nitrogenated benzodipentaphenes, one of which shows a highly distorted aromatic backbone with an unprecedented double π-expanded helicene structure.A.M.-A. acknowledge support of the Basque Science Foundation for Science (Ikerbasque), POLYMAT, the University of the Basque Country (Grupo de Investigación No. GIU17/054), Gobierno Vasco (No. PIBA 2019-09 and BERC program), and Gobierno de España (Ministerio de Economı́a y Competitividad No. CTQ2016-77970-R) and thank for technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF). F.C. and A.M.-A acknowledge that this project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme, under the Marie Skłodowska-Curie Grant Agreement No. 839626. A.M.-A. acknowledge that this project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme (Grant Agreement No. 722951). A.S. acknowledges the support of Japan Society for the Promotion of Science (JSPS) with the KAKENHI Grant-in-Aid for Scientific Research (A) (Grant No. JP16H02285). M.M.-F. acknowledges support from the Portuguese Foundation for Science and Technology (FCT), under the project IF/00894/2015, and the project CICECO-Aveiro Institute of Materials, FCT ref. UID/CTM/50011/2019, UIDB/50011/2020, and UIDP/50011/2020, financed by national funds through the FCT/MEC and, when appropriate, cofinanced by FEDER, under the PT2020 Partnership Agreement

Two high-performance alternatives to ZLIB scientific-data compression

ZLIB is used in diverse frameworks by the scientific community, both to reduce disk storage and to alleviate pressure on I/O. As it becomes a bottleneck on multi-core systems, higher throughput alternatives must be considered, exploring parallelism and/or more effective compression schemes. This work provides a comparative study of the ZLIB, LZ4 and FPC compressors (serial and parallel implementations), focusing on CR, bandwidth and speedup. LZ4 provides very high throughput (decompressing over 1GB/s versus 120MB/s for ZLIB) but its CR suffers a degradation of 5-10%. FPC also provides higher throughputs than ZLIB, but the CR varies a lot with the data. ZLIB and LZ4 can achieve almost linear speedups for some datasets, while current implementation of parallel FPC provides little if any performance gain. For the ROOT dataset, LZ4 was found to provide higher CR, scalability and lower memory consumption than FPC, thus emerging as a better alternative to ZLIB.This work is funded by National Funds through the FCT Fundacao para a Ciencia e a Tecnologia (Portuguese Foundation for Science and Technology) within project PEst-OE/EEI/UI0752/2014, UT Austin - Portugal FCT grant SFRH/ BD/47840/2008, and the resources from the project SeARCH funded under contract CONC- REEQ/443/2005. We would also like to thank Nuno Castro and Rafael Silva for their contributions

Towards understanding the active sites for the ORR in N-doped carbon materials through fine-tuning of nitrogen functionalities: an experimental and computational approach

The design of advanced N-doped carbon materials towards oxygen reduction reaction (ORR) catalysis is only possible if the nature of the active sites is fully understood. There is an important piece of research seeking to overcome this challenge through experimental or theoretical results. However, the combination of both approaches is necessary to deepen the knowledge about this subject. This work presents excellent agreement between experimental results and computational models, which provides evidence of the nature of the most active sites in N-doped carbon materials. N-doped carbon materials have been experimentally obtained through double stage treatment of polyaniline in distinct atmospheres (both oxygen-containing and inert atmospheres) at different temperatures (800–1200 °C). According to temperature programmed desorption (TPD), Raman spectroscopy, N2-adsorption isotherms at −196 °C and X-ray photoelectron spectroscopy (XPS), this synthesis method results in the selective formation of nitrogen species, without significant changes in structural order or porosity. ORR catalytic tests evidence the highly efficient catalysis, with platinum-like performance in terms of the current density and onset potential, of N-doped carbon materials selectively containing graphitic-type nitrogen species. Computational chemistry, through DFT calculations, shows that edge-type graphitic nitrogen is more effective towards ORR catalysis than pyridinic, pyrrolic, pyridonic, oxidized and basal-type graphitic nitrogen species.The authors thank Ministerio de Ciencia, Innovación y Universidades and FEDER for financial support (Project RTI2018-095291-B-I00, ENE2017-90932-REDT and FIS2015-64222-C2-2-P). MMF acknowledges support from the Portuguese Foundation for Science and Technology (FCT), under the projects IF/00894/2015, and FCT Ref. UID/CTM/50011/2019 for CICECO - Aveiro Institute of Materials

Thermoelectric properties of polypropylene carbon nanofiber melt-mixed composites: exploring the role of polymer on their Seebeck coefficient

The effect of polypropylene (PP) on the Seebeck coefficient (S) of carbon nanofibers (CNFs) in melt-extruded PP composites filled with up to 5 wt. % of CNFs was analyzed in this study. The as-received CNFs present an electrical conductivity of ~320 S m−1 and an interesting phenomenon of showing negative S-values of −5.5 μVK−1, with 10−2 µW/mK2 as the power factor (PF). In contrast, the PP/CNF composites with 5 wt. % of CNFs showed lower conductivities of ~50 S m−1, less negative S-values of −3.8 μVK−1, and a PF of 7 × 10−4 µW/mK2. In particular, the change in the Seebeck coefficient of the PP/CNF composites is explained by a slight electron donation from the outer layers of the CNFs to the PP molecules, which could reduce the S-values of the as-received CNFs. Our study indicates that even insulating polymers such as PP may have a quantifiable effect on the intrinsic Seebeck coefficient of carbon-based nanostructures, and this fact should also be taken into consideration to tailor conductive polymer composites with the desired thermoelectric (TE) properties.The authors affiliated with 2C2T acknowledge support from FCT-Foundation for Science and Technology within the scope of project UID/CTM/00264/2020. In addition, support through project IF/ A. J. Paleo et al. 00894/2015 and within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 and UIDP/50011/2020 and access to the Navigator platform (LCA-UC) through the Advanced Computing Project CPCA/A2/2524/2020, financed by national funds through the Portuguese Foundation for Science and Technology I.P./ MCTES, is gratefully acknowledged