Física de Partículas

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Unsupervised clustering based coronary artery segmentation
(BioMed Central, 2025-03-07) Serrano Antón, Belén; Insúa Villa, Manuel; Pendón-Minguillón, Santiago; Paramés Estévez, Santiago; Otero Cacho, Alberto; López Otero, Diego; Díaz Fernández, Brais; Bastos-Fernández, María; González Juanatey, José Ramón; Pérez Muñuzuri, Alberto; Universidade de Santiago de Compostela. Departamento de Física de Partículas
Background: The acquisition of 3D geometries of coronary arteries from computed tomography coronary angiography (CTCA) is crucial for clinicians, enabling visualization of lesions and supporting decision-making processes. Manual segmentation of coronary arteries is time-consuming and prone to errors. There is growing interest in automatic segmentation algorithms, particularly those based on neural networks, which require large datasets and significant computational resources for training. This paper proposes an automatic segmentation methodology based on clustering algorithms and a graph structure, which integrates data from both the clustering process and the original images. Results: The study compares two approaches: a 2.5D version using axial, sagittal, and coronal slices (3Axis), and a perpendicular version (Perp), which uses the cross-section of each vessel. The methodology was tested on two patient groups: a test set of 10 patients and an additional set of 22 patients with clinically diagnosed lesions. The 3Axis method achieved a Dice score of 0.88 in the test set and 0.83 in the lesion set, while the Perp method obtained Dice scores of 0.81 in the test set and 0.82 in the lesion set, decreasing to 0.79 and 0.80 in the lesion region, respectively. These results are competitive with current state-of-the-art methods. Conclusions: This clustering-based segmentation approach offers a robust framework that can be easily integrated into clinical workflows, improving both accuracy and efficiency in coronary artery analysis. Additionally, the ability to visualize clusters and graphs from any cross-section enhances the method’s explainability, providing clinicians with deeper insights into vascular structures. The study demonstrates the potential of clustering algorithms for improving segmentation performance in coronary artery imaging.
Towards an optimally sensitive temperature probe in heavy-ion collisions
(Elsevier, 2025-12) López Pardo, Víctor; Rothkopf, Alexander; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
The high-precision heavy quarkonium data from LHC Run 2 and the ongoing Run 3 provide a unique window into the properties of hot nuclear matter and the Quark-Gluon Plasma (QGP). To make full use of this data, it is crucial to go beyond traditional observables such as the nuclear modification factor 𝑅𝐴𝐴 and elliptic flow 𝑣2, and instead develop new probes that are more directly sensitive to the characteristics of the medium. We adopt the open quantum systems perspective for in-medium quarkonium and take inspiration from cold atom metrology techniques to construct observables with optimal sensitivity to specific QGP parameters. Focusing on the bulk temperature, we develop such optimal observables based on the Caldeira-Leggett master equation as a simplified setup, with the goal of extending it to a full Quantum Brownian Motion Lindblad equation.
A fast and automated approach for urban CFD simulations: validation with meteorological predictions and its application to drone flights
(Elsevier, 2025-12) Suárez Vázquez, Marcos; Varela Ballesta, Sylvana; Otero Cacho, Alberto; Pérez Muñuzuri, Alberto; Mira Pérez, Jorge; Universidade de Santiago de Compostela. Departamento de Física Aplicada; Universidade de Santiago de Compostela. Instituto de Materiais (iMATUS); Universidade de Santiago de Compostela. Departamento de Física de Partículas
In past years, several studies have proposed new methods and applications for urban wind simulations, including geometry reconstruction from urban data sources or improved boundary condition definition. In this article, we present a fast and automated methodology for reconstructing airflows within urban environments using LiDAR and cadastral data coupled with Computational Fluid Dynamics (CFD) simulations. Our approach integrates meteorological predictions with computational techniques to simulate the complex interactions between wind currents, buildings, vegetation, water zones and terrain morphology within urban environments. Accurate boundary conditions based on meteorological predictions are introduced into a coupled methodology that directly creates the terrain shape inside the simulation environment, simplifying the geometry creation process, which is one of the most prevalent problems in CFD urban simulations. The simulation results are confronted against ground-truth real data obtained from a meteorological station, showing strong agreement with the outcomes generated by the proposed CFD model, with a concordance correlation coefficient up to ρ and ρ c c =0.985 for the wind direction =0.853 for the wind speed. The results from these simulations are then used for validating a wind tunnel approach that mimics the interaction between a moving drone and the extracted wind currents, demonstrating a great improvement in computation times when compared to the most straightforward approach that consists in embedding the drone within the full urban landscape. This research contributes to the advancement of urban CFD modeling, and it has significant implications for various applications, providing valuable insights for urban development.
Primary scintillation yields induced by α particles in gas mixtures of Argon/CF4 at 9.5 bar
(Springer Nature, 2025-02-14) Amedo, Pablo; Leardini, Sara; Saá Hernández, Ángela; González Díaz, Diego; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
We report time and band -resolved scintillation from α-particles in Ar/CF4 mixtures at a pressure of 9.5 bar. Our results show that %-level addition of CF4 enables strong wavelength-shifted scintillation in the visible range, with yields at the level of 1000 ph/MeV, scintillation decay times of 9–25 ns and formation times well below 10 ns. Such a performance is a priori sufficient for accurate time-tagging of MeV-particles, without the need to resort to a pure noble gas, thus opening an appealing technological path for next-generation time projection chambers.
Strangeness production in pp and pPb collisions at LHCb
(EDP Sciences, 2025-01-27) Landesa Gómez, Clara; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
Strange hadron production provides information about the hadronisation process in high-energy hadron collisions. Strangeness enhancement has been interpreted as a signature of quark-gluon plasma formation in heavy-ion collisions, and recent observations of strangeness enhancement in small collision systems have challenged conventional hadronisation models. With its forward geometry and excellent particle identification capabilities, the LHCb detector is well-suited to study strangeness production in a unique kinematic region. Recent studies of strangeness production with the LHCb detector are presented, including measurements of strangeness enhancement in the charm- and beauty-hadron systems.
Surface-engineered gold nanorods for targeted delivery of PD-L1 siRNA and cancer chemo-phototherapy
(Royal Society of Chemistry, 2025-10-09) Arellano, Lilia; Villar Álvarez, Eva; Cambón Freire, Adriana; Costa Santos, Alba; Pardo Montero, Alberto; Topete Camacho, Antonio; Barbosa Fernández, Silvia; Taboada Antelo, Pablo; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto de Materiais (iMATUS)
Nowadays, cancer remains a global leading cause of death, with therapeutic advances often hindered by drug resistance and adverse side effects. The integration of nanotechnology with immunotherapy has emerged as a promising approach to enhance specificity and efficacy of oncological treatments. A key immunotherapeutic target is the so-called programmed death-ligand 1 (PD-L1), a protein that enables tumors to evade immune surveillance and increase their chemotherapy resistance. Interestingly, RNA interference using small interfering RNA (siRNA) targeting PD-L1, has shown potential in reactivating anti-cancer immune responses. However, efficient delivery of siRNA still faces challenges in terms of stability, cellular uptake, and/or targeted release. In this study, we developed a multifunctional theranostic nanoplatform based on gold nanorods (GNRs) surface-engineered through a layer-by-layer assembly with poly(styrene sulfonate), poly(L-lysine), and hyaluronic acid, to provide enhanced stability and active targeting towards CD44 receptors overexpressed in cancer cells. Within the polymeric multilayers PD-L1 siRNA, doxorubicin and indocyanine green were loaded for multimodal therapeutic activity. The anti-tumor effect, siRNA transfection efficiency and cell death mechanism of the nanoplatform was evaluated on HeLa cells expressing PD-L1 and CD44 and Balb/3T3 fibroblasts. The surface-engineered GNRs-based nanosystem efficiently transfected PD-L1 siRNA and allowed subsequent application of multimodal chemo-, photodynamic and photothermal therapy with enhanced cytotoxicity.
Automatic Optimization of a Parallel-Plate Avalanche Counter with Optical Readout
(MDPI, 2025) Pereira Martínez, Maria; Cid Vidal, Xabier; Vischia, Pietro; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
An automatic optimization procedure is proposed for some operational parameters of a Parallel-Plate Avalanche Counter with Optical Readout, a detector designed for heavy-ion tracking and imaging. Exploiting differentiable programming and automatic differentiation, we model the reconstruction of the position of impinging 5.5 MeV alpha particles for different detector configurations and build an optimization cycle that minimizes an objective function. We analyze the performance improvement using this method, exploring the potential of these techniques in detector design.
Hot wormholes and chaos dynamics in a two-coupled SYK model
(Springer, 2025-03-14) Berenguer Mimó, Martí; Mas Solé, Javier; Santos Suárez, Juan; Vázquez Ramallo, Alfonso; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
We study the dynamics of chaos across the phase transition in a 2-coupled Sachdev-Ye-Kitaev (SYK) model, with a focus on the unstable “hot wormhole” phase. Using the Schwinger-Keldysh formalism, we employ two non-equilibrium protocols that allow access to this phase, which is inaccessible through equilibrium simulations: one involves cooling the system via a coupling to a thermal bath, while in the other we periodically drive the coupling parameter between the two sides. We numerically compute the Lyapunov exponents of the hot wormhole for the two cases. Our results uncover a rich structure within this phase, including both thermal and non-thermal solutions. These behaviors are analyzed in detail, with partial insights provided by the Schwarzian approximation, which captures certain but not all aspects of the observed dynamics.
Assessing the best hour to start the day: an appraisal of seasonal daylight saving time
(The Royal Society, 2025-03-19) Martín Olalla, José María; Mira Pérez, Jorge; Universidade de Santiago de Compostela. Departamento de Física Aplicada; Universidade de Santiago de Compostela. Instituto de Materiais (iMATUS)
We provide an evidence-based position on the seasonal regulation of clocks daylight saving time (DST) that challenges position papers by sleep associations against the practice. We review the acute, short-term impact and the chronic, long-term impact of DST in the context of the changing ambient light conditions that characterize seasons at Extratropical latitudes. We highlight the association between DST, human physiology (photoreceptive mechanisms) and human daily life. We offer a perspective on the possible scenarios should clock regulations be abandoned.
Personalized medicine to treat refractory benign paroxysmal positional vertigo, through computational fluid dynamics analysis from magnetic resonance image reconstructions
(Frontiers Media, 2025) Rossi Izquierdo, Marcos; Santos Pérez, Sofía María de la Soledad; Arán Tapia, Ismael; Blanco Ulla, Miguel; Arán González, Ismael; Vaamonde Sánchez-Andrade, Isabel; Franco-Gutiérrez, Virginia; Pérez Muñuzuri, Vicente; Pérez Muñuzuri, Alberto; Soto Varela, Andrés; Universidade de Santiago de Compostela. Departamento de Cirurxía e Especialidades Médico-Cirúrxicas; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Centro Interdisciplinar de Investigación en Tecnoloxías Ambientais (CRETUS)
Background: Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo, often effectively treated with standard canalith repositioning maneuvers (CRMs). However, approximately 12.5% of cases remain refractory, leading to persistent symptoms and increased healthcare burden. Variations in the anatomical orientation of the semicircular canals (SCCs) may explain the resistance to conventional maneuvers. This study explores a personalized medicine approach, utilizing computational fluid dynamics (CFD) based on MRI reconstructions to tailor CRMs with the help of mechanical rotation chair according to individual inner ear anatomy. Methods: We conducted a randomized, multicenter, open-label study targeting patients with refractory posterior canal BPPV. Participants were allocated to either a control group (receiving repeated standard CRMs and Brandt-Daroff exercises) or an intervention group (receiving personalized CRMs based on CFD simulations derived from MRI scans). The intervention group’s maneuvers were executed using a mechanical rotational chair designed for precise angulation. Primary outcomes included resolution of nystagmus and vertigo symptoms, while secondary outcomes measured the reduction in healthcare visits and improved quality of life (Dizziness Handicap Inventory score). Discussion: Personalized CRMs based on CFD models may enhance treatment efficacy for refractory BPPV by optimizing maneuver angles according to the specific SCC orientation. This approach could significantly reduce symptom persistence, decrease the need for repeated healthcare visits, and improve patient outcomes. The use of non-invasive MRI and CFD techniques represents a novel step toward individualized treatment in vestibular disorders, with potential for broader application in personalized otoneurology. Further analysis will determine the extent of clinical benefit and cost-effectiveness of this approach. Clinical trial registration: ClinicalTrials.gov, Identifier: NCT06725966.
Towards a new generation of solid total-energy detectors for neutron-capture time-of-flight experiments with intense neutron beams
(Elsevier, 2024-11-30) Balibrea-Correa, Javier; Caamaño Fresco, Manuel; Durán Escribano, Ignacio; Fernández Domínguez, Beatriz; Žugec, Petar C.; Universidade de Santiago de Compostela. Departamento de Física de Partículas
Challenging neutron-capture cross-section measurements of small cross sections and samples with a very limited number of atoms require high-flux time-of-flight facilities. In turn, such facilities need innovative detection setups that are fast, have low sensitivity to neutrons, can quickly recover from the so-called γ-flash, and offer the highest possible detection sensitivity. In this paper, we present several steps towards such advanced systems. Specifically, we describe the performance of a high-sensitivity experimental setup at CERN n_TOF EAR2. It consists of nine sTED detector modules in a compact cylindrical configuration, two conventional used large-volume C6D6 detectors, and one LaCl3(Ce) detector. The performance of these detection systems is compared using 93Nb(n, γ) data. We also developed a detailed GEANT4 Monte Carlo model of the experimental EAR2 setup, which allows for a better understanding of the detector features, including their efficiency determination. This Monte Carlo model has been used for further optimization, thus leading to a new conceptual design of a γ detector array, STAR, based on a deuterated-stilbene crystal array. Finally, the suitability of deuterated-stilbene crystals for the future STAR array is investigated experimentally utilizing a small stilbene-d12 prototype. The results suggest a similar or superior performance of STAR with respect to other setups based on liquid-scintillators, and allow for additional features such as neutron-gamma discrimination and a higher level of customization capability.
US Corn Belt enhances regional precipitation recycling
(National Academy of Sciences, 2024-12-30) Zhang, Zhe; He, Cenlin; Chen, Fei; Míguez Macho, Gonzalo; Liu, Changhai; Rasmussen, Roy; Universidade de Santiago de Compostela. Departamento de Física de Partículas
Precipitation recycling, where evapotranspiration (ET) from the land surface contributes to precipitation within the same region, is a critical component of the water cycle. This process is especially important for the US Corn Belt, where extensive cropland expansions and irrigation activities have significantly transformed the landscape and affected the regional climate. Previous studies investigating precipitation recycling typically relied on analytical models with simplifying assumptions, overlooking the complex interactions between groundwater hydrology and agricultural management. In this study, we use high-resolution climate models coupled with an explicit water vapor tracer algorithm to quantify the impacts of shallow groundwater, dynamic crop growth, and irrigation on regional precipitation recycling in the US Corn Belt. We find that these coupled groundwater–crop–irrigation processes reduce surface temperatures and increase the growing season precipitation. The increase in precipitation is attributed to a significant enhancement of the precipitation recycling ratio from 14 to 18%. This enhanced precipitation recycling is stronger in a dry year than normal and wet years, depending on both large-scale moisture transport and local ET. Our study underscores the critical role of groundwater hydrology and agricultural management in altering the regional water cycle, with important implications for regional climate predictions and food and water security.
Exploring the Dietary Patterns and Health Behaviours of Centenarians in Ourense (Spain): Adherence to the Southern European Atlantic Diet
(MDPI, 2025-07-05) García Vivanco, Pablo; Taboada Antelo, Pablo; Cepeda Sáez, Alberto; Coelho Cotón, Alberto José; Universidade de Santiago de Compostela. Departamento de Química Orgánica; Universidade de Santiago de Compostela. Instituto de Materiais (iMATUS); Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Departamento de Química Analítica, Nutrición e Bromatoloxía
Background: Understanding the multifactorial determinants of human longevity remains a major scientific challenge. Certain regions of the world—so-called “longevity hotspots”—exhibit a notably high prevalence of centenarians; one such region is the province of Ourense, in north-western Spain. Objectives: This study aimed to analyse, for the first time, the nutritional factors associated with healthy longevity among centenarians, as well as those linked to longevity irrespective of health status, in the province of Ourense. Methods: A cross-sectional, retrospective, observational, mixed-methods study was conducted. A population of 261 individuals aged 100 or over residing in Ourense was identified. A sample of 156 participants was included in the quantitative analysis; from this sample, 25 centenarians were selected for in-depth qualitative analysis through personal interviews. Results: Dietary patterns aligned with the Southern European Atlantic Diet (SEAD), combined with strong social bonds and a culture of self-sufficiency, appear to be key contributors to exceptional longevity in this population. Conclusions: Remarkable longevity in Ourense is associated with a combination of factors: adherence to an SEAD-style dietary pattern, an active and uncomplicated lifestyle, and strong social support networks.
Development of a silicon bulk radiation damage model for Sentaurus TCAD
(Elsevier, 2017-12-01) Folkestad, Å.; Akiba, K.; Beuzekom, M. van; Buchanan, E.; Collins, P.; Dall'Occo, E.; Canto, A. Di; Evans, T.; Franco Lima, V.; García Pardiñas, Julián; Schindler, H.; Vicente, M.; Vieites Díaz, María; Williams, M.; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
This article presents a new bulk radiation damage model for p-type silicon for use in Synopsys Sentaurus TCAD. The model is shown to provide agreement between experiment and simulation for the voltage dependence of the leakage current and the charge collection efficiency, for fluences up to 8 × 1015 1 MeV neq∕cm2 .
Molecular dynamics simulations of the structure of the graphene–ionic liquid/alkali salt mixtures interface
(Royal Society of Chemistry, 2014-05-29) Méndez-Morales, Trinidad; Carrete Montaña, Jesús; Pérez Rodríguez, Martín; Cabeza Gras, Oscar; Gallego del Hoyo, Luis Javier; Lynden-Bell, Ruth; Varela Cabo, Luis Miguel; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto de Materiais (iMATUS)
We performed molecular dynamics simulations of mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate with lithium tetrafluoroborate and potassium tetrafluoroborate between two charged and uncharged graphene walls, in order to analyze the structure of the well-known formation of layers that takes place on liquids under confinement. For this purpose, we studied the molecular density profiles, free energy profiles for bringing lithium and potassium cations from the bulk mixture to the graphene wall and the orientational distributions of imidazolium rings within the first adsorbed layer as a function of salt concentration and electrode potential. The charge densities in the electrodes were chosen to be zero and ±1 e nm−2, and the salt molar percentages were %salt = 0, 10 and 25. We found that the layered structure extends up to 1–2 nm, where the bulk behaviour is recovered. In addition, whereas for the neutral surface the layers are composed of both ionic species, increasing the electrode potential, the structure changes to alternating cationic and anionic layers leading to an overcompensation of the charge of the previous layer. We also calculated the distribution of angles of imidazolium rings near neutral and charged graphene walls, finding a limited influence of the added salt. In addition, the average tilt of the imidazolium ring within the first layer goes from 36° with respect to a normal vector to the uncharged graphene wall to 62° in the presence of charged walls. The free energy profiles revealed that lithium and potassium ions are adsorbed on the negative surface only for the highest amount of salt, since the free energy barriers for approaching this electrode are considerably higher than kBT
Molecular dynamics simulation of the structure and dynamics of water–1-Alkyl-3-methylimidazolium ionic liquid mixtures
(American Chemical Society, 2011-06-02) Méndez-Morales, Trinidad; Carrete Montaña, Jesús; Cabeza Gras, Oscar; Gallego del Hoyo, Luis Javier; Varela Cabo, Luis Miguel; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto de Materiais (iMATUS)
We have performed extensive molecular dynamic simulations to analyze the influence of cation and anion natures, and of water concentration, on the structure and dynamics of water–1-alkyl-3-methylimidazolium ionic liquid mixtures. The dependence on water concentration of the radial distribution functions, coordination numbers, and hydrogen bonding degree between the different species has been systematically analyzed for different lengths of the cation alkyl chain (alkyl = ethyl, butyl, hexyl, and octyl) and several counterions. These include two halogens of different sizes and positions in Hoffmeister series, Cl– and Br–, and the highly hydrophobic inorganic anion PF6– throughout its whole solubility regime. The formation of water clusters in the mixture has been verified, and the influences of both anion hydrophobicity and cation chain length on the structure and size of these clusters have been analyzed. The water cluster size is shown to be relatively independent of the cation chain length, but strongly dependent on the hydrophobicity of the anion, which also determines critically the network formation of water and therefore the miscibility of the ionic liquid. The greater influence of the anion relative to the cation one is seen to be reflected in all the analyzed physical properties. Finally, single-particle dynamics in IL–water mixtures is considered, obtaining the self-diffusion coefficients and the velocity autocorrelation functions of water molecules in the mixture, and analyzing the effect of cation, anion, and water concentration on the duration of the ballistic regime and on the time of transition to the diffusive regime. Complex non-Markovian behavior was detected at intermediate times within an interval progressively shorter as water concentration increases
Mixtures of protic ionic liquids and molecular cosolvents: A molecular dynamics simulation
(AIP Publishing, 2014-06-02) Docampo Álvarez, Borja; Gómez González, Víctor; Méndez-Morales, Trinidad; Carrete Montaña, Jesús; Rodríguez, Julio R.; Cabeza Gras, Oscar; Gallego del Hoyo, Luis Javier; Varela Cabo, Luis Miguel; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto de Materiais (iMATUS)
In this work, the effect of molecular cosolvents (water, ethanol, and methanol) on the structure of mixtures of these compounds with a protic ionic liquid (ethylammonium nitrate) is analyzed by means of classical molecular dynamics simulations. Included are as-yet-unreported measurements of the densities of these mixtures, used to test our parameterized potential. The evolution of the structure of the mixtures throughout the concentration range is reported by means of the calculation of coordination numbers and the fraction of hydrogen bonds in the system, together with radial and spatial distribution functions for the various molecular species and molecular ions in the mixture. The overall picture indicates a homogeneous mixing process of added cosolvent molecules, which progressively accommodate themselves in the network of hydrogen bonds of the protic ionic liquid, contrarily to what has been reported for their aprotic counterparts. Moreover, no water clustering similar to that in aprotic mixtures is detected in protic aqueous mixtures, but a somehow abrupt replacing of [NO3]− anions in the first hydration shell of the polar heads of the ionic liquid cations is registered around 60% water molar concentration. The spatial distribution functions of water and alcohols differ in the coordination type, since water coordinates with [NO3]− in a bidentate fashion in the equatorial plane of the anion, while alcohols do it in a monodentate fashion, competing for the oxygen atoms of the anion. Finally, the collision times of the different cosolvent molecules are also reported by calculating their velocity autocorrelation functions, and a caging effect is observed for water molecules but not in alcohol mixtures
Molecular dynamics simulations of the structural and thermodynamic properties of imidazolium-based ionic liquid mixtures
(American Chemical Society, 2011-09-07) Méndez-Morales, Trinidad; Carrete Montaña, Jesús; Cabeza Gras, Oscar; Gallego del Hoyo, Luis Javier; Varela Cabo, Luis Miguel; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto de Materiais (iMATUS)
In this work, extensive molecular dynamics simulations of mixtures of alcohols of several chain lengths (methanol and ethanol) with the ionic liquids (ILs) composed of the cation 1-hexyl-3-methylimidazolium and several anions of different hydrophobicity degrees (Cl–, BF4–, PF6–) are reported. We analyze the influence of the nature of the anion, the length of the molecular chain of the alcohol, and the alcohol concentration on the thermodynamic and structural properties of the mixtures. Densities, excess molar volumes, total and partial radial distribution functions, coordination numbers, and hydrogen bond degrees are reported and analyzed for mixtures of the ILs with methanol and ethanol. The aggregation process is shown to be highly dependent on the nature of the anion and the size of the alcohol, since alcohol molecules tend to interact predominantly with the anionic part of the IL, especially in mixtures of the halogenated IL with methanol. Particularly, our results suggest that the formation of an apolar network similar to that previously reported in mixtures of ILs with water does not take place in mixtures with alcohol when the chloride anion is present, the alcohol molecules being instead homogeneously distributed in the polar network of IL. Moreover, the alcohol clusters formed in mixtures of [HMIM][PF6] with alcohol were found to have a smaller size than in mixtures with water. Additionally, we provide a semiquantitative analysis of the dependence of the hydrogen bonding degree of the mixtures on the alcohol concentration.
Dynamical properties of alcohol+ 1-hexyl-3-methylimidazolium ionic liquid mixtures: a computer simulation study
(ACS Publications, 2011-12-29) Méndez-Morales, Trinidad; Carrete, Jesús; García, Manuel; Cabeza Gras, Óscar; Gallego del Hoyo, Luis Javier; Varela Cabo, Luis Miguel; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto de Materiais (iMATUS)
In this work, extensive molecular dynamics simulations of the dynamics of mixtures of ionic liquids (ILs) composed of the cation 1-hexyl-3-methylimidazolium and several anions of different hydrophobicity degrees (Cl–, BF4–, PF6–) with alcohols of different chain lengths (methanol and ethanol) are reported. We evaluated the influence of the nature of the anion, the length of the molecular chain of the alcohol, and the alcohol concentration on some dynamical properties of the mixtures, such as self-diffusion coefficients of all the species, mean square displacements (with an analysis of both ballistic and diffusive regimes), and velocity autocorrelation functions of alcohol molecules. The diffusivity of the mixtures was found to be highly dependent on the nature of the anion since the interaction between chloride and alcohols is greater than that with fluorinated anions and leads to slower dynamics. Additionally, our results show that self-diffusion coefficients increase with alcohol concentration. On the other hand, a subdiffusive regime over thousands of picoseconds was detected at intermediate times through analysis of the center-of-mass mean square displacements of alcohol molecules, a region that becomes narrower as alcohol concentration increases. Finally, the study of the role of the anion and of solvent concentration on velocity autocorrelation functions reflects an increase in mean collision times as the amount of alcohol increases until the value of pure alcohols is reached. These collision times are smaller in mixtures with halogenated ILs
Density functional theory of alkali metals at the IL/graphene electrochemical interface
(American Institute of Physics, 2022-01-06) Montes-Campos, Hadrián; Rivera-Pousa, Alejandro; Méndez-Morales, Trinidad; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto de Materiais (iMATUS)
The mechanism of charge transfer between metal ions and graphene in the presence of an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) is investigated by means of density functional theory calculations. For that purpose, two different comparisons are established: (i) the behavior of Li+ and K+ when adsorbed onto the basal plane of graphene and (ii) the differences between Li+ approaching the carbon surface from the basal plane and being intercalated through the edge plane of trilayer graphene. In the first case, it is found that the metal ions must overcome high energy barriers due to their interaction with the ionic liquid before reaching an equilibrium position close to the interface. In addition, no significant charge transfer between any of the metals and graphene takes place until very close energetically unfavorable distances. The second configuration shows that Li+ has no equilibrium position in the proximity of the interface but instead has an equilibrium position when it is inside the electrode for which it has to cross an energy barrier. In this case, the formation of a LiC12 complex is observed since the charge transfer at the equilibrium distance is achieved to a considerable extent. Thus, the interfacial charge transfer resistance on the electrode in energy devices based on ionic liquids clearly depends not only on the binding of the ionic liquid to the metal cations and their ability to form a dense solvation shell around them but also on the surface topography and its effect on the ion packing on the surface.

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