Estudi de performances d'enlairament d'avions pel disseny de procediments d'atenuacio de soroll

Aquest projecte es una contribucio a la recerca vigent que tracta de minimitzar l'impacte acustic produit per les aeronaus en operacions d'enlairament. En concret, el present treball es centra en l'estudi de la distancia respecte la capcalera de pista on s'inicia el procediment d'atenuacio del soroll, sense entrar en detall en la definicio de les maniobres posteriors que el defineixen. Tot l'estudi es desenvolupa pels models d'avio A320 i A321 d'Airbus i considerant 5 destinacions europees tipiques des de l'aeroport de Girona-Costa Brava. La distancia a la qual s'inicien aquests tipus de procediments es la corresponent a quan l'avio es troba a 400 ft d'alcada per sobre la pista. Aixi doncs, aquesta distancia pot afectar el disseny final dels procediments d'atenuacio de soroll que es defineixin a l'aeroport. Juntament amb aquesta distancia, calculem les distancies d'enlairament TOR (Take Off Runway) i TOD (Take Off Distance) necessaries segons la configuracio de performance de l'avio per a cada vol. D'altra banda hem comprovat l'afectacio dels obstacles de la pista en les distancies d'enlairament. Per tal d'assolir els objectius proposats s'ha utilitzat un programari desenvolupat per Airbus (Performance Engineering Program) que duu a terme simulacions de vols complets, calculant-ne tots els parametres. A causa de l'extensa quantitat de dades i arxius a processar, s'ha automatitzat el proces d'introduccio i processament de dades mitjancant scripts dissenyats i programats amb llenguatge Bash-Shell. Finalment, hem comprovat i verificat que la distancia a la que ha d'iniciar-se el procediment d'atenuacio del soroll es major volant amb el model A321, a la destinacio mes llunyana, amb velocitat d'enlairament maxima, amb el maxim payload amb el major valor de cost index i amb configuracio de flaps/slats a l'enlairament CONF 1+F. La presencia dels obstacles al voltant de la pista, provoca un augment a les distancies necessaries TOR i TOD pero no influeix a la distancia on s'inicia el procediment d'atenuacio (400 ft d'alcada). Pel que fa a l'afectacio del cost index a aquestes distancies hem determinat que aquest practicament no les fa variar. El valor maxim de la distancia a la que s'inicia el procediment d'atenuacio del soroll es de 2865 m mentre que el minim es de 1545 m

Computational Modeling of Molecular Magnetic Materials

[cat] Els materials moleculars han despertat molt d'interès en les últimes dècades degut a la seva possible aplicació en nous dispositius multifuncionals. Entre les diferents propietats que aquests materials poden presentar, una de les més típiques és el magnetisme, el qual sorgeix de la presència d’electrons desaparellats en les molècules que constitueixen el cristall tridimensional. El magnetisme té un observable macroscòpic, la susceptibilitat magnètica (Ji), que sol ser racionalitzada en termes microscòpics mitjançant el conjunt d'interaccions magnètiques JAB entre determinats parells de molècules. No obstant això, cap tècnica experimental permet aquesta correspondència directa i, per tant, la interpretació experimental de les propietats magnètiques sol requerir d’un posterior anàlisi des del punt de vista de la química computacional. La present tesi doctoral pretén doncs contribuir en el camp del magnetisme molecular i, més concretament, en com es poden utilitzar les eines de la química computacional per a modelitzar materials magnètics moleculars des de diferents perspectives. Amb aquest objectiu en ment, s’han racionalitzat les propietats magnètiques de diversos sistemes d'interès, que van des de compostos metal•lorgànics basats en ions de Cu(II) o de Co(II), radicals orgànics purs, compostos basats en l’estratègia sintètica de “metall-radical”, i finalment també materials de spin crossover basats en Fe(II). Al llarg de la tesi s'ha demostrat que la química computacional és una disciplina útil, capaç d'ajudar a la interpretació dels resultats experimentals i en la predicció de propietats interessants, especialment quan es treballa en estreta col•laboració amb els experimentadors. En particular, el procediment de primers principis Bottom-Up (FPBU, per les seves sigles en anglès), desenvolupat àmpliament en el nostre grup, és una eina útil per racionalitzar les propietats magnètiques de qualsevol material magnètic molecular. Per a aquest propòsit, la topologia magnètica (és a dir, la xarxa de JAB dins del cristall) és l'element clau. A més, hem analitzat diversos factors que afecten aquesta topologia magnètica, com els contraions, els radicals diamagnètics o l’efecte de la temperatura, mitjançant la seva manifestació en les vibracions del cristall i en la contracció (expansió) que pateix al refredar-se (escalfar-se).[eng] Molecular materials have raised much interest in the last decades in the quest for new multifunctional devices. Among the multiple properties that those materials may present, one of the most typical is magnetism, which arises from the presence of unpaired electrons in the molecules that constitute the three-dimensional crystal. Magnetism has a macroscopic observable, the magnetic susceptibility (Ji), which is usually rationalized in terms of a set of JAB magnetic interactions between pairs of molecules. However, any experimental technique allows for such direct correspondence and, thus, the experimental interpretation of the magnetic properties usually requires further analysis from the point of view of computational chemistry. Consequently, the present PhD thesis is a contribution to the computational modeling of molecule-based magnetic materials. Specifically, we describe how the tools of computational chemistry may be used in order to study those materials from different perspectives. With this aim in mind, we have applied computational chemistry techniques to rationalize the magnetic properties of several systems of interest, ranging from metal-organic compounds, based on Cu(II), to pure organic radicals based on the DTA and Benzotriazinyl building blocks, and including compounds based on the metal-radical synthetic approach, and also spin crossover materials based on Fe(II). Along the thesis we have demonstrated that computational chemistry is a helpful discipline, capable to aid in the interpretation of experimental results and in the prediction of interesting properties, especially when working in close collaboration with experimentalists. In particular, the First Principles Bottom-Up (FPBU) procedure, extensively developed in our group, is a useful tool to rationalize the magnetic properties of any molecular magnetic material. To this purpose, the magnetic topology (i.e. the network of JAB within the crystal) is the key element. Regarding the magnetic topology, we have also demonstrated that it can be more intricate and complex than expected, and that it cannot be directly inferred from the coordination pattern of the molecule-based material. Therefore, the experimental assignation of the magnetic topology, by means of a fitting procedure, must be taken with caution. About the JAB values, we have proved that they depend on temperature, and that this dependence may be especially important when working with organic radicals. On this class of materials, we have analyzed how the JAB values evolve with time, and seen that this evolution may involve huge fluctuations of their magnitude as a consequence of the thermal motion at finite temperatures. Interestingly, we demonstrate herein that, when the JAB values depend non-linearly with the thermal vibrations of a material, the standard static perspective of magnetism is not valid to fully understand their magnetic properties, and that it is then required to adopt a dynamic perspective. Regarding the computational modeling of JAB values, we have seen that the combination of UB3LYP and the Broken-Symmetry approach yields JAB values, when transformed into the macroscopic observables, are in good agreement with experiment. In fact, we have demonstrated that, in order to predict the strength of a given JAB value, small distortions in the crystal structure can induce large variations, which may be much more important than the intrinsic error associated with the theoretical method employed. We have also observed that the counterions and diamagnetic ligands may have an important effect in defining the magnetic properties of a system. Overall, we have demonstrated that the magnetic topology and, thus, the macroscopic magnetic properties of a given material, cannot be understood without the proper knowledge of their crystal structure

On the zeroth-order Hamiltonian for CASPT2 calculations of spin crossover compounds

Complete active space self-consistent field theory (CASSCF) calculations and subsequent second-order perturbation theory treatment (CASPT2) are discussed in the evaluation of the spin-states energy difference (ΔHelec) of a series of seven spin crossover (SCO) compounds. The reference values have been extracted from a combination of experimental measurements and DFT  +  U calculations, as discussed in a recent article (Vela et al., Phys Chem Chem Phys 2015, 17, 16306). It is definitely proven that the critical IPEA parameter used in CASPT2 calculations of ΔHelec, a key parameter in the design of SCO compounds, should be modified with respect to its default value of 0.25 a.u. and increased up to 0.50 a.u. The satisfactory agreement observed previously in the literature might result from an error cancellation originated in the default IPEA, which overestimates the stability of the HS state, and the erroneous atomic orbital basis set contraction of carbon atoms, which stabilizes the LS states

Lattice-solvent effects in the spin-crossover of an Fe(II)-based material. The key role of intermolecular interactions between solvent molecules

The spin transition of Fe(II) complexes is the subject of intensive synthetic and computational efforts. In this manuscript, we analyze the spin crossover (SCO) of [Fe(Edpsp)(2)](2+) (1), which features a spin transition depending on the cocrystallizing solvent molecules. Whereas the use of acetone results in a hysteretic spin transition at similar to 170 K, the use of propylene carbonate (PC) results in a permanent diamagnetic signal up to 300 K. By means of DFT+U+D2 calculations in the solid state of the material, we unravel the reasons for such different behavior. Our results allow us to ascribe the relatively low transition temperature of 1(BF4)(2.) acetone to the distorted arrangement of the SCO molecules in the low-spin state of the material. In turn, intermolecular interactions play the primary role in the case of 1(BF4)(2).2PC. In particular, we found that solvent-solvent interactions actively promote the stability of the low-spin state due to the formation of PC dimers. These dimers would appear at larger distances in the high-spin phase, with the subsequent loss of phase stability. This is yet another proof of how subtle is the spin transition phenomenon in Fe(II)-based architectures

Controlling the crystallinity and crystalline orientation of “shuttlecock” naphthalocyanine films for near-infrared optoelectronic applications

The thin film properties of tin(II) 2,3-naphthalocyanine (SnNPc) were interrogated and various strategies for controlling the crystallinity and crystalline orientation within the films were assessed. SnNPc is shown to crystallize in the space group P21/c (Z = 4), where the molecular arrangement consists of alternating layers of concave and convex overlap, induced by the out-of-plane Sn atoms, resulting in a 3D slipped-π-stack network structure analogous to that reported for Phase I of titanyl phthalocyanine. The thin films were studied by X-ray diffraction, atomic force microscopy and absorption spectroscopy and are highly sensitive not just to the conditions during growth, but also to substrate pre- and post-deposition treatment. While the films grown at room temperature were largely amorphous, the crystallinity was enhanced with substrate temperature, with the molecules orienting in a standing molecular geometry. A thin layer of 3,4:9,10-perlenetetracarboxylic dianhydride induces a lying molecular geometry of the same polymorph as that of the single crystal, while different polymorphs are accessible through solvent vapor annealing of amorphous films. Transient photocurrent measurements showed a dramatic improvement in photodetector device bandwidth for the lying molecular geometry, which was attributed to enhanced photoconductivity along the π-stacking axis, while solvent vapor annealing could be used to tune the photosensitivity across the near-infrared region

Thermal spin crossover in Fe(ii) and Fe(iii). Accurate spin state energetics at the solid state

The thermal spin crossover (SCO) phenomenon refers to an entropy-driven spin transition in some materials based on d6-d9 transition metal complexes. While its molecular origin is well known, intricate SCO behaviours are increasingly common, in which the spin transition occurs concomitantly to e.g. phase transformations, solvent absorption/desorption, or order-disorder processes. The computational modelling of such cases is challenging, as it requires accurate spin state energies in the solid state. Density Functional Theory (DFT) is the best framework, but most DFT functionals are unable to balance the spin state energies. While a few hybrid functionals perform better, they are still too expensive for solid-state minima searches in moderate-size systems. The best alternative is to dress cheap local (LDA) or semi-local (GGA) DFT functionals with a Hubbard-type correction (DFT+U). However, the parametrization of U is not straightforward due to the lack of reference values, and because ab initio parametrization methods perform poorly. Moreover, SCO complexes undergo notable structural changes upon transition, so intra- and inter-molecular interactions might play an important role in stabilizing either spin state. As a consequence, the U parameter depends strongly on the dispersion correction scheme that is used. In this paper, we parametrize U for nine reported SCO compounds (five based on FeII, 1-5 and four based on FeIII, 6-9) when using the D3 and D3-BJ dispersion corrections. We analyze the impact of the dispersion correction treatments on the SCO energetics, structure, and the unit cell dimensions. The average U values are different for each type of metal ion (FeIIvs. FeIII), and dispersion correction scheme (D3 vs. D3-BJ) but they all show excellent transferability, with mean absolute errors (MAE) below chemical accuracy (i.e. MAE <4 kJ mol−1). This enables a better description of SCO processes and, more generally, of spin state energetics, in materials containing FeII and FeIII ions

Towards the tailored design of benzotriazinyl-based organic radicals displaying a spin transition

The mechanism of the phase transition of 1-phenyl-3-trifluoromethyl- 1,4-dihydrobenzo[e][1,2,4]triazin-4-yl (1), the first reported triazinyl radical to present such a feature, is unveiled. In so doing, we identify the key ingredients that are crucial to enable the phase transition in this family of radicals, and how those can be exploited by a rational design of the spin-carrying units

Three Redox States of a Diradical Acceptor−Donor−Acceptor Triad: Gating the Magnetic Coupling and the Electron Delocalization

The diradical acceptor–donor–acceptor triad 1••, based on two polychlorotriphenylmethyl (PTM) radicals connected through a tetrathiafulvalene(TTF)–vinylene bridge, has been synthesized. The generation of the mixed-valence radical anion, 1•–, and triradical cation species, 1•••+, obtained upon electrochemical reduction and oxidation, respectively, was monitored by optical and ESR spectroscopy. Interestingly, the modification of electron delocalization and magnetic coupling was observed when the charged species were generated and the changes have been rationalized by theoretical calculations.This work was supported by the DGI grant (CTQ2013-40480- R), the Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN), and the Generalitat de Catalunya (grant 2014-SGR-17). ICMAB acknowledges support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-0496). M.S. is enrolled in the Material Science Ph.D. program of UAB and is grateful to MEC for a FPU predoctoral grant. S.V. and M.F. are thankful to the LabEx-Chemistry of Complex Systems for postdoctoral grants (ANR-10-LABX-0026CSC) and to the regional High-Performance Computing (HPC) center in Strasbourg for computational resources. We thank Amable Bernabé for the MALDI spectroscopy.Peer reviewe

Tracing the sources of the different magnetic behavior in the two phases of the bistable (BDTA)2[Co(mnt)2] compound

A complete computational study of the magnetic properties of the two known phases of the bistable (BDTA)2[Co(mnt)2] compound is presented. The origin of their different magnetic properties can be traced to a variation in the values of the g tensor, together with a hitherto unknown change in the JAB values and their magnetic topology

Pitfalls on evaluating pair exchange interactions for modelling molecule-based magnetism

Molecule-based magnetism is a solid-state property that results from the microscopic interaction between magnetic centres or radicals. The observed magnetic response is due to unpaired electrons whose coupling leads to a particular magnetic topology. Therefore, to understand the magnetic response of a given molecule-based magnet and reproduce the available experimental magnetic properties by means of statistical mechanics, one has to be able to determine the value of the J(AB) magnetic exchange coupling between radicals. The calculation of J(AB) is thus a key point for modelling molecule-based magnetism. In this Perspectives article, we will build upon our experience in modelling molecular magnetism to point out some pitfalls on evaluating J(AB) couplings. Special attention must be paid to the cluster models used to evaluate J(AB), which should account for cooperative effects among J(AB) interactions and also consider the environment (counterions, hydrogen bonding) of the two radicals whose interaction has to be evaluated. It will be also necessary to assess whether a DFT-based or a wavefunction-based method is best to study a given radical. Finally, in addition to model and method, the J(AB) couplings have to be able to adapt to changes in the magnetic topology due to thermal fluctuations. Therefore, it is most important to appraise in which systems molecular dynamics simulations would be required. Given the large number of issues one must tackle when choosing the correct model and method to evaluate J(AB) interactions for modelling magnetic properties in molecule-based materials, the "human factor" is a must to cross-examine and challenge computations before trusting any result.MD, JRA, and JJN acknowledge financial support from MINECO (CTQ2017-87773-P/AEI/FEDER, UE), Spanish Structures Excellence Maria de Maeztu program (MDM-2017-0767), and Catalan DURSI (2017SGR348)