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The bi–annual Meeting of the Spanish Neutron Scattering Association, VI RSETN, took place in the magnificent world heritage ancient city of Segovia, Spain, from 24–27 June 2012, at the historical building ''Palacio de Mansilla''. It was the sixth in a series of successful scientific meetings, beginning in 2002 (San Sebastián), and followed by conferences in Puerto de la Cruz (Canary Islands, 2004), Jaca (Aragón, 2006), Sant Feliú de Guixols (Cataluña, 2008) and Gijón (Asturias, 2010).

The conference covered a broad range of topics related to the use of neutron scattering techniques, from soft matter and biosciences to magnetism, condensed matter as well as advanced neutron instrumentation and applications. In addition to those topics, Spanish scientists working at neutron facilities reported recent upgrades of neutron instruments.

The VI RSETN was organized by a group of research scientists belonging to different institutions in Madrid: CSIC, Universidad Complutense and Universidad Politécnica de Madrid, in cooperation with the Spanish Society for Neutron Techniques (SETN, 'Sociedad Española de Técnicas Neutrónicas').

The meeting attracted around 90 participants. The total number of oral presentations was 36, including plenary and invited talks, both from domestic and foreign speakers. In addition, the number of posters was around 20. The success of the VI RSETN was due to the efforts of many colleagues involved at all stages of the meeting. We would like to thank the scientific committee, the local organizing committee, the chairs of the conference sessions as well as all the reviewers who agreed generously to help with the process. We would also like to emphasize the excellent scientific quality of all the presentations and posters, and we thank the support received from our sponsors (SETN, ICMM–CSIC, ESS–Bilbao, ILL, Carburos Metálicos), which was really important for the conference success.

Finally, we hope that the readers will enjoy the 28 scientific contributions contained in the present volume, which give an overview of the science and the engineering currently done by the Spanish neutron scattering community, a lively and growing community.

Jorge Hernández-Velasco, Carlos Cabrillo, Marta Castellote, Jesus Ruiz-Hervias Conference Proceedings Editors

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

This article briefly describes the basic design of the ESS-Bilbao neutron target station as well as its expected neutronic performance. The baseline engineering design, associated ancillary systems, and plant layout for the facility is now complete. A rotating target composed of twenty beryllium plates has been selected as the best choice in terms of both neutron yield and engineering complexity. It will provide neutron beams with a source term of 10¹⁵n s⁻¹ resulting from the direct ⁹Be(p, xn) reaction using a 75 mA proton beam at 50 MeV. The design envisages a target station equipped with two fully optimized moderators capable of withstanding a proton-beam power of 112 kW. This design is flexible enough to accommodate future upgrades in final proton energy. The envisaged neutron-beam brightness will enable several applications, including the use of cold and thermal neutrons for condensed matter research as well as fast-neutron irradiation studies. We close by discussing the role that this facility may play once the European Spallation Source becomes operational in Lund, Sweden.

Studies of the liquid state present an obvious fundamental interest and are also important for technological applications since the molten state is an essential stage in various industrial processes (e.g. glass making, single crystal growing, iron and steel making).

Most of the physical properties of a high-temperature liquid are related to its atomic structure. Thus it is important to develop devices to probe the local environment of the atoms in the sample. At very high temperature, it is difficult to use conventional furnaces, which present several problems. In particular, physical contact with the container can contaminate the sample and/or modify its structural properties. Such problems encouraged the development of containerless techniques, which are powerful tools to study high-temperature melts. By eliminating completely any contact between sample and container, it is possible to study the sample with a very high degree of control and to access very high temperatures. An additional advantage of levitation methods is that it is possible to supercool hot liquids down to several hundred of degrees below their equilibrium freezing point, since heterogeneous nucleation processes are suppressed.

D1B is a medium resolution high flux powder diffractometer located at the Institut Laue Langevin, ILL. D1B a suitable instrument for studying a large variety of polycrystalline materials. D1B runs since 1998 as a CRG (collaborating research group) instrument, being exploited by the CNRS (Centre National de la Recherche Scientifique, France) and CSIC (Consejo Superior de Investigaciones Cientificas, Spain). In 2008 the Spanish CRG started an updating program which included a new detector and a radial oscillating collimator (ROC). The detector, which has a sensitive height of 100mm, covers an angular range of 128°. Its 1280 gold wires provide a neutron detection point every 0.1°. The ROC is made of 198 gadolinium- based absorbing collimation blades, regular placed every 0.67°. Here the present characteristics of D1B are reviewed and the different experimental performances will be presented.

The new neutron vibrational spectrometer LAGRANGE replaces the Be filter spectrometer placed on the hot source at the Institut Laue-Langevin. Lagrange provides much higher sensitivity to extremely small or low scattering samples through substantially increased detector count rate combined with considerably improved energy resolution. It opens new possibilities for the spectroscopic studies of complex materials. The new instrument permits investigation of much smaller samples, inherent in novel materials studies, recording of well- resolved vibration spectra. Lagrange is fully operational for users since 2012.

In a recent article, the combined effects of the sample environment and instrument collimation have been described for the dedicated instrument for amorphous systems at ILL (D4) [1]. This undesirable effects on the diffractograms force to make complex and careful absorption corrections, which not always produce good enough results. In such cases, parts of the detector banks must be discarded with the consequent lose of statistics. This experimental problem can be used to obtain the transmission of the sample by an indirect way.

Considering the most generalized case of a cylindrical sample with a cylindrical sample environment (furnace, cryostat, etc), the diffractogram can be described as coming from three different sources: the sample itself, the upstream and downstream sample environment. These sources produce three well-differenced regions on the individual diffractograms observed by one particular detector. These three different measured signals are linear combination of the sample, upstream and downstream intensities produced by each source. In this way, upstream and downstream intensities can be determined, and the experimental transmission of the sample can be obtained. The experimental results corresponding to the standard cryostat are compared with the theoretical calculation of the transmission for a series of samples measured at D4 over the past years. This comparison shows that an undesirable effect observed on the diffractograms could even be useful under some circumstances.

This paper discusses the device and software used to carry out Cyclic Neutron Activation Analysis (CNAA). The aim of this investigation is defining through this device the fluorite content present on different samples from fluorspar concentration plant through the DGNAA (Delayed Gamma Neutron Activation Analysis) method. This device is made of americium-beryllium neutron source, NaI (2"×2") and BGO (2"×2") gamma rays detectors, multichannel and an automatic mechanism which moves the samples from activation and reading position. This mechanism is controlled by a software which allows moving the samples precisely and in a safe way (~ms), which it is very useful when the radioactive isotopes have to be detected with a half time less than 8s.

This paper studies two specific procedures for analyzing mining samples through a neutron activation technique called DGNAA (Delayed Gamma Neutron Activation Analysis). This particular study is part of a broader line of research, whose overall objective is to find the optimal procedure for analyzing the fluorite content of samples taken from different parts of a fluorite concentration plant, using the DGNAA method [1-2]. The mining sample is fluorspar, which contains other minerals in addition to fluorite, such as silica, barite, iron oxides and silicates. The main contribution of the article is the development of a new method for determining the fluorite content in minerals and the increase of sensitivity in respect to the symmetrical method and single-cycle activation.

Direct methods based on the origin-free modulus sum function (S) were first adapted in 1994 to the processing of intensity data from density functions with positive and negative scatterers. Nevertheless, that implementation used phase relationships explicitly with the inherent limitation introduced by the time consuming manipulation of quartets. This limitation was removed with the introduction of the S-FFT algorithm (maximising S with only Fourier transforms) and its posterior adaptation S₂-FFT for non-positive definite density functions. In the present work both algorithms are reformulated into a generalized one, thus simplifying their implementation in the XLENS® program. The resulting unified S-FFT algorithm is highly effective for crystal structures with at least one medium-heavy scatterer in the unit cell. We have successfully applied it on neutron diffraction data of compounds with negative Fermi lengths.

We illustrate the use of high-resolution neutron spectroscopy to explore the extreme spatial confinement of soft matter in nanostructured materials. Two well-defined limits are considered, involving either intercalation or interfacial adsorption of the ubiquitous polymer poly(ethylene oxide) in graphite-oxide-based hosts. Vibrational modes associated with the confined macromolecular phase undergo dramatic changes over a broad range of energy transfers, from those associated with intermolecular modes in the Terahertz frequency range (1 THz = 33 cm⁻¹), to those characteristic of strong chemical bonds above 2000 cm⁻¹. We also consider the effects of polymer chain size and chemical composition of the host material. Variation of the degree of oxidation and exfoliation of graphite oxide leads to two distinct cases, namely: (i) subnanometer two-dimensional confinement; and (ii) surface immobilization. Case (i) is characterised by significant changes to conformational and collective vibrational modes of the polymer as a consequence of a preferentially planar trans-trans-trans chain conformation, whereas case (ii) leads to a substantial increase in the population of gauche conformers. Macroscopically, case (i) translates into the complete suppression of crystallization and glassy behaviour. In contrast, case (ii) exhibits well-defined glass and melting transitions associated with the confined phase, yet at significantly lower temperatures than those of the bulk.

Micelles of the triblock copolymer Pluronic F127 can encapsulate drugs with various chemical structures and their architecture has been studied by small-angle neutron scattering (SANS). Interaction with a derivative of β-cyclodextrin, namely, heptakis(2,6-di-O- methyl)-β-cyclodextrin (DIMEB), induces a complete break-up of the micelles, providing a mechanism for drug release. In the presence of drugs partitioned within the micelles, competitive interactions between polymer, drug and cyclodextrin lead to a modulation of the micellar rupture, depending on the nature of the drug and the exact composition of the ternary system. These interactions can be further adjusted by temperature and pH. While the most widely accepted mechanism for the interaction between Pluronics and cyclodextrins is through polypseudorotaxane (PR) formation, involving the threading of β-CD on the polymer backbone, time-resolved SANS experiments show that de-micellisation takes place in less than 100 ms, thus unambiguously ruling out an inclusion complex between the cyclodextrin and the polymer chains.

We show that the combination of dielectric relaxation with neutron spin echo and incoherent neutron backscattering measurements performed in deuterated and protonated poly(ethylene terephthalate) suggests that the intrinsic dynamics of semicrystalline polymers occurs in an homogeneous scenario, similar to that valid to describe the dynamics of totally amorphous polymers. The quasielastic neutron scattering data are satisfactorily described by a theoretical model that considers that the proton mobility follows a random jump-diffusion in a restricted environment.

Poly(acrylic-acrylamide) interpenetrated microgels present continuous phase transition from collapsed to swollen state around 42 °C. The upper critical solution temperature (UCST) of this polymeric system has prompted scientists to consider them candidates for its use in biological applications such as smart drug delivery devices since the swelling of the polymer matrix would permit the release of the drug previously entrapped within the microgels. In these systems the increment of the temperature can break inter-chain interactions, mainly hydrogen bonds, which reduce the elastic tension that stabilizes the microgel, favoring the polymer swelling. The microgel molecular dynamics at the UCST can be investigated using Incoherent Elastic (IENS) and Quasielastic Neutron Scattering (IQNS). From the analysis of the IQNS data we obtained that the diffusion coefficient of the polymer segments depends on the composition of the interpenetrated matrix. Thus, at room temperature, microgels with a polymer composition of 50% of each component present a diffusion coefficient 1·10⁻¹² m²/s, while for the microgels formed by only one component the diffusion coefficient is 5.10⁻¹⁰ m²/s. This huge difference in the diffusion coefficient is conspicuously reduced when temperature increases, and we attribute this effect to the breaking of the inter-chain interaction. By means of FTIR-ATR analysis we have identified the groups that are involved in this phenomenon and we associate the breaking of the polyacrylic-polyacrylamide interactions with the swelling of the microgels.

We report on a quasielastic incoherent neutron scattering (QENS) experiment on liquid glycerol. QENS data were collected at the temperature T=380 K and with a resolution (FWHM) R=55μeV. The analysis of the quasielastic signal enables us to draw a consistent picture of the diffusive mechanism on a picosecond time scale and to compare with most recent models for glycerol dynamics. Model selection, performed with the fitting algorithm FABADA, gives us a preliminary description about the motions of the glycerol molecules in its liquid state.

The main objective of this paper is to present a method to fully determine the six degrees of freedom regarding position and orientation of a neighboring molecule around a central one, i.e. the g(r_CM,ω) distribution function. This is accomplished by completely determining the short range structure of liquid carbon tetrachloride, while employing results from two different methods, Molecular Dynamics (MD) [1] and Reverse Monte Carlo (RMC) [2]. Exclusively, the structural ordering of the first four molecules will be detailed.

The structure factor of deuterated liquid n-butanol (C₄D₁₀O) has been investigated by neutron diffraction with the aim of exploring the physical nature of the observed prepeak. The experiment was conducted using two neutron diffractometers: D16 to get a detailed structure factor in the low-Q range, and D4 for a high precision structure factor and proper normalization. In this way a total structure factor was determined covering an extended Q-range from 0.04 to 23.4 Å⁻¹. A molecular dynamics simulation using the general all-atom ab initio force field COMPASS was also carried out. The agreement between experimental and simulated data is very good, giving a plausible interpretation of the origin of the pre-peak observed at 0.6 Å⁻¹ as coming from the intermolecular ordering in the liquid.

Neutron polarized diffraction technique has been used to elucidate the magnetic moment distribution density in non stoichiometric Ni—Mn—Ga single crystals. These experiments allow us to determine a localized magnetic moment in the Mn position in the austenitic phase, and to validity qualitatively previous models of magnetic distributions where there are antiferromagnetic and ferromagnetic coupling for Mn atoms that are sited out of their properly positions. This measurements show the deep dependence of the magnetic moment with the composition and the atomic order.

Ni-Mn-Ga alloys show the highest magnetic-field-induced strain among ferromagnetic shape memory alloys. A great effort is being done in this alloy system to increase the application temperature range. In this sense, the addition of small amounts of Cobalt to NiMnGa alloys has been proved to increase the MT temperatures through the increase of the electron per atom relation (e/a). In this work, the analysis of the crystal structure of the present phases and the phase transformations has been performed on a Ni-Mn-Ga-Co alloy by neutron diffraction measurements from 10 K to 673 K. The study has been completed by means of calorimetric and magnetic measurements. On cooling the alloy undergoes a martensitic transformation from a face centered cubic structure to a nonmodulated tetragonal martensite. The appearance of intermartensite transformations can be disregarded in the whole temperature range below the martensitic transformation. However, a jump in the unit-cell volume of the tetragonal martensite has been observed at 325 K. Since this temperature is close to the Curie temperature of the alloy both, the structural and magnetic contributions are taken into account to explain the results.

The structural evolution of a Fe₇₀Cr₁₀B₂₀ metallic glass was followed by means of in situ high-temperature neutron thermo-diffraction and magnetization measurements. Above 723 K the crystallization of bcc-Fe together with a metastable (FeCr)₃B phase with tetragonal crystal structure (space group 1) is observed. Further heating gives rise to the transformation of the (FeCr)₃B phase into another tetragonal (FeCr)₂B phase (space group 14 / mcm) + bcc- Fe. On cooling down to room temperature no additional structural transformations occurred. This two-step crystallization process allows understanding quantitatively the intricate variation of the magnetization at high-temperature

Several pseudo-binary R_xR'_2-xFe₁₇ alloys (with R = Y, Ce, Pr, Gd and Dy) were synthesized with rhombohedral Th₂Zn₁₇-type crystal structure determined from x-ray and neutron powder diffraction. The choice of compositions was done with the aim of tuning the Curie temperature (T_C) in the 270 ± 20 K temperature range, in order to obtain the maximum magneto-caloric effect around room temperature. The investigated compounds exhibit broad isothermal magnetic entropy changes, ΔS_M(T), with moderate values of the refrigerant capacity, even though the values of ΔS_M^Peak are relatively low compared with those of the R₂Fe₁₇ compounds with R = Pr or Nd. The reduction on the ΔS_M^Peak is explained in terms of the diminution in the saturation magnetization value. Furthermore, the ΔS_M(T) curves exhibit a similar caret-like behavior, suggesting that the magneto-caloric effect is mainly governed by the Fe-sublattice. A single master curve for ΔS_M/ΔS_M^Peak(T) under different values of the magnetic field change are obtained for each compound by rescaling of the temperature axis.

We report measurements of DC (AC) magnetic susceptibility and neutron diffraction on TbNiAl₂ alloy. The Rietveld refinements of the x-ray and neutron diffraction data are consistent with an orthorhombic structure of the type MgCuAl₂ (space group Cmcm). The results of DC (AC)- magnetic susceptibility show two successive magnetic transitions at 20 K and 11.7 K with antiferromagnetic and ferromagnetic (or ferrimagnetic) features, respectively. On the other hand, neutron diffraction patterns show that, below 20 K and down to 12 K, new reflexions appear, confirming the antiferromagnetic character of the transition observed in the macroscopic measurements. Also, at least one of these new reflexions, located at Q = 1.2 Å⁻¹, shifts to higher angles when the temperature decreases, indicating an incommensurate magnetic structure. Below 11 K, many reflexions disappear and new reflexions increase, evidencing a new magnetic transition.

Neutron diffraction data of DyCrO₄ oxide, prepared at 4 GPa and 833 K from the ambient pressure zircon-type, reveal that crystallize with the scheelite-type structure, space group I4₁/a. Accompanying this structural phase transition induced by pressure the magnetic properties change dramatically from ferromagnetism in the case of zircon to antiferromagnetism for the scheelite polymorph with a T_N = 19 K. The analysis of the neutron diffraction data obtained at 1.2 K has been used to determine the magnetic structure of this DyCrO₄-scheelite oxide which can be described with a k = [0, 0, 0] as propagation vector, where the Dy and Cr moments are lying in the ab-plane of the scheelite structure. The ordered magnetic moments are 10 μB and 1μB for Dy⁺³ and Cr⁺⁵ respectively.

Polycrystalline oxygen-stoichiometric LaCo_0.5Ti_0.5O₃ perovskite oxide has been prepared by soft-chemistry procedures followed by annealing in air at 800°C. A new reduced LaCo_0.5Ti_0.5O_3-δ specimen has been obtained by topotactical oxygen removal in an H2/N2 (5%/95%) flow at 600°C. The structural characterization has been conducted from neutron powder diffraction (NPD) data, very sensitive to the contrast between Co and Ti and the oxygen stoichiometry. Both perovskites (oxidized and reduced) crystallize in the orthorhombic Pbnm, space group. The partial reduction of Ti⁴⁺ to Ti³⁺ in the reduced phase is accompanied with the occurrence of oxygen vacancies, located at the axial octahedral sites, and it is expected to support the ionic conductivity, as usually observed in oxygen-defective perovskites. Thermogravimetric analysis (TGA) substantiates the oxygen stoichiometry and the stability range of the reduced sample. All the samples in study display a semiconductor-like behavior with values that not reach below to 0.5 Scm⁻¹ for all the phases. Moreover, the measured thermal expansion coefficients perfectly match with the values usually displayed by SOFC electrolytes.

In this paper we describe some novel members of the RNiO₃ perovskites, containing Ni³⁺ and presenting metal-insulator transitions coupled to a charge disproportionation effect. This phenomenon is observed in the insulating state as a subtle monoclinic distortion, due to the presence of two unequivalent Ni ions with different coordination environments, corresponding to expanded and contracted octahedra alternating in the three-dimensional network. Here we examine how the introduction of mixed rare-earth cations at the R sublattice affects the metal-insulator transition and the structural features, from high resolution neutron powder diffraction studies.

The thermal evolution of the CaIrO₃ post-perovskite structure has been determined by neutron powder diffraction (time-of-flight) measurements in a wide temperature range, from 1.8K to 550K. The linear expansion is similar to that found in previous x-ray diffraction studies, being α_b > α_c > α_a,. However, the difference in relative lattice parameters is less pronounced in the present case, suggesting a more isotropic evolution under temperature. Other structural differences found at low and high temperatures through several X-ray and neutron diffraction studies have been also analysed.

Chemical and magnetic structure modulations in antimony vanadium mixed oxide with composition Sb_0.92V_1.08O₄ prepared in reducing conditions are studied using diffraction techniques, mainly nuclear and magnetic neutron scattering, electron and X-ray powder diffraction. Magnetic susceptibility measurements show possible magnetic order of V³⁺ magnetic moments that is confirmed with neutron diffraction at T_N ~50K. The average commensurate nuclear cell belongs to the tetragonal rutile structural type with cell constants: a=4.6066(11)Å and c=3.0812(8)Å at 60K. However the nature of the magnetic structure is incommensurate with propagation vector k= [0, 0, ± 0.266(1)] related to short range order phenomena and V-Sb alternating occupancy along the crystallographic c-axis.

Calcination of a co-doped (N-C-S) TiO₂ photocatalyst has been done following the whole process by neutron diffraction (instrument D1B of the ILL) with the objective of study the transition between two crystalline phases: anatase and rutile in order to find the optimum temperature leading to the coexistence of both for this catalyst whose band gap has been shifted to give activity in the visible part of the electromagnetic spectrum. This coexistence is important as it has been established that these catalyst are more efficient than those having only one individual phase. At this respect, it is very important to find the optimum temperature at with synthesis has to be done. In this research it was established that at the heating ramp of 17°C/5 min, the coexistence of both crystalline phases took place within a narrow margin of temperatures between 610°C and 690°C. At higher temperatures only rutile can be identified as the crystalline phase of the TiO₂.

Residual strain profiles were measured by neutron diffraction in alumina-aluminum titanate ceramic composites sintered at two different temperatures, namely 1450 and 1550°C. The results show that irrespective of the direction and the sintering temperature, the obtained profiles are almost flat, with very similar results for both temperatures. In addition, the results demonstrate that the alumina is in compression whereas the aluminium titanate is subjected to tensile residual stresses.

Cementitious materials are much more complex than it seems at a first sight. On one hand, due to the excess of water needed to make the mix workable, a network of pores is generated, that puts in contact the material with the environment and allows their attack by aggressive agents that can be physical of chemical agents, producing the deterioration of the concrete itself and corrosion of the rebars. Then, it is necessary to study the transport properties and the chemical and physical interaction of aggressive agents with the solid and liquid phases of the cement paste the corrosion of the rebars, and the reparation processes. This is an approach concerning the service life of structures, however, we cannot forget an important chapter which is gaining much relevance in the last time: that of the special uses of concrete, for which, tailored concretes have to be designed. In order to undertake these problems, we need new analysis tools, different that the traditionally ones applied to study concrete, that allows the understanding of the mechanisms regulating the processes. One of these analysis tools is neutron diffraction that gives us the possibility of study the bulk of materials using a quite big specimen. In this work, 4 different problems undertaken with the help of neutrons in experiments carried out by the group of the author at the ILL, at the D1B and D20 instruments are presented.