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Thin film layer-by-layer room-temperature synthesis of targeted DUT-8 MOFs from 2,6-ndc and dabco ligands give different crystalline framework growths depending on the metal cation used: Cu(2,6-ndc) and Zn(2,6-ndc)(H2O).

The outstanding diversity of Zr-based frameworks is inherently linked to the variable coordination geometry of Zr-oxo clusters and the conformational flexibility of the linker, both of which allow for different framework topologies based on the same linker–cluster combination. In addition, intrinsic structural disorder provides a largely unexplored handle to further expand the accessibility of novel metal–organic frameworks (MOFs) structures that can be formed. In this work we report the concomitant synthesis of three topologically different MOFs based on the same M6O4(OH)4 clusters (M = Zr or Hf) and methane-tetrakis(p-biphenyl-carboxylate) (MTBC) linkers. Two novel structural models are presented based on single crystal diffraction analysis, namely cubic c (4,12)MTBC-M6 and trigonal tr (4,12)MTBC-M6, which comprise 12-coordinated clusters and 4 coordinated tetrahedral linkers. Notably, the cubic phase features a new architecture based on orientational cluster disorder, which is essential for its formation and has been analyzed by a combination of average structure refinements and diffuse scattering analysis from both powder and single crystal X-ray diffraction data. The trigonal phase also features structure disorder, although involving both linkers and secondary building units. In both phases, remarkable geometrical distortion of the MTBC linkers illustrates how linker flexibility is also essential for their formation and expands the range of achievable topologies in Zr-based MOFs and its analogues.

The design and discovery of three-dimensional crystalline metal–organic frameworks (MOFs) from linkers with phosphonate coordinating groups and even alkaline earth metals is largely undeveloped. Herein, we report a strategy for realizing new, stable, and robust barium phosphonate MOFs, termed Empa-1 and Empa-2. The two-dimensional (2D) Empa-1 or three-dimensional (3D) Empa-2 could be realized by way of systematically modulating the ratio of Ba2+ with a tetratopic phosphonate-based linker that was crafted to incorporate nitrogen-rich triazine units bridged by a fixed piperazine core. In addition to this synthetic approach, temperature-dependent synchrotron-radiation powder X-ray diffraction analysis demonstrated that the 2D Empa-1 undergoes an irreversible phase transition upon heating and subsequent dehydration to form the 3D Empa-2. Given the presence of uncoordinated phosphonic acid moieties within the structure of 3D Empa-2, the CO2 sorption capabilities are reported. We believe our ability to link the alkaline earth metal barium with a novel tetratopic phosphonate linker, as evidenced by the robust structures of Empa-1 and -2, paves the way for further exploration and discovery of new crystalline, porous frameworks with greater structural diversity, stability, and wide-scale practical applicability.

Many functional materials are today synthesised in form of nanoparticles displaying preferred orientation effects to some small or large extent. The analysis of diffraction data of such kind of systems is best performed in the framework of the total scattering approach that prescinds from translation symmetry assumptions. We therefore derived modified expressions for the most common total scattering functions, in particular the Debye Scattering Equation (DSE) that yields the texture-averaged differential cross section as a function of atomic coordinates and texture parameters. The modified DSE encodes higher-order even spherical Bessel functions which account for the texture effect. Selection rules arising from experimental geometries and symmetries are discussed. In addition the duality of the texture effect is introduced showing the effects of texture on both the I(Q) and G(r). The paper includes several definitions and appendices which are meant to be useful for those involved in the development of crystallographic computing., 46 pages, 8 figures, 2 tables, 7 sections, 2 appendices

The conventional strategy of synthetic colloidal chemistry for bright and stable quantum dots has been the production of epitaxially matched core/shell heterostructures to mitigate the presence of deep trap states. This mindset has been shown to be incompatible with lead halide perovskite nanocrystals (LHP NCs) due to their dynamic surface and low melting point. Nevertheless, enhancements to their chemical stability are still in great demand for the deployment of LHP NCs in light-emitting devices. Rather than contend with their attributes, we propose a method in which we can utilize their dynamic, ionic lattice and uniquely defect-tolerant band structure to prepare non-epitaxial salt-shelled heterostructures that are able to stabilize these materials against their environment, while maintaining their excellent optical properties and increasing scattering to improve out-coupling efficiency. To do so, anchored LHP NCs are first synthesized through the heterogeneous nucleation of LHPs onto the surface of microcrystalline carriers, such as alkali halides. This first step stabilizes the LHP NCs against further merging, and this allows them to be coated with an additional inorganic shell through the surface-mediated reaction of amphiphilic Na and Br precursors in apolar media. These inorganically shelled NC@carrier composites offer significantly improved chemical stability toward polar organic solvents, such as γ-butyrolactone, acetonitrile, N-methylpyrrolidone, and trimethylamine, demonstrate high thermal stability with photoluminescence intensity reversibly dropping by no more than 40% at temperatures up to 120 °C, and improve compatibility with various UV-curable resins. This mindset for LHP NCs creates opportunities for their successful integration into next-generation light-emitting devices., ACS Nano, 13 (10), ISSN:1936-0851, ISSN:1936-086X

A simple method is reported for the preparation of silver nanoparticle (AgNP) embedded pH-responsive hydrogel microparticle catalyst via Michael addition gelation and in-situ silver nitrate (AgNO3) reduction. The AgNP-hydrogel microsphere exhibited an efficient reduction of pollutants like 4-Nitrophenol (4-NP) and Congo red (CR) under acidic medium with turn over frequency (TOF) of ~170 h–1 and ~124 h–1 respectively. Interestingly, the activity of the catalysts was turned-OFF under a basic medium (≥ pH 12) due to the deswelling pH-responsive matrix surrounding the AgNPs. On the contrary, turning-OFF the hydrogenation of a cationic pollutant like methylene blue (MB) using high pH (≥ 12) was not possible, due to ionic interaction of MB molecules with the negatively charged catalyst at this pH. This feature was used to demonstrate selective hydrogenation of only MB from a mixture of 4-NP and MB. Finally, five recycling steps confirmed the reusability and practical application potential of the catalyst.

For the first time, a high-density amorphous and crack-free bulk metallic glass (BMG) based on a precious metal (PdCuNiP) was produced via additive manufacturing (AM). Laser powder-bed fusion (LPBF) was used for the fabrication of the samples, and led to a density of 99.6%. Excellent mechanical properties such as high hardness and compressive strength were achieved, overcoming the limitations usually found for precious metals in jewelry and watchmaking. Furthermore, without any post-processing, a mirror-like smooth and brilliant surface was directly obtained, which is highly beneficial for applications where surface finish or aesthetics matters. The effect of the main processing parameters, such as laser power and laser-scanning speed, on the shape of single tracks was investigated by laser confocal microscopy (LCM). Following the single-track experiments, highly amorphous LPBF samples were produced. The samples were characterized by optical microscopy (OM), scanning electron microscopy (SEM), conventional and synchrotron X-ray diffraction (XRD), micro-computed tomography (μ-CT), compression tests, and microhardness. The crystallization kinetics of the powder alloy was investigated via fast differential scanning calorimetry (FDSC). A small quantity of the powder (< 70 g) was used for the fabrication of samples, alleviating the cost of the process. Efficient production of precious metal parts with enhanced mechanical properties is demonstrated., Applied Materials Today, 24, ISSN:2352-9407

We present an extension and revision of the spectroscopic and structural data of the mixed-stack charge-transfer (CT) crystal 3,3′,5,5′-tetramethylbenzidine–tetrafluorotetracyanoquinodimethane (TMB–TCNQF4), associated with new electric and dielectric measurements. Refinement of synchrotron structural data at low temperature has led to revise the previously reported C2/m structure. The revised structure is P21/m, with two dimerized stacks per unit cell, and is consistent with the low-temperature vibrational data. However, polarized Raman data in the low-frequency region also indicate that by increasing temperature above 200 K, the structure presents an increasing degree of disorder, mainly along the stack axis. X-ray diffraction data at room temperature have confirmed that the correct structure is P21/m─no phase transitions─but did not allow substantiating the presence of disorder. On the other hand, dielectric measurements have evidenced a typical relaxor ferroelectric behavior already at room temperature, with a peak in the real part of dielectric constant ϵ′(T,ν) around 200 K and 0.1 Hz. The relaxor behavior is explained in terms of the presence of spin solitons separating domains of opposite polarity that yield to ferroelectric nanodomains. TMB–TCNQF4 is confirmed to be a narrow-gap band semiconductor (Ea ∼ 0.3 eV) with a room-temperature conductivity of ∼10–4 Ω–1 cm–1., A.G. thanks Prof. Pascale Foury-Leylekian for very helpful discussions about the crystallographic issues. R.F. thanks Prof. Anthony Linden for his help in the X-ray diffraction data collection. J.K.H.F. and P.L. acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG) via the Transregional Collaborative Research Center TRR80 (Augsburg, Munich). R.P. and M.M.-T. acknowledge support from the Marie Curie Cofund, Beatriu de Pinós Fellowships (Grant nos. AGAUR 2017 BP 00064). This work was also supported by the Spanish Ministry project GENESIS PID2019-111682RB-I00, the “Severo Ochoa” Programme for Centers of Excellence in R&D (FUNFUTURE, CEX2019-000917-S), and the Generalitat de Catalunya (2017-SGR-918). The Elettra Synchrotron (CNR Trieste) is acknowledged for granting the beamtime at the single-crystal diffraction beamline XRD1 (Proposal ID 20185483). In Parma, the work has benefited from the equipment and support of the COMP-HUB Initiative, funded by the “Departments of Excellence” program of the Italian Ministry for Education, University and Research (MIUR, 2018-2022).

New polyhydroxyoctanoate based composites with incorporated TiO2 microfibers were produced. The presence of the inorganic constituent influenced morphology, physical properties and functionality of the obtained biomaterials. The degree of PHO crystallinity decreased in the composites in a TiO2 concentration dependent manner. The composites were stiffer than the neat PHO, however they preserved their flexibility. Biocompatibility and cellular migration studies showed that composites support cell viability and migration. The obtained results suggest that PHO/TiO2 composites could be used as novel biomaterials with tunable properties for biomedical applications. Supplementary material: [https://cherry.chem.bg.ac.rs/handle/123456789/4439]

Silicon nanowire-based sensors find many applications in micro- and nano-electromechanical systems, thanks to their unique characteristics of flexibility and strength that emerge at the nanoscale. This work is the first study of this class of micro- and nano-fabricated silicon-based structures adopting the scanning X-ray diffraction microscopy technique for mapping the in-plane crystalline strain (epsilon(044)) and tilt of a device which includes pillars with suspended nanowires on a substrate. It is shown how the micro- and nanostructures of this new type of nanowire system are influenced by critical steps of the fabrication process, such as electron-beam lithography and deep reactive ion etching. X-ray analysis performed on the 044 reflection shows a very low level of lattice strain (, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (FWF)

A multiscale analytical approach is presented for understanding the structure of micro- and nano-fabricated nanowire-based sensors. Using scanning X-ray diffraction microscopy, crystal deformation is evaluated with respect to lattice strain and tilt caused by the manufacturing process of a silicon monolith., Silicon nanowire-based sensors find many applications in micro- and nano-electromechanical systems, thanks to their unique characteristics of flexibility and strength that emerge at the nanoscale. This work is the first study of this class of micro- and nano-fabricated silicon-based structures adopting the scanning X-ray diffraction microscopy technique for mapping the in-plane crystalline strain (∊044) and tilt of a device which includes pillars with suspended nanowires on a substrate. It is shown how the micro- and nanostructures of this new type of nanowire system are influenced by critical steps of the fabrication process, such as electron-beam lithography and deep reactive ion etching. X-ray analysis performed on the 044 reflection shows a very low level of lattice strain (

A simple one-step solventless in-situ reduction method was developed to prepare silver nanoparticle (AgNP) based polymer composites using different silver precursors and thermoplastic polymers. This method utilizes the mild reducing environment of thermoplastic polymer melts to convert silver precursors to AgNPs during the extrusion process. Complete reduction of Ag2O with broad AgNP size distribution (20 ± 18 nm) in polyamide 6 (PA6) was obtained after 5 min processing. For same matrix, the uniformity of AgNPs improved significantly after 10 min processing time, associated with a slight increase in the particle diameter (26 ± 9 nm). No significant impact of in-situ AgNP synthesis method on chemical and macromolecular characteristics of polyamide 6 was detected. When this method was used to synthesize AgNPs in polylactic acid and polypropylene, the influence of surface energy of polymer melt was evident. Reduction of Ag2O in polylactic acid (at 165 °C) was slower compared to PA6 and 95 ± 3% Ag2O reduction was achieved after 10 min of processing. When polypropylene was used as the matrix, only 60% reduction of Ag2O was achieved, possibly due to poor wetting of the silver precursor, owing to the low surface energy of polypropylene. AgNP-PA6 composites were also successfully prepared using Ag2CO3 and Ag-palmitate as precursors. To demonstrate the potential application of such composites in food packaging, the silver release and antibacterial activity of AgNP-PA6 composite were also studied. Though the composites released 500 times less silver compared to the permitted limits of different safety standards, they exhibited an excellent antibacterial activity against a typical food pathogen (Listeria monocytogenes) already at a low level of AgNP loading i.e. 0.5 wt%.

We present our investigation on the crystallization of IBS HfO2 on (0001) SiO2. The crystallization was studied by in-situ XRD. The activation energy was 2.6±0.5 eV. The growth follows a two-dimensional mode. LIDT measurements (5000-on-1) with 10 ns pulses at 355 nm on 3QWT HfO2 layers shows that the crystallization leads to increase of the laser irradiation resistance. The 0%-LIDT of the as coated sample was 3.1 J/cm2 and increased to 3.7 J/cm2 after 5h @ 500°C.

The new release ofDEBUSSYis introduced, a free open-source package devoted to the application of the Debye function analysis of powder diffraction data from nanocrystalline, defective and/or nonperiodic materials. The general strategy of the suite remains unchanged, following a two-step approach managed by theCLAUDEandDEBUSSYprograms, respectively. The first step essentially consists in generating a database where structural, size and shape information on a nanocrystal population is stored; the second step consists in the calculation, through the Debye scattering equation, of the total diffraction pattern using the previously generated database and a set of model parameters provided by the user and then optimized by the program. The novelties lie in the computational, modelling and graphical levels, and several new programs and features have been added. Among these are a new general comprehensive input file format (.ddb) for the database generation, the automatic management of the space-group symmetry and .cif file, new nanocrystal shapes, size-dependent site occupancy factors and thermal parameters for each atomic species, new lattice expansion functions, and a newly developed algorithm for calculating the standard errors of the optimized parameters. TheCLAUDEsuite also includes a program for calculation of the pair distribution function. Last but not least, a graphical user interface, which makes it easier to edit input files, execute the programs of the suite in a chain-like way, and plot the results in an automatic or custom manner, is provided.

The crystallization kinetics of amorphous 3 and 8 mol% yttria stabilized zirconia (3YSZ and 8YSZ) thin films grown by pulsed laser deposition (PLD), spray pyrolysis and dc-magnetron sputtering are explored. The deposited films were heat treated up to 1000 °C ex situ and in situ in an X-ray diffractometer. A minimum temperature of 275 °C was determined at which as-deposited amorphous PLD grown 3YSZ films fully crystallize within five hours. Above 325 °C these films transform nearly instantaneously with a high degree of micro-strain when crystallized below 500 °C. In these films the t′′ phase crystallizes which transforms at T > 600 °C to the t′ phase upon relaxation of the micro-strain. Furthermore, the crystallization of 8YSZ thin films grown by PLD, spray pyrolysis and dc-sputtering are characterized by in situ XRD measurements. At a constant heating rate of 2.4 K min−1 crystallization is accomplished after reaching 800 °C, while PLD grown thin films were completely crystallized already at ca. 300 °C.

The crystallization upon thermal treatment of 8 mol% yttria-stabilized zirconia thin films deposited by RF-sputtering at room temperature is investigated. The as-deposited YSZ films are biphasic with crystallites of 5–10 nm in diameter building a columnar-like microstructure. Fully crystalline YSZ thin films are obtained after isothermal dwells in the temperature range 800–1100 °C. X-ray diffraction and Raman spectroscopy demonstrate that the crystalline films have a cubic structure retained even after high-temperature annealing while a strong texture is developed. Further, a stagnating grain-growth is observed, characterized by a final grain size of about 60 nm and a micro-strain of 0.15%. Given the observed films' micro-structural stability, their application in miniaturized electrochemical devices such as micro-solid oxide fuel cells or sensors can be foreseen.

Size and shape tunability and low-cost solution processability make colloidal lead chalcogenide quantum dots (QDs) an emerging class of building blocks for innovative photovoltaic, thermoelectric and optoelectronic devices. Lead chalcogenide QDs are known to crystallize in the rock-salt structure, although with very different atomic order and stoichiometry in the core and surface regions; however, there exists no convincing prior identification of how extreme downsizing and surface-induced ligand effects influence structural distortion. Using forefront X-ray scattering techniques and density functional theory calculations, here we have identified that, at sizes below 8 nm, PbS and PbSe QDs undergo a lattice distortion with displacement of the Pb sublattice, driven by ligand-induced tensile strain. The resulting permanent electric dipoles may have implications on the oriented attachment of these QDs. Evidence is found for a Pb-deficient core and, in the as-synthesized QDs, for a rhombic dodecahedral shape with nonpolar {110} facets. On varying the nature of the surface ligands, differences in lattice strains are found.

We discuss here what important knowledge can be gained by X-ray diffraction (of course, more specifically, we talk of X-ray powder diffraction) experiments on nanoparticles and nanomaterials in general. Historically, the uses of X-ray diffraction have been to investigate (a) the crystal structure of materials at the atomic scale and (b) their microstructure, a broad term meaning deviations from perfect crystalline order on a scale that is larger than the atomic one but still microscopic. In fact, macroscopic properties of materials tend to depend on both of those. For nanomaterials, the focus is to understand how the small crystal domain extension and related phenomena influence properties that differ – often in a very useful way – from the parent crystalline material. This means that the focus is on the microstructure, due to the fact that reduced domain extension is a (strong) deviation from crystal order – this is by definition something that extends to infinity. Of course there exist crystalline phases that are stable only at the nanoscale – and in such case, the crystal structure determination still is very important. In this contribution, we shall review all modern experimental methods and especially – as this is the core of the method – the data analysis techniques currently used, from the oldest, based on the Bragg formalism to interpret crystal diffraction, to the newest, relying on atomic-scale modeling.

Knowledge about the crystallization and grain growth characteristics of metal oxide thin films is essential for effective microstructural engineering by thermal post-annealing and the integration to Si-based miniaturized electroceramic devices. Finite size and interface effects may cause fundamentally different behavior compared to three dimensional macroscopic systems. This work presents a comprehensive investigation of the crystallization kinetics and microstructural evolution upon thermal post-annealing of amorphous 200 nm and 1.2 μm thin films of 8 mol% yttria-stabilized zirconia grown by pulsed laser deposition (PLD) using ex- and in-situ X-ray diffraction, Raman spectroscopy, and electron microscopy techniques. The layers exhibit a remarkably low crystallization temperature of 200–250 °C while exposure to energetic electrons induces the formation of randomly dispersed ~ 20 nm sized crystallites already at ambient temperature. The isothermal amorphous to crystalline phase transformation kinetics can be described quantitatively by the Johnson–Mehl–Avrami–Kolmogorov model. They reveal characteristics of a three dimensional growth under cation bulk diffusion control with heterogeneous nucleation that changes from continuous to instantaneous initial seeding at temperatures above 300 °C. Large (> 100 nm) equiaxed grains are formed rapidly without a stabilization of transient nanocrystals during the thermally induced phase transformation. A stagnation of normal grain growth resulting in a logarithmic normal size distribution is observed once the average grain dimensions approach the film thickness. The results on the crystallization and grain growth of the PLD-grown YSZ films are evaluated with regards to the fabrication of YSZ solid electrolyte membranes for Si-supported micro solid oxide fuel cells and gas sensors.

One of the main technical concerns of Megawatt-class spallation neutron sources is the removal of the heat deposited in the target station. A way to overcome it is to use targets consisting of flowing liquid metals, but the already tested materials – mercury and lead–bismuth eutectic (LBE) – are not unproblematic. We show here that another eutectic alloy containing lead and gold (LGE) could be a suitable alternative. Besides a chemical toxicity lower than mercury, this low melting-point alloy has the advantage of being solid at RT. Moreover, it combines a neutron production similar to mercury and LBE with smaller amounts of alpha-emitting nuclides, relieving safety and environmental requirements. Further advantages are a reduced decay heat a few weeks after stopping operation and density variations in the solid state significantly smaller than LBE. Steel corrosion appears to be more important than expected but if it remains manageable, the current research suggests that LGE could be a valuable alternative to LBE and mercury.

Bio-inspired apatite nanoparticles precipitated in the presence of citrate ions at increasing maturation times are characterized in terms of structure, size, morphology, and composition through advanced X-ray total scattering techniques. The origin of the platy crystal morphology, breaking the hexagonal symmetry, and the role of citrate ions is explored. By cross-coupling the size and shape information of crystal domains with those obtained by atomic force microscopy on multidomain nanoparticles, a plausible mechanism underlying the amorphous-to-crystal transformation is reconstructed. In the present study, citrate plays the distinct roles of inducing the platy morphology of the amorphous precursor and controlling the thickness of the Ca-deficient apatite nanocrystals. These findings can open new scenarios also in bone mineralization, where citrate might have a broader role to play than has been thought to date.

The size-driven expansion and oxidation-driven contraction phenomena of nonstoichiometric magnetite–maghemite core–shell nanoparticles have been investigated by the total scattering Debye function approach. Results from a large set of samples are discussed in terms of significant effects on the sample average lattice parameter and on the possibility of deriving the sample average oxidation level from accurate, diffraction-based, cell values. Controlling subtle experimental effects affecting the measurement of diffraction angles and correcting for extra-sample scattering contributions to the pattern intensity are crucial issues for accurately estimating lattice parameters and cation vacancies. The average nanoparticle stoichiometry appears to be controlled mainly by iron depletion of octahedral sites. A simple law with a single adjustable parameter, well correlating lattice parameter, stoichiometry and size effects of all the nanoparticles present in the whole set of samples used in this study, is proposed.

Total Scattering Methods are nowadays widely used for the characterization of defective and nanosized materials. They commonly rely on highly accurate neutron and synchrotron diffraction data collected at dedicated beamlines. Here, we compare the results obtained on conventional laboratory equipment and synchrotron radiation when adopting the Debye Function Analysis method on a simple nanocrystalline material (a synthetic iron oxide with average particle size near to 10 nm). Such comparison, which includes the cubic lattice parameter, the sample stoichiometry and the microstructural (size-distribution) analyses, highlights the limitations, but also some strengthening points, of dealing with conventional powder diffraction data collections on nanocrystalline materials.

The important source of interface conductivity in LaAlO3/SrTiO3 heterostructures, the Ti 3d carriers, is probed with resonant inelastic x-ray scattering at the Ti 2p(3/2) edge of epitaxially grown superlattices. We reveal unambiguously the generation of both localized and delocalized Ti 3d carriers as a result of the built-up heterointerface. Furthermore, we determine that the interface Ti3+O6 octahedra are orthorhombically distorted and quantify the crystal-field splitting energies. We argue that for as-grown superlattices, both types of Ti 3d carriers originate mainly from oxygen vacancies, whereas for fully oxidized samples they result from electronic reconstruction.

Iron oxide nanoparticles (NPs) show different structures as a function of oxidation state. In particular, magnetite (Fe3O4) NPs are easily oxidized in air at moderate temperatures, eventually yielding maghemite (Fe2O3). Oxidation proceeds via the creation of iron vacancies. While the vacancies may be created with a random distribution throughout the octahedral Fe sites, they eventually order over a specific subset of these sites, lowering the symmetry from F-centered (magnetite) to P-centered (cubic maghemite). By ex situ X-ray Total Scattering studies of magnetite-maghemite NPs in different oxidation states[1] we have recently studied, by the DFA method[2], the correlation between particle diameter, stoichiometry and lattice parameter in polydisperse NP samples unraveling also the size dependence of lattice parameter and composition. Moreover, we have shown indirect evidence of the formation of a polycrystalline surface layer of maghemite on a magnetite core in the intermediate oxidation states. Motivated by the excellent ex-situ results, we have also performed in-situ studies where magnetite NPs were oxidised in air at moderate temperatures (50-200 C). We present here an in-situ study performed at the X04SA-Materials Science beamline of the Swiss Light Source synchrotron[3]. Total Scattering X-ray diffraction patterns were collected every few minutes, while the oxidation was completed within several hours. The mechanism of NPs oxidation - whereas a surface oxidised layer is formed by outwards diffusion of Fe, then the vacancies so created order themselves giving rise to the maghemite-magnetite phase transition, will be examined in great detail. We will discuss, on robust statistical basis, the calculation of kinetic and diffusion constants, the temperature effect on the lattice constant and on the thickness of the surface oxidised layer; the different possible structural models for the cubic-maghemite NPs. We thank for support Fondazione Cariplo (2009-0289).