Structural Features of the Fragments from Cast Iron Cauldrons of the Medieval Golden Horde: Neutron Tomography Data.

The spatial arrangement of the internal pores inside several fragments of ancient cast iron cauldrons related to the medieval Golden Horde period was studied using the neutron tomography method. The high neutron penetration into a cast iron material provides sufficient data for detailed analysis of the three-dimensional imaging data. The size, elongation, and orientation distributions of the observed internal pores were obtained. As discussed, the imaging and quantitative analytical data are considered structural markers for the location of cast iron foundries, as well as a feature of the medieval casting process.

Structural, Magnetic and Vibrational Properties of Van Der Waals Ferromagnet CrBr3 at High Pressure.

The crystal and magnetic structures of van der Waals layered ferromagnet CrBr3 were studied using X-ray powder diffraction and neutron powder diffraction at pressures up to 23 GPa at ambient temperature and up to 2.8 GPa in the temperature range 6-300 K, respectively. The vibration spectra of CrBr3 were studied using Raman spectroscopy at pressures up to 23 GPa at ambient temperature. The anomalous pressure behavior of structural parameters and vibrational modes was observed, associated with a gradual isostructural phase transition in the pressure range 2.5-7 GPa. The Curie temperature TC reduced rapidly with a pressure coefficient dTC/dP=-4.1(4) K/GPa. A full suppression of the ferromagnetic state was expected at PC~8.4 GPa, where onset of the antiferromagnetic spin arrangement or magnetically disordered state may take place. Anomalies in Raman spectra at P~15 GPa point to another possible phase transformation in CrBr3, which may be related to the proximity of metallization of this van der Waals ferromagnet.

High Pressure-Driven Magnetic Disorder and Structural Transformation in Fe3 GeTe2 : Emergence of a Magnetic Quantum Critical Point.

Among the recently discovered 2D intrinsic van der Waals (vdW) magnets, Fe3 GeTe2 (FGT) has emerged as a strong candidate for spintronics applications, due to its high Curie temperature (130 - 220 K) and magnetic tunability in response to external stimuli (electrical field, light, strain). Theory predicts that the magnetism of FGT can be significantly modulated by an external strain. However, experimental evidence is needed to validate this prediction and understand the underlying mechanism of strain-mediated vdW magnetism in this system. Here, the effects of pressure (0 - 20 GPa) are elucidated on the magnetic and structural properties of Fe3 GeTe2 by means of synchrotron Mössbauer source spectroscopy, X-ray powder diffraction and Raman spectroscopy over a wide temperature range of 10 - 290 K. A strong suppression of ferromagnetic ordering is observed with increasing pressure, and a paramagnetic ground state emerges when pressure exceeds a critical value, PPM ≈ 15 GPa. The anomalous pressure dependence of structural parameters and vibrational modes is observed at PC ≈ 7 GPa and attributed to an isostructural phase transformation. Density functional theory calculations complement these experimental findings. This study highlights pressure as a driving force for magnetic quantum criticality in layered vdW magnetic systems.

Pore Segmentation Techniques for Low-Resolution Data: Application to the Neutron Tomography Data of Cement Materials.

The development of neutron imaging facilities provides a growing range of applications in different research fields. The significance of the obtained structural information, among others, depends on the reliability of phase segmentation. We focused on the problem of pore segmentation in low-resolution images and tomography data, taking into consideration possible image corruption in the neutron tomography experiment. Two pore segmentation techniques are proposed. They are the binarization of the enhanced contrast data using the global threshold, and the segmentation using the modified watershed technique-local threshold by watershed. The proposed techniques were compared with a conventional marker-based watershed on the test images simulating low-quality tomography data and on the neutron tomography data of the samples of magnesium potassium phosphate cement (MKP). The obtained results demonstrate the advantages of the proposed techniques over the conventional watershed-based approach.

Neutron Tomography Studies of Two Lamprophyre Dike Samples: 3D Data Analysis for the Characterization of Rock Fabric.

The rock fabric of two lamprophyre dike samples from the Koy-Tash granitoid intrusion (Koy-Tash, Jizzakh region, Uzbekistan) has been studied, using the neutron tomography method. We have performed virtual segmentation of the reconstructed 3D model of the tabular igneous intrusion and the corresponding determination of dike margins orientation. Spatial distributions of inclusions in the dike volume, as well as further analysis of size distributions and shape orientations of inclusions, have been obtained. The observed shape preferred orientations of inclusions as evidence of the magma flow-related fabric. The obtained structural data have been discussed in the frame of the models of rigid particle motion and the straining of vesicles in a moving viscous fluid.

Phase Composition and Its Spatial Distribution in Antique Copper Coins: Neutron Tomography and Diffraction Studies.

The chemical and elementary composition, internal arrangement, and spatial distribution of the components of ancient Greek copper coins were studied using XRF analysis, neutron diffraction and neutron tomography methods. The studied coins are interesting from a historical and cultural point of view, as they are "Charon's obol's". These coins were discovered at the location of an ancient Greek settlement during archaeological excavations on the "Volna-1" necropolis in Krasnodar Region, Russian Federation. It was determined that the coins are mainly made of a bronze alloy, a tin content that falls in the range of 1.1(2)-7.9(3) wt.%. All coins are highly degraded; corrosion and patina areas occupy volumes from ~27 % to ~62 % of the original coin volumes. The neutron tomography method not only provided 3D data of the spatial distribution of the bronze alloy and the patina with corrosion contamination inside coin volumes, but also restored the minting pattern of several studied coins. Taking into account the obtained results, the origin and use of these coins in the light of historical and economic processes of the Bosporan Kingdom are discussed.

The structure of scleractinian coral skeleton analyzed by neutron diffraction and neutron computed tomography.

Two analytical methods based on the neutrons high penetrability, i.e. neutron diffraction (ND) and neutron computed tomography (NCT) were used to investigate the structure of the aragonitic skeleton of an exemplar/sample of Dipastraea pallida (Dana 1846), a modern hermatypic coral. ND was used to reconstruct the orientation distribution function (ODF) of the crystalline fibrils which compose the coral skeleton. Accordingly, 684 ND spectra were analyzed using the Rietveld method. The result confirmed the aragonite as the sole mineral component of coral skeleton, allowing to recalculate the ODF of aragonite fibrils and to represent it by means of (100), (010) and (001) crystallographic planes pole figures (PF). Experimental PF showed a remarkable similarity with PF recalculated by considering that all aragonite fibrils are oriented either along the growth axis of polyp cups or perpendicular to this direction. This result confirmed the previous observations based on optical microscopy, proving at the same time the availability of ND for such types of investigations. In turn, NCT evidenced the individual polyp cups, their interlocked 3D rigid porous structure as well as a periodic variation of density which could be attributed to a seasonal influence of the marine environment. Different from the classical X-ray computed tomography, the NCT, in view of neutron high cross-section for hydrogen, demonstrated the presence of a small amount of organic matter, otherwise transparent for X- and gamma rays.

The Reconstruction of a Bronze Battle Axe and Comparison of Inflicted Damage Injuries Using Neutron Tomography, Manufacturing Modeling, and X-ray Microtomography Data.

A massive bronze battle axe from the Abashevo archaeological culture was studied using neutron tomography and manufacturing modeling from production molds. Detailed structural data were acquired to simulate and model possible injuries and wounds caused by this battle axe. We report the results of neutron tomography experiments on the bronze battle axe, as well as manufactured plastic and virtual models of the traumas obtained at different strike angles from this axe. The reconstructed 3D models of the battle axe, plastic imprint model, and real wound and trauma traces on the bones of the ancient peoples of the Abashevo archaeological culture were obtained. Skulls with traces of injuries originate from archaeological excavations of the Pepkino burial mound of the Abashevo culture in the Volga region. The reconstruction and identification of the injuries and type of weapon on the restored skulls were performed. The complementary use of 3D visualization methods allowed us to make some assumptions on the cause of death of the people of the Abashevo culture and possible intra-tribal conflict in this cultural society. The obtained structural and anthropological data can be used to develop new concepts and methods for the archaeology of conflict.

Spin-induced multiferroicity in the binary perovskite manganite Mn2O3.

The ABO3 perovskite oxides exhibit a wide range of interesting physical phenomena remaining in the focus of extensive scientific investigations and various industrial applications. In order to form a perovskite structure, the cations occupying the A and B positions in the lattice, as a rule, should be different. Nevertheless, the unique binary perovskite manganite Mn2O3 containing the same element in both A and B positions can be synthesized under high-pressure high-temperature conditions. Here, we show that this material exhibits magnetically driven ferroelectricity and a pronounced magnetoelectric effect at low temperatures. Neutron powder diffraction revealed two intricate antiferromagnetic structures below 100 K, driven by a strong interplay between spin, charge, and orbital degrees of freedom. The peculiar multiferroicity in the Mn2O3 perovskite is ascribed to a combined effect involving several mechanisms. Our work demonstrates the potential of binary perovskite oxides for creating materials with highly promising electric and magnetic properties.

Structural and Magnetic Transitions in CaCo3V4O12 Perovskite at Extreme Conditions.

We investigated the structural, vibrational, magnetic, and electronic properties of the recently synthesized CaCo3V4O12 double perovskite with the high-spin (HS) Co2+ ions in a square-planar oxygen coordination at extreme conditions of high pressures and low temperatures. The single-crystal X-ray diffraction and Raman spectroscopy studies up to 60 GPa showed a conservation of its cubic crystal structure but indicated a crossover near 30 GPa. Above 30 GPa, we observed both an abnormally high "compressibility" of the Co-O bonds in the square-planar oxygen coordination and a huge anisotropic displacement of HS-Co2+ ions in the direction perpendicular to the oxygen planes. Although this effect is reminiscent of a continuous HS → LS transformation of the Co2+ ions, it did not result in the anticipated shrinkage of the cell volume because of a certain "stiffing" of the bonds of the Ca and V cations. We verified that the oxidation states of all the cations did not change across this crossover, and hence, no charge-transfer effects were involved. Consequently, we proposed that CaCo3V4O12 could undergo a phase transition at which the large HS-Co2+ ions were pushed out of the oxygen planes because of lattice compression. The antiferromagnetic transition in CaCo3V4O12 at 100 K was investigated by neutron powder diffraction at ambient pressure. We established that the magnetic moments of the Co2+ ions were aligned along one of the cubic axes, and the magnetic structure had a 2-fold periodicity along this axis, compared to the crystallographic one.

Charge-ordering transition in iron oxide Fe4O5 involving competing dimer and trimer formation.

Phase transitions that occur in materials, driven, for instance, by changes in temperature or pressure, can dramatically change the materials' properties. Discovering new types of transitions and understanding their mechanisms is important not only from a fundamental perspective, but also for practical applications. Here we investigate a recently discovered Fe4O5 that adopts an orthorhombic CaFe3O5-type crystal structure that features linear chains of Fe ions. On cooling below ∼150 K, Fe4O5 undergoes an unusual charge-ordering transition that involves competing dimeric and trimeric ordering within the chains of Fe ions. This transition is concurrent with a significant increase in electrical resistivity. Magnetic-susceptibility measurements and neutron diffraction establish the formation of a collinear antiferromagnetic order above room temperature and a spin canting at 85 K that gives rise to spontaneous magnetization. We discuss possible mechanisms of this transition and compare it with the trimeronic charge ordering observed in magnetite below the Verwey transition temperature.

The Pressure-Induced Polymorphic Transformations in Fluconazole.

The structural properties and Raman spectra of fluconazole have been studied by means of X-ray diffraction and Raman spectroscopy at pressures up to 2.5 and 5.5 GPa, respectively. At a pressure of 0.8 GPa, a polymorphic phase transition from the initial form I to a new triclinic form VIII has been observed. At higher pressure of P = 3.2 GPa, possible transformation into another new polymorphic form IX has been detected. The unit cell parameters and volumes, and vibration modes as functions of pressure have been obtained for the different forms of fluconazole.

The polymorphic phase transformations in the chlorpropamide under pressure.

The crystal structure and vibrational spectra of the chlorpropamide have been studied by means of the X-ray diffraction and Raman spectroscopy at pressures up to 24.6 and 4.4 GPa, respectively. Two polymorphic phase transitions, between initial orthorhombic form-A and a monoclinic form-AI at P ∼ 1.2 GPa and, in additional, to another monoclinic form-AII at P ∼ 3.0 GPa, were observed. At pressures above 9.6 GPa, a transformation to the amorphous phase of chlorpropamide was revealed. The lattice parameters, unit cell volumes, and vibration modes as functions of pressure were obtained for the different polymorphic modifications of chlorpropamide.