We report the synthesis methodology, structure, and intrinsic properties of ultra-high quality single crystals of MnTe, an archetypal altermagnet. The crystals, obtained from self-flux method, are nearly free from crystal imperfections and disproportionate chemical compositions as seen by various investigation methods. In measurements under quasi free-standing configuration minimizing stress induced effects, the crystals exhibit complex and anisotropic domain kinetics in both superheating and supercooling regimes around the altermagnetic transition at T_N = 310 K. An Anderson insulating state is observed below T_MI≈ 150 K with a carrier density of about 1.6× 10^17 cm^-3, being sharply contrast to metallic states usually seen in Te-deficit samples. Nevertheless, hallmarks of altermagnetism, anomalous Hall effect and X-ray magnetic circular dichroism signal, are robust in this intrinsic limit, however with significantly reduced magnitudes.

Gd-doped ceria (GDC) is a key functional oxide for applications in catalysis and solid oxide fuel cells, where control over phase purity, dopant incorporation, and defect chemistry at the nanoscale is critical. Here, we use in situ synchrotron powder X-ray diffraction to identify synthesis conditions to obtain GdxCe1-xO2-x/2 nanoparticles in a one-step process. GDC nanoparticles with 0.0 ≤ x ≤ 0.3 are subsequently synthesized by a continuous-flow hydrothermal method using simple cerium and gadolinium nitrates and urea as precursors. Systematic variation of synthesis temperature and pH demonstrates that supercritical conditions (400  °C) under basic pH are required for the formation of a homogeneous fluorite solid solution under hydrothermal conditions. Ex situ synchrotron PXRD with Rietveld refinement reveals a monotonic lattice expansion from 5.41370(2) to 5.42701(7)  Å with increasing Gd content, accompanied by increased microstrain and a reduction of crystallite size from 7 to 4 nm. Pair distribution function analysis and STEM-EDX mapping indicate limited local disorder, with no evidence of defect ordering or clustering. A statistically distributed arrangement of Gd ions and oxygen vacancy defects is favorable for obtaining high oxygen mobility at relatively low temperatures. This contrasts with the correlated defects known in oxygen conductors such as yttria-stabilized hafnia.

Machine learning and artificial intelligence approaches are expected to accelerate the development of new materials, e.g., through automated synthesis. Here, we investigate another approach to accelerate materials discovery, namely in situ synchrotron Powder X-ray diffraction (PXRD), which enables efficient exploration of a large range of synthesis parameters to identify optimal synthesis conditions. We study the solvothermal formation of PdxMy (M = Si, Ge, Sn, Pb) nanoparticles with varying temperature, solvent, and metal precursor. Intermetallic phases are obtained for all systems except for PdxSiy, and specific conditions are identified for preparing Pd25Ge9, Pd2Ge, SnPd2, Sn13Pd20, SnPd, Pb3Pd5, Pb9Pd13, PbPd, and Pb2Pd intermetallic phases. A general formation mechanism is suggested, where Pd nanoparticles are formed initially, followed by absorption and diffusion of the secondary metal to form intermetallic phases. Based on the learnings from the in situ experiments, SnPd2, Sn13Pd20, and SnPd nanoparticles are synthesized ex situ in a simple solvothermal process. Scanning transmission electron microscopy - energydispersive X-ray spectroscopy (STEM-EDS) establishes a gradient of Sn across the nanoparticles with a Pd-rich core and increasing Sn content towards the edges, reflecting the diffusion of Sn into the initial Pd nanoparticles and thereby corroborating the formation mechanism observed from the in situ data.

Hybrid organic-inorganic crystals are attractive due to their large structural diversity and easy fabrication. Polyoxometalates, including polyoxovanadates (POVs), have gained interest e.g. for biomedical or battery applications and they can be prepared with a plethora of cationic matrices to balance the anionic charge of the metal-oxo cluster. Here, we employ a simple solvothermal synthesis to produce hybrid organic-inorganic crystals between the anionic "inorganic" vanadate and the cationic "organic" metal-ethylenediamine (en) complexes [M(en)n]. A series of different 3d metals were tested with Co (reported in a previous publication), Ni, Cu and Zn, producing crystals of high enough quality for single crystal X-ray diffraction structure investigation Co, preferring the +3 oxidation state, forms crystals in the supernatant between [Co(en)3] and 1D (V4O13) POVs with chains of corner-sharing (V5+O4)-tetrahedra. The other 3d metals, Ni, Cu and Zn, prefer the +2 oxidation state and form crystals in the precipitate with mixed oxidation state (V4+/V5+) spherical (V15O36) or (V18O42) molecular POVs. The (V15O36) or (V18O42) POV morphology is selectively tuneable by pH when using the amphoteric Zn precursor. We report the crystal structures of 4[Ni(en)3]·(V18O42Cl)·13.26(H2O), 4[Cu(en)2]·(V18O42Cl)·4(H2O), and a high-quality structure of 2[Zn(en)2(enH)](V15O36Cl)(enH2)·5.63 H2O crystallizing in the orthorhombic space group Pbca.

High-temperature polymorphs of hafnia (HfO 2 ) are of significant interest in electronics and fuel-cell applications, and stabilization at ambient conditions can be achieved by aliovalent substitution and nanosize effects. Y 3+ stabilization of hafnia (YSH) introduces local cation disorder around charge-compensating oxygen-ion vacancies, and here we establish both the average and local structure of YSH nanoparticles using synchrotron powder X-ray diffraction (PXRD) and pair distribution function (PDF) analysis. A range of phase-pure crystalline nanoparticles of Hf 1– x Y x O 2– x /2 were prepared via continuous flow solvothermal synthesis and subsequent high-temperature annealing, and full stabilization of the cubic phase is achieved already at 13 at% Y 3+ . The average structure conforms to the cubic fluorite phase of HfO 2 , but local displacive disorder caused by electrostatic attraction of neighbouring oxygen ions and repulsion of neighbouring metal ions by the net-positive oxygen-ion vacancies is established. The well-known Zr 3 Y 4 O 12 structure, which incorporates such relaxation motifs, provides a good proxy description of YSH. In situ X-ray total scattering experiments provide insight into the formation mechanism of the YSH nanoparticles and initial precipitation of an atomically mixed amorphous phase is followed by crystallization over several minutes. The crystallization rate increases with higher reaction temperature, whereas an increased doping level results in slower crystallization.

Zirconium dioxide (ZrO2) is widely used as a structural ceramic and in various technological applications, where performance often depends on stabilizing the high-temperature t-ZrO2 phase under ambient conditions. However, green synthesis routes using benign precursors typically yield phase mixtures dominated by the thermodynamically stable m-ZrO2 phase. Here, in situ X-ray scattering is used to investigate the solvothermal synthesis of ZrO2 nanoparticles across different solvents (methanol, ethanol, 2-propanol, ethylene glycol, and water) and temperatures (150-400 degrees C). The metastable t-ZrO2 phase forms initially as a kinetic phase in all syntheses except water before the transition into the m-ZrO2 phase in a solid-state transformation. The conditions required to isolate a phase-pure t-ZrO2 product are established, demonstrating the in situ solvothermal synthesis as an efficient screening tool. Ex situ continuous-flow solvothermal synthesis is then employed to reproduce the required conditions, enabling the isolation of phase-pure t-ZrO2. Continuous flow solvothermal synthesis is an efficient green method for production of nanoparticles, and the fast heating rate and flexible design provide versatility to reach the short reaction time required in this case.

A combination of experimental methods and computational techniques have been used to investigate the composition of the zinc ferrite (ZnFe2O4) (111) single crystal surface under different preparation methods. Surface-sensitive XPS and NEXAFS measurements show that upon annealing in ultra-high vacuum (UHV), Zn depletion occurs, leading to the formation of an iron-rich (11 1) surface, whereas annealing in the presence of O2 gas maintains a more bulk-like ZnFe2O4 surface composition. Analysis of the Fe 2p photoemission (XPS) and Fe L edge X-ray absorption signals shows a clear difference in iron oxidation state and distribution between the two different preparation conditions. After annealing in UHV, a mixed Fe2+/Fe3+ oxidation state and a cation distribution like that of a magnetite (Fe3O4) structure is observed, whereas after annealing in oxygen gas only Fe3+, mostly in octahedral coordination, is observed, as expected for a ZnFe2O4 structure. Temperature-dependent XPS confirms significant Zn depletion in the near-surface region above 500 degrees C under UHV, with almost no Zn remaining at 600 degrees C; under an O2 atmosphere no zinc depletion is observed up to 600 degrees C. A theoretical model based on DFT simulations illustrates how reduction from ZnFe2O4 to Fe3O4 with formation of O2 and Zn gas is thermodynamically feasible under UHV conditions, whereas the same reaction is not favourable at higher oxygen partial pressures. Our findings demonstrate the strong impact that UHV treatment has on zinc ferrite surfaces, and cautions that UHV environments, routinely employed for surface analysis, can themselves induce substantial modifications to the surface, thereby complicating the interpretation of measurements in the context of catalytically relevant conditions.

Nickel phosphides are considered excellent candidates as catalysts for the oxygen evolution reaction (OER) under alkaline conditions. This study first investigates the nucleation and growth of Ni2P during hydrothermal synthesis by in situ powder X-ray diffraction. It is found that Ni2P nanoparticles are formed throughout the temperature range of 150 degrees C to 300 degrees C, but above 225 degrees C a transition of Ni2P to Ni12P5 is observed. Data recorded at multiple temperatures allow activation energies for the nucleation of Ni2P, growth of Ni2P, and the Ni2P to Ni12P5 phase transitions to be estimated as 91.0(5) kJ mol-1, 62.3(9) kJ mol-1, and 115.5(7) kJ mol-1, respectively. The in situ data further reveals that the Ni2P crystallite sizes can be controlled by varying the reaction time and temperature, and correspondingly ex situ autoclave syntheses were performed to obtain phase-pure Ni2P nanoparticles with sizes of similar to 20 nm, similar to 25 nm, and similar to 30 nm. Furthermore, with short reaction times partly amorphous similar to 20 nm and similar to 25 nm Ni2P nanoparticles are obtained. Using fully crystalline standards, the crystallinity of the nanoparticles is determined to infer amorphous impurities, and the effects of both crystallinity and crystallite size for the nanoparticle Ni2P catalyst towards OER under alkaline conditions are established. The crystalline Ni2P nanoparticle samples show an almost constant overpotential ranging from 413 to 417 mV and a minor increase in the Tafel slope from 60.5 to 71.7 mV dec-1 with increasing crystallite size. In contrast, the Ni2P nanoparticles with excess amorphous phosphorus exhibit significantly higher Tafel slopes of 95.8 (similar to 20 nm) and 89.6 mV dec-1 (similar to 25 nm). Absolute crystallinity is very rarely quantified in studies of nanoparticle catalysts, but the present results highlight that crystallinity determination can be used to suggest the presence of amorphous impurities, which in this case have a larger impact than crystallite size when optimizing electrode characteristics for electrocatalytic water splitting.

A combination of experimental methods and computational techniques have been used to investigate the composition of the zinc ferrite (ZnFe2O4) (111) single crystal surface under different preparation methods. Surface-sensitive XPS and NEXAFS measurements show that upon annealing in ultra-high vacuum (UHV), Zn depletion occurs, leading to the formation of an iron-rich (111) surface, whereas annealing in the presence of O2 gas maintains a more bulk-like ZnFe2O4 surface composition. Analysis of the Fe 2p photoemission (XPS) and Fe L edge X-ray absorption signals shows a clear difference in iron oxidation state and distribution between the two different preparation conditions. After annealing in UHV, a mixed Fe2+/Fe3+ oxidation state and a cation distribution like that of a magnetite (Fe3O4) structure is observed, whereas after annealing in oxygen gas only Fe3+, mostly in octahedral coordination, is observed, as expected for a ZnFe2O4 structure. Temperature-dependent XPS confirms significant Zn depletion in the near-surface region above 500 °C under UHV, with almost no Zn remaining at 600 °C; under an O2 atmosphere no zinc depletion is observed up to 600 °C. A theoretical model based on DFT simulations illustrates how reduction from ZnFe2O4 to Fe3O4 with formation of O2 and Zn gas is thermodynamically feasible under UHV conditions, whereas the same reaction is not favourable at higher oxygen partial pressures. Our findings demonstrate the strong impact that UHV treatment has on zinc ferrite surfaces, and cautions that UHV environments, routinely employed for surface analysis, can themselves induce substantial modifications to the surface, thereby complicating the interpretation of measurements in the context of catalytically relevant conditions.

Chemical bonding determines the intrinsic properties of materials, but despite the super-strong metallic magnet Nd 2 Fe 14 B being a vital compound in modern life, the local chemical environment is not well understood. Nd 2 Fe 14 B has a very complex crystal structure with six independent Fe sites, two independent Nd sites and one B site, which in concert are responsible for the extremely high magnetic moment. Dense inorganic materials with excellent crystal quality and heavy atoms represent a strong challenge to X-ray charge density analysis, and indeed Nd 2 Fe 14 B has a mere suitability factor of 0.02 compared with 3–5 for typical organic molecular crystals. Here, we report high-energy (λ = 0.2482 Å) 25 K single-crystal synchrotron X-ray diffraction data suitable for multipole modelling of the X-ray charge density. The X-ray electron density shows local anisotropy in the bonding environment of the Fe atoms, and topological analysis quantifies that the Nd atoms are positive (∼+1), one Fe atom and B are negative (−1.7 and −0.44, respectively), and the remaining Fe atoms are close to neutral (±0.1). The d orbitals of all Fe atoms are close to being evenly populated, and bonding analysis establishes a multidirectional `metal-like' framework. It is found that a single Fe atom is crucial for the 3D framework of the magnetic structure. Through structural refinement of synchrotron single-crystal X-ray diffraction data at 25 K, 100 K, 200 K and 300 K, anisotropic displacement parameters are obtained, and the Debye temperature is estimated to be 345–383 K.

A nonmixing solvothermal flow reactor has been designed and commissioned to allow for precise control of residence time during synthesis of crystalline nanoparticles. Benchmarking of the reactor was performed against a conventional T-mixing flow reactor at 200, 250, 300, and 350 degrees C (P = 250 bar) by synthesizing phase-pure anatase TiO2 nanoparticles from an industrial-grade TiOSO4 precursor. Characterization was carried out using PXRD, TEM, UV-vis, and Raman spectroscopy revealing highly anisotropic particles with constant crystallite sizes of similar to 10 nm in the (100) basal plane and decreasing sizes along the [001] direction with increasing temperatures (from similar to 19 to similar to 14 nm). A residence time study using the nonmixing reactor confirmed that the crystallite size in the (100) plane is invariant to temperature (250-350 degrees C), residence time, and reactor design. At 350 degrees C, the crystallite size along [001] was stable at 14 nm, while at 250 degrees C, larger nanoparticles (16-19 nm) formed with increasing residence time. This study highlights the new reactor's capability for controlled synthesis of anisotropic anatase nanoparticles and its easy optimization of synthesis parameters.

Zero thermal expansion is a rare but desirable physical property for materials. Here, we report an unprecedented near-zero thermal expansion (nZTE) behavior in a two-dimensional (2D) coordination polymer (CP) Cd(1,2,4-triazole) 2 (H 2 PO 4 ) 2 (Cd-Tz) across a broad temperature range of 25 K–400 K. Using multi-temperature high-resolution single-crystal X-ray diffraction, we investigated the structural dynamics of the wine-rack-like framework of Cd-Tz and compared it with that of positive thermal expansion (PTE) CPs Zn-Tz and Mn-Tz with similar framework topology. We show that nZTE in Cd-Tz is a consequence of two monotonic and opposing trends with PTE ( α a , α c ∼22 MK −1 ) in the ac plane and negative thermal expansion (NTE) in the b direction ( α b ∼−47 MK −1 ). A new mechanism for the uniaxial NTE is established based on concerted out-of-plane single atom libration of similarly oriented adjacent triazole rings in the wine-rack motifs. X-ray electron density analysis and modeling of low-temperature vibrational anharmonicity reveals the role of Cd-triazole bonds and hydrogen bonds in promoting the single atom libration. Tuning the metal−ligand bonding strength through minor substitution of Zn/Mn (∼8/12%) in the Cd-Tz lattice results in a prominent shift from nZTE to NTE behavior in the solid solution phases.

Chain-like thermoelectric materials generally exhibit anisotropic transport properties, providing a promising platform for decoupling electrical and thermal properties. In this study, we reveal the intrinsic origin of anisotropic electrical transport in chain-like thermoelectric InTe single crystals, and demonstrate that having nearedge electronic bands primarily composed of atomic orbitals oriented perpendicular to the chain direction (p(x,) (y) orbitals in InTe) is beneficial to optimizing thermoelectric properties through anisotropy. This orbital configuration strengthens orbital interactions, reduces the conductivity effective mass, and improves carrier mobility along the interchain ([110]) direction, yielding a remarkable improvement in electrical conductivity and power factor compared to the intrachain ([001]) direction. Furthermore, the weak van der Waals interchain interactions naturally suppress lattice thermal conductivity along [110], enabling the decoupling of electrical and thermal transport properties. Experimentally, we synthesized Al-doped InTe single crystals, confirming that Al doping preserves the intrinsic band anisotropy and enhances electrical transport along the interchain direction. A peak zT of 0.82 at 750 K is achieved along [110] in a In0.99Al0.01Te single crystal, representing a 3.2-fold enhancement over the [001] direction. This work provides fundamental insights into leveraging atomic orbital interactions for anisotropic transport optimization in chain-like thermoelectric materials.

InSe is a van der Waals semiconductor in which mechanical flexibility, high electronic mobility, and non-trivial electronic structures converge, making it an attractive platform for both intriguing fundamental studies and promising device developments. However, the nucleation and growth of phase-pure, intrinsic InSe crystals require stringent thermodynamic conditions, and have therefore remained elusive. Since InSe melts incongruently, the widely used synthesis methods based on cooling of a 1 : 1 In-Se mixture will produce either aggregates of multiphase crystallites or uncontrolled In-rich, heavily electron-doped InSe. This fundamental thermodynamic constraint provides a compelling explanation for the large discrepancies observed in the reported physical properties of InSe. We overcome these limitations by utilizing the travelling solvent floating zone (TSFZ) method to produce high quality, centimeter-size InSe single crystals. Electrical, thermal, and thermoelectric transport measurements demonstrate that TSFZ-InSe single crystals closely approach the intrinsic limit, establishing it as a benchmark material for the future studies of this important material.

Macropore flow in structured soils is an important process determining the transport of water, contaminants, and nutrients in the soil. Therefore, we also expect a close connection between hydraulic conductivity (k(h)) near saturation and the potential of macropore flow. In combination with measurements of soil hydraulic properties (SHPs), tracer breakthrough characteristics can be used to get an insight into the understanding of macropore flow in structured soils. In this study, we aim to investigate if a direct link exists between tracer breakthrough characteristics and SHPs of structured soils, which may partly explain the dynamics and the spatial variation of solute transport in soils. We hypothesize that a direct relationship exists between the characteristics of breakthrough curves (BTCs) and the near-saturated k(h) of the soil. We used SHPs and tracer breakthrough characteristics for 71 undisturbed topsoil columns (20 cm height, 20 cm diameter) sampled from eight different sites in Denmark. We defined k[10] (near-saturated hydraulic conductivity) as k(h) at a matric potential (h) of -10 cm. On the same soil columns, based on the tracer breakthrough experiment, we calculated the 5%, 25%, and 50% arrival times (ATs) as the percentage of the cumulative relative mass of the tritium tracer leaching through the soil column. Linear mixed models (LMMs) effectively captured the linear relationships among variables. However, applying a machine learning method (Gradient Boosting Decision Trees, GBDT) further clarified the importance of predictors by capturing nonlinear threshold effects and key interactions among soil hydraulic properties. Although the overall predictive accuracy of GBDT was slightly lower compared to LMM, both methods consistently highlighted k[10] as the most influential predictor, emphasizing its key role in preferential flow dynamics. We conclude that linking SHPs with tracer breakthrough characteristics on large intact columns is highly useful for characterizing soil macropore functions.

Materials with low thermal conductivity are important for a variety of applications such as thermal barrier coatings and thermoelectrics, and understanding the underlying mechanisms of low heat transport, as well as relating them to structural features, remains a central goal within material science. Here, we report on the ultralow thermal conductivity of the quarternary crystalline silver chalcogenide AgGaGe 3 Se 8 , with a remarkable value of only 0.2 watts per meter per kelvin at room temperature and an unusual glass-like thermal behavior from 2 to 700 kelvin. The ultralow thermal conductivity is linked to a disordered nature of silver in the structure, displaying extremely large silver atomic displacement parameters obtained from multitemperature synchrotron powder x-ray scattering measurements and silver ionic conductivity at elevated temperatures. In addition, a low-temperature Boson peak in the heat capacity and a low Debye temperature of 158 kelvin reveal signs of structural anharmonicity and soft bonding.

Magnetic anisotropy of the central metal atom is a crucial property of single molecule magnets (SMMs). Small structural changes can alter the magnetic properties, and accurate experimental methods to investigate magnetic anisotropy are therefore critical. Here, we investigate two five-coordinated Co(ii) SMMs, [CoCl2Cltpy] (1) and [CoBr2Cltpy] (2) (Cltpy = 4'-chloro-2,2':6',2''-terpyridine), through multiple techniques. Ab initio theoretical calculations performed on the two compounds show that both possess axial magnetic anisotropy with the magnetic easy axis pointing towards one of the terminal halogen atoms. Theoretical calculations on SMMs are typically done on isolated molecular species, and to validate this approximation the magnetic anisotropy was further studied through experimental techniques. EPR measurements confirm an axial anisotropy of 1, and magnetic measurements provide experimental Zero-Field Splitting (ZFS) parameters, showing that the values from theoretical calculations are slightly overestimated. The X-ray electron density determined from 20 K single-crystal synchrotron X-ray diffraction data provides estimated d-orbital populations also suggesting axial magnetic anisotropy in both systems, and furthermore suggesting a more pronounced axiality in 1 compared to 2. This is in good agreement with the results obtained from both magnetic measurements and theoretical calculations. The magnetic anisotropy of 1 is quantified experimentally through polarized powder neutron diffraction via the site susceptibility method, confirming an axial magnetic anisotropy of the compound. A slight deviation in the easy axis direction is observed between experimental and theoretical results. This, together with the overestimation of the ZFS parameters from theoretical calculations, shows that experimental investigation of the magnetic anisotropy of SMMs is of high relevance.

Despite great interest in the properties of the Ag2Ch (Ch = S, Se, Te) compounds, their complex crystal structures, envisioned as a disordered liquid-like Ag substructure, are poorly understood. This limits our understanding of the structural origin of their attractive properties. From combined powder X-ray diffraction (PXRD) and X-ray total scattering (TS) in the temperature range of 300-800 K, the average and local structures for all three Ag2Ch compounds have been probed simultaneously for both the room-temperature (RT) and first high-temperature (HT) polymorphs. From Rietveld refinement of the PXRD data, large and highly anisotropic atomic displacement parameters were identified for Ag in all RT polymorphs, which cannot be attributed solely to thermal displacement. Furthermore, the Rietveld models struggle with describing the highly diffuse distribution of Ag in the HT polymorphs, especially for Ag2S and Ag2Se, for which the maximum entropy method (MEM) is better suited. By comparing pair distribution functions (PDFs), it is found that the local structure cannot be described by the periodic Rietveld model alone at any temperature. New structural descriptions are proposed to account for these observations, in which Ag is displacively disordered in the RT polymorphs, and the lattice is locally distorted in the HT polymorphs to resemble the RT structure due to strong Ag-Ch interactions. Thus, the chalcogenide framework is far from being rigid, the Ag substructure is far from being liquid, and both are governed by specific local chemical interactions.

In situ and operando pair distribution function (PDF) studies are becoming commonly used to study chemical reactions, nucleation and growth of nanoparticles, or structural changes during the operation of batteries, catalysts, thermoelectric devices etc. However, repeated time-resolved total scattering experiments and subsequent PDF analysis are often not prioritized due to the scarce synchrotron beam time available. This means that the experimental uncertainty and reproducibility of the experimental methods are unknown, and the full potential of in situ PDF experiments may not be exploited. Here, we quantify the experimental uncertainty of the PDF technique in an in situ study of the hydro-thermal synthesis of ZrO2 nanoparticles. Systematic variation of the parameters used to obtain the PDF shows that the user-defined parameters can potentially affect the chemical conclusions obtained from the time-resolved experiment. We found that comparable results are best obtained using the same input parameters across different experiments. We also compare different PDF algorithms to examine whether the processing algorithm influences the chemical analysis.