Polar metals, characterized by the nontrivial coexistence of metallicity and polar structural order, define an emerging frontier in quantum materials research. However, the interplay between their structural phase transitions and fluctuation dynamics remains poorly understood. Here, we reveal distinct diffusive dynamics in metallic lithium rhenium trioxide (LiReO3) associated with its polar-to-nonpolar transition. Unlike isostructural lithium niobate (LiOsO3) and related systems, LiReO3 exhibits pronounced phase fluctuations both above and below Ts. Thermoelectric, Raman, and ultrasound measurements demonstrate a probe-dependent thermal hysteresis, while ultrasound data further show lattice softening and persistent resonant absorption at low temperatures across a broad timescale (1 to 100 microseconds). These observations indicate a multiscale spatiotemporal dynamics governed by a shallow anharmonic potential stabilized by itinerant electrons, as supported by finite-temperature first-principles calculations. By mapping the fluctuation landscape shaped by itinerant electrons, this work offers a previously unexplored perspective for exploiting fluctuation-driven phenomena in polar metals.

It is shown that the presence of hundreds of ppm of water in 1,3-dimethylurea (DMU) powder led to the large depression of the transition temperature between the two enantiotropically related polymorphic forms of DMU (Form II → Form I) from 58 °C to 25 °C, thus explaining the reported discrepancies on this temperature of transition. Importantly, this case study shows that thermodynamics (through the construction of the DMU–water temperature-composition phase diagram) rather than kinetics is responsible for this significant temperature drop. Furthermore, this work also highlights the existence of a monohydrate of DMU that has never been reported before with a non-congruent fusion at 8 °C. Interestingly, its crystal structure, determined from X-ray powder diffraction data at sub-ambient temperature, consists of a DMU–water hydrogen bonded network totally excluding homo-molecular hydrogen bonds (whereas present in forms I and II of DMU).

The persistence of amorphous atorvastatin calcium has been studied as a function of the amorphization method, polymer content, and relative humidity during storage. For amorphization, ball milling, freeze drying, and spray drying have been used. Polyvinylpyrrolidone K40 (PVP) was mixed with atorvastatin in a wide range of concentrations and the resulting amorphous dispersions were subjected to storage conditions with different levels of relative humidity. The analysis of the glass transition temperature of the various samples demonstrates that interactions between atorvastatin calcium and PVP are unfavorable, leading to a destabilization of amorphous atorvastatin, which becomes therefore more prone to recrystallisation. However, mixtures made with spray drying in methanol show an increased glass transition temperature and an increased stability against recrystallisation. PVP may act as a humidity reservoir providing water molecules to amorphous atorvastatin calcium and thus promoting crystallization of the hydrate form. For atorvastatin calcium, the most persistent amorphous sample appears to be that without PVP. It possesses a glass transition temperature as high as 143 degrees C and it remains amorphous for at least a year independent of the humidity level it is subjected to.

Oxychalcogenides are promising candidates for the design of IRnonlinear optical materials. Here, we prepared thefirst oxysulfide in the polarFresnoite mineral type, Ba2SnSSi2O7, and show that it has rare tin square pyramids,SnO4S, with apical Sn-S bond. These units and the Si2O7groups are corner-sharedto form the SnSSi2O7layer with their Sn-S and apical Si-O bonds pointed alongthe polarcaxis. Second harmonic generation measurements reveal that Ba2SnSSi2O7is an IR nonlinear optical (NLO) compound. Formally, Ba2SnSSi2O7results from themineral Fresnoite, Ba2TiOSi2O7, by replacing the TiO5square pyramid with theSnO4S square pyramid. This substitution increases the apical/the equatorial bondratio of the square pyramid, namely, Ti-Oap/Ti-Oeq= 1.66/2.00 = 0.83 in TiO5,and Sn-S/Sn-O = 2.03/2.31 = 0.88 in SnO4S. This change has a major impact onthe cleavage along the stacking polarcaxis and on the second harmonic generationresponse, which decreases from Ba2TiOSi2O7to Ba2SnSSi2O7by a factor greater than2. The atom response theory analyses based on the density functional theory calculations reveal a remarkable difference betweenBa2TiOSi2O7and Ba2SnSSi2O7; the second harmonic generation is positive for the Ti4+ion of Ba2TiOSi2O7but negative for the Sn4+ion of Ba2SnSSi2O7. A Tauc plot analysis for Ba2SnSSi2O7assuming indirect and direct transitions led to the optical band gaps of 2.4and 2.7 eV, respectively.

We report a crystal structure of Boc-L-methionyl glycine methyl ester (MGP) with eight molecules in the asymmetric unit (Z' = 8), which is the highest number in dipeptide compounds. Interestingly, its order-disorder phase transition to the crystal structure of Z' = 4 was observed at -113 degrees C. The reversible order-disorder character of the phase transition was revealed by single-crystal X-ray diffraction and temperature-dependent second harmonic generation (SHG) signal measurements. The disorder of the methionine moiety of the high-temperature phase reflected the conformation of the low-temperature phase, implying that these crystal structures were essentially identical and that atomic displacement due to thermal fluctuation triggered the phase transition. Although differential scanning calorimetry (DSC) analysis and heat capacity (C-p) measurements did not provide clear signals to reveal and detect the character of phase transition, the SHG technique was able to detect the order-disorder structural change. The theoretical calculation clarified the intermolecular interaction energy together with the conformational freedom of the molecule involved in the high-Z' crystal structure of MGP. The comparison study of the lattice energy with the virtually generated low-Z' crystal structures derived from the observed molecular conformations provided quantitative analysis for the general problem in the field of crystallization, namely, why does a molecule crystallize in a high-Z' crystal structure? This study also revealed the contribution of the entropy term, which plays a critical role in understanding the origin of an unusual high-Z' crystal structure.

Nucleation of DL- and L-histidine is examined using induction time measurements and their nucleation rates have been deduced. Results indicate a much slower nucleation for the racemic form compared to...

This article describes the organic-template free synthesis, structural elucidation, thermal stability and conductivity property investigation of the silicon-substituted AlPO-CJ19.

To decide whether an active pharmaceutical ingredient can be used in its amorphous form in drug formulations, often the glass transition is studied in relation to the melting point of the pharmaceutical. If the glass transition temperature is high enough and found relatively close to the melting point, the pharmaceutical is considered to be a good glass former. However, it is obviously important that the observed melting point and glass transition involve exactly the same system, otherwise the two temperatures cannot be compared. Although this may seem trivial, in the case of hydrates, where water may leave the system on heating, the composition of the system may not be evident. Atorvastatin calcium is a case in point, where confusing terminology, absence of a proper an-hydrate form, and loss of water on heating lead to several doubtful conclusions in the literature. However, considering that no anhydrate crystal has ever been observed and that the glass transition of the anhydrous system is found at 144 degrees C, it can be concluded that if the system is kept isolated from water, the chances that atorvastatin calcium crystallises at room temperature is negligible. The paper discusses the various thermal effects of atorvastatin calcium on heating and proposes a tentative binary phase diagram with water.

Crystal structure and kinetic stability of a conglomerateversusthe racemic compound ofp-synephrine.

Mixed-anion compounds are among the most promising systems to design functional materials with enhanced properties. In particular, heteroleptic environments around transition metals allow tuning of the polarity or band-gap engineering for instance. We present the original oxysulfide Ba-5(VO2S2)(2)(S-2)(2), the fifth member in the quaternary system Ba-V-S-O. It exhibits the mixed-anion building units V5+O2S2 and isolated disulfide pairs (S-2)(2-). The structure is solved by combining single-crystal and powder X-ray diffraction and transmission electron microscopy. First-principles calculations were combined in order to highlight the anion roles. In particular, our density functional theory study shows that the 3p states of the disulfide pairs dictate the band gap. In this study, we point out anionic tools for band-gap engineering that can be useful for the design of phases for numerous applications. Finally, third harmonic generation (THG) was measured and compared to the large THG observed for Cu2O, which reveals the potential for nonlinear-optical properties that should be further investigated.

Determination of kryptoracemic compound frequency in the Cambridge Structural Database using CCDC Python API script.

We report a new entry of chiral anti-hyperlipoproteinemia drug showing an excellent preferential enrichment (PE) phenomenon which is not caused by a polymorphic transition during crystallization, but is proposed to occur by a novel mechanism involving partially irregular stacking of R and S homochiral two-dimensional (2D) sheets with a large dipole moment, followed by selective redissolution of one homochiral 2D sheet into the mother liquor during crystallization. The cocrystal composed of ( RS )-2-{4-[(4-chlorophenoxy)methyl]phenoxy}propionic acid (CPPPA) and achiral isonicotinamide exhibited a substantial enrichment in the mother liquor up to 93% ee by simply repeating recrystallization under nonequilibrium conditions using high supersaturation. Furthermore, the deposited crystals with low ee values obtained at the end of PE experiment were second harmonic generation (SHG)-positive, indicating the formation of homochiral domains in the deposited crystals, which reflects the proposed mechanism of PE.

A new entry of chiral anti-hyperlipoproteinemia drug is reported, showing an excellent preferential enrichment (PE) phenomenon which is not caused by a polymorphic transition during crystallization, but is proposed to occur by a novel mechanism involving partially irregular stacking of R and S homochiral two-dimensional (2D) sheets with a large dipole moment, followed by selective redissolution of one homochiral 2D sheet into the mother liquor during crystallization. The cocrystal composed of (RS)-2-{4-[(4-chlorophenoxy)methyl]phenoxy}propionic acid (CPPPA) and achiral isonicotinamide exhibited a substantial enrichment in the mother liquor up to 93 % ee by simply repeating recrystallization under nonequilibrium conditions using high supersaturation. Furthermore, the deposited crystals with low ee values obtained at the end of PE experiment were second harmonic generation (SHG)-positive, indicating the formation of homochiral domains in the deposited crystals, which reflects the proposed mechanism of PE.

A unique superparamagnetic-like behavior and a large "positive magneto-LC effect" were observed in the solid phases and the hexagonal columnar (Col(h)) liquid crystalline (LC) phase, respectively, of novel achiral non-pi-delocalized nitroxide diradical compounds (R,S)-1, which showed polymorphism in the solid phases (solids I and II). The SQUID magnetization measurement revealed that (1) (R,S)-1 containing a small amount of racemic diastereomers (R*,R*)-1 possessed an unusual and large temperature-independent magnetic susceptibility (chi(TIM)>0) component in the original nanocrystalline solid I that was responsible for the observed superparamagnetic-like behavior under low magnetic fields and did not arise from the contamination by extrinsic magnetic metal or metal ion impurities, besides ordinary temperature-dependent paramagnetic susceptibility (chi(para)>0) and temperature-independent diamagnetic susceptibility (chi(dia)<0) components, (2) a large increase in molar magnetic susceptibility (chi(M)) (positive magneto-LC effect) that occurred at the solid I-to-liquid crystal transition upon heating was preserved as an additional chi(TIM) increase in the resulting polymorphic nanocrystalline solid II by cooling, and (3) such unique magnetic phenomena were induced by thermal processing for (R,S)-1 or by adding a small amount of (R*,R*)-1 to (R,S)-1 as the impurity.

Phase transitions of 1-fluoro-adamantane have been thoroughly investigated by ternperature-resolved second harmonic generation (TR-SHG) and X-ray powder diffraction (XRPD). A new polymorph-an intermediate centrosymmetric phase (MT)-between the known orientationally disor-dered high temperature phase (HT, Fm (3) over barm, Z = 4) and the low temperature phase (LT, P (4) over bar2(i)c, Z = 2), was unveiled by TR-SHG. The crystal structure of MT was resolved by XRPD in the P4(2)/nmc (Z = 2) space group, and it is related to the LT phase in a group-subgroup relation. No evidence of any solid-solid transition between these two phases by differential scanning, calorimetry (DSC) or cold-stage microscopy could be obtained. Therefore, combing TR-SHG, XRPD; DSC, and cold-stage microscopy results, a second-order transition mechanism is proposed for the MT <-> LT transition. Moreover, the critical exponent (beta) of the order parameter was Calculated by fitting TR-SHG data to a critical power law. The obtained beta value (0.26) is doge to the value from XRPD data (0.25).