The crystal structure determines many of the physical properties of oxide perovskites (ABO3) and only a tiny modification of the lattice structure causes major changes in the functional properties through the interplay among spin, orbital and charge orders. The determination of distortions and their associated symmetries is a valuable asset for understanding the structure properties relationship and guiding the design of epitaxial oxide heterostructures and correlated electronic states. Here, the in-depth structural characterization of a 50 nm-LaVO3 thin film grown onto (110)-oriented DyScO3 by molecular beam epitaxy is reported. The heterostructure is investigated by means of X-ray diffraction, high-resolution and scanning transmission electron microscopies, scanning precession electron diffraction tomography and first-principles calculations. LaVO3 crystallizes in the orthorhombic Pbnm space group and is constrained by the substrate, which imposes a growth along the [110] orthorhombic direction, over the 140 deposited unit cells. The mapping of the reciprocal space allows determining the orientation of the film and refining the lattice parameters. Using scanning transmission electron microscopy, the structure of LaVO3 is analyzed, focusing on the determination of the antipolar displacement of the rare earth. Additionally, 3D electron diffraction enables to resolve the atomic positions of all species within the film.

• Keywords
• atomic positions, distortions, orthorhombic perovskite, strain, thin film,
• Publication type
• Journal Article MeSH

The regulation of topological structures and pattern formation has attracted wide attention in the field of condensed matter. Liquid crystals (LCs), as a class of soft matter, uniquely combine fluidity with anisotropic properties, making them ideal systems for exploring defect dynamics. When confined systems are subjected to external stimuli, LCs can exhibit a variety of topological defects. The recent discovery of ferroelectric nematics (NF), characterized by high permittivity and spontaneous polarization, has opened new possibilities for technological applications, enriching the landscape of accessible topological phenomena. In this study, we demonstrate the formation of tunable two-dimensional arrays of topological defects in an NF compound, induced by an alternating electric field in sandwich cells without pre-patterning. These defects self-organize into pseudo-square lattices, with their character and periodicity governed primarily by the frequency of the applied field and, to a lesser extent, by the cell thickness. We attribute the emergence of these structures to the interplay between elastic and electric forces appearing as a result of polar molecular reorientation. Our findings offer a promising approach for generating reconfigurable, spatially periodic polarization patterns, with potential relevance to future soft-matter-based devices and tunable photonic systems.

• Publication type
• Journal Article MeSH

Structural, chemical, and extrinsic modifications of graphene-based nanostructures enable bandgap tuning, optoelectronics, spintronics, and quantum materials design. A well-known approach to modify their electronic properties involves introducing nonbenzenoid ring topologies in their ideal sp2-hybridized hexagonal lattice, such as azulene or Stone-Wales (SW) defects. However, despite the unique structural and electronic characteristics that these nonalternant defects induce, their systematic incorporation in graphene-based nanostructures remains challenging. Here, we demonstrate the on-surface synthesis of one-dimensional SW-based polymers linked through cumulene bonds on the Au(111) surface via thermal and visible-light-induced reactions of a tailored molecular precursor. Scanning tunneling and noncontact atomic force microscopies reveal the nonplanar structure of SW-based units within the polymer chain, while the chemical structure of the polymer has been verified by Raman spectroscopy in combination with theoretical modeling. Additionally, scanning tunneling spectroscopy measurements show an experimental bandgap of 1.8 eV, which significantly differs from its isostructural cumulene-bridged bisanthene analogs. Our results highlight the critical role of SW defects in the structural and electronic properties of carbon-based conjugated polymers, advancing their design with prospects in next-generation optoelectronic devices.

• Keywords
• Carbon‐based polymers, Non‐contact atomic force microscopy, Scanning tunneling microscopy, Stone‐Wales defect, Surface chemistry,
• Publication type
• Journal Article MeSH

This study investigates venetoclax solvates and their nonsolvated forms through desolvation. Seven solvates were prepared and their structures solved from single-crystal X-ray diffraction data. Among these, two are cavity solvates while the remaining five are channel solvates, with three being isomorphous. Desolvation experiments led to two solvent-free crystalline polymorphs of venetoclax, forms A and B. Notably, the acetone solvate remained stable and did not convert to a nonsolvated form. Form B has a higher melting point and a faster intrinsic dissolution rate than form A. Advanced computational tools, including Solvate Analyser and CSD-Particle, provided insights into crystal surface properties and desolvation behaviour. Properties such as lattice energy, molecular interaction energy, attachment energy, surface rugosity and solvent arrangement within the crystal and on the surface were linked to solvate stability and subsequent transformation upon desolvation. A combination of FTIR, and 13C and 15N solid-state NMR spectroscopies showed that both short- and long-range molecular interactions and arrangements of venetoclax molecules in the desolvated forms closely resembled those in the parent solvates.

• Keywords
• Cambridge Structural Database, crystal engineering, crystal morphology, crystal structures, desolvation, intermolecular interactions, pharmaceuticals, polymorphism, solvates, venetoclax,
• Publication type
• Journal Article MeSH

The use of ultrashort laser pulses to manipulate properties or investigate a materials response on femtosecond time-scales enables detailed tracking of charge, spin, and lattice degrees of freedom. When pushing the limits of experimental resolution, connection to theoretical modeling becomes increasingly important to infer causality relations. Weyl-semimetals are a particular class of materials of recent focus due to the topological protection of the Weyl-nodes, resulting in a number of fundamentally interesting phenomena. This work provides a first-principles framework based on time-dependent density-functional theory for tracking the distribution of Weyl-nodes in the Brillouin-zone following an excitation by a laser pulse. Investigating the prototype material TaAs, we show that residual shifts in the Weyl-Nodes' position and energy distribution are induced by a photo-excitation within femto-seconds through band-structure renormalization. Further, we provide an analysis of the relaxation pathway of the photoexcited band-structure through lattice vibrations.

• Keywords
• Electronic properties and materials, Electronic structure, Ultrafast photonics,
• Publication type
• Journal Article MeSH

This work introduces an extension of an existing thermodynamic model for gas hydrates based on the van der Waals and Platteeuw (vdWP) approach for structure H (sH) hydrates. A model for the hydrate volume is adapted to the hexagonal unit cell with a universal correlation for the thermal expansion, guest-specific lattice parameters at reference conditions, a compressibility relation given in terms of the Murnaghan equation of state (EOS), and a multi-layered description of the hydrate cavities. Available experimental data for the lattice parameters are represented within ±0.05 Å, while molecular simulation predictions show larger deviations. The results allow for the determination of lattice parameters for 10 help gases and 15 large-guest molecule substances (LGMSs), which enables the application to a wide range of hydrate-forming mixtures. In combination with multiparameter EOS for fluid phases, i.e., the IAPWS-95 for water, the proposed vdWP-type model is validated by comparing predicted hydrate formation conditions with experimental data for methylcyclohexane or 2-methylbutane containing mixtures, demonstrating good agreement. The fluid EOS for methylcyclohexane systems with water, carbon dioxide, and methane and 2-methylbutane with water is revised.

• Publication type
• Journal Article MeSH

Supramolecular assembly driven by weak C-H⋯S[double bond, length as m-dash]P/O and CH⋯HC contacts was studied in a new bis(thiophosphoramide) structure, {(C2H5O)2P(S)}2N2C4H8, using X-ray crystallography and DFT computational methods. Combined QTAIM/noncovalent interaction (NCI) and natural bond orbital (NBO) analyses were used to gain deeper insights into the nature, energy and strengths of these contacts. The C-H⋯O hydrogen bond was found to be the strongest interaction, followed by two H⋯H and then H⋯S contacts. Crystal lattice energy calculations were performed, and the components contributing to the intermolecular interactions were investigated and discussed (electrostatic, polarization, dispersion and repulsion). The dispersion forces were found to be the most prominent in the network energy. The relative contributions of the intermolecular contacts were visualized by Hirshfeld surfaces and two-dimensional fingerprint diagrams. Some topics related to geometry and conformation were also studied.

• Publication type
• Journal Article MeSH

A2Ir2O7iridates were proven to crystallise in the geometrically frustrated pyrochlore structure, which remains stable upon rare-earth cation substitution, temperature variation, and external pressure application. However, the change of interatomic distances and local distortions in the lattice frequently leads to complex electronic properties. The low-temperature behaviour in light-A iridates has been thoroughly investigated, including its evolution with pressure. The present pressure study reports the electrical transport and magnetotransport properties in heavy rare-earth Lu2Ir2O7and Er2Ir2O7. Both compounds reveal a semiconductor-insulator transition induced by the antiferromagnetic ordering of the all-in-all-out (AIAO) type in the Ir sublattice. The transition monotonously shifts to a higher temperature under applied pressure by approximately 20 K at 3 GPa. As the transition in resistivity originates in the antiferromagnetic order, the latter is expected to be enhanced with the applied pressure as well. Upon cooling the compound in a magnetic field, the AIAO/AOAI domain structure with non-zero net magnetic moment is formed, mirroring itself in an asymmetric term in the magnetoresistivity of Lu2Ir2O7. The application of pressure then enhances the asymmetric term. The same behaviour is proposed for the whole heavy rare-earth A2Ir2O7series (A= Gd-Lu), although with magnetoresistivity features masked significantly by a stronger response of magneticAcations.

• Keywords
• A2Ir2O7, AFM domains, conductivity, hydrostatic pressure, magnetoresistivity, pyrochlore,
• Publication type
• Journal Article MeSH

High-entropy alloys have emerged as a class of materials, offering unique properties due to their irregular and randomized arrangement of multiple elements in an ordered lattice. This concept has been extended to two-dimensional (2D) van der Waals materials, including transition metal dichalcogenides (TMD), which exhibit promising applications in electrocatalysis. In this work, we have explored the synthesis of entropy mixture crystals (TMDmix) involving the chemical vapor transport of five individual elements, Mo and W as metal elements, S, Se, and Te as chalcogenide elements, resulting in a crystalline structure with a controlled composition Mo0.56W0.44(S0.33Se0.35Te0.32)2, with an estimated ΔSmix of 0.96R. When observed along the [001] zone axis, STEM HAADF images indicate the presence of the different crystal phases of the 2D TMDs (1T, 2H, and 3R). Our findings demonstrate the potential of the entropy TMDmix materials as catalysts for the hydrogen evolution reaction, offering an alternative to noble metal-based catalysts. To maximize the potential of TMDmix, we chose chemical exfoliation with the resulting material being subdivided into size groups, big and small, according to their lateral size. In an acidic medium, the lowest overpotential of 127 mV and a Tafel slope of 79 mV/dec were obtained for the exfoliated sample with a small lateral size (exf-TMDsmall).

• Keywords
• 2D material, Electrocatalysis, High Entropy Alloys, Hydrogen Evolution Reaction, Transition Metal Dichalcogenide,
• Publication type
• Journal Article MeSH

Dual-ion batteries (DIBs) have been extensively explored due to their low material costs, high power density, and eco-friendly characteristics. However, the graphite cathode often leads to structural damage and instability at the electrode/electrolyte interface, severely diminishing its electrochemical performance. This work presents a cost-effective approach from the perspective of electrolyte optimization to overcome these challenges. By incorporating a moderate amount (5 wt %) of vinylene carbonate (VC) as an additive into a mixed solvent of dipropylene glycol methyl ether (DPM) and water, significant improvements in electrochemical performance are achieved, primarily due to the formation of a sulfur-rich cathode electrolyte interface (CEI) on the graphite surface and the electrolyte additive fostering the generation of nanosized sulfide particles in the graphite lattice, which provide active storage sites for anions. In the graphite-Zn DIB, a high discharge-specific capacity of 140 mAh g-1 was achieved at 100 mA g-1, and after 500 cycles, the capacity retention rate is 84.2%, which is much higher than that of the battery without VC. This work demonstrates the potential of a cost-effective electrolyte in optimizing the composition of the graphite cathode CEI and promoting the formation of inorganic nanoparticle hosts on the graphite cathode surface for enhancing the performance of DIBs.

• Keywords
• cathode electrolyte interface, dipropylene glycol methyl ether, dual-ion battery, graphite cathode, zinc metal anode,
• Publication type
• Journal Article MeSH