The leucite group structures are tetrahedrally coordinated silicate framework structures with some of the silicate framework cations partially replaced by divalent or trivalent cations. These structures have general formulae A2BSi5O12 and ACSi2O6, where A is a monovalent alkali metal cation, B is a divalent cation, and C is a trivalent cation. These leucites can have crystal structures in several different space groups, dependent on stoichiometry, synthesis conditions, and temperature. Phase transitions are known for temperature changes. This paper reports a high-temperature X-ray powder diffraction study on RbGaSi2O6, which shows a phase transition from I41/a tetragonal to Ia-3d bar on top of 3 cubic on heating from room temperature to 733 K. On cooling to room temperature, the crystal structure reverts to I41/a tetragonal.

The crystal structures of two arylcyclohexylamine derivatives – methoxmetamine·HCl (2-(3-methoxyphenyl)-2-(methylamino)cyclohexan-1-one hydrochloride, MMXE·HCl) and methoxetamine·HCl (2-(ethylamino)-2-(3-methoxyphenyl)cyclohexan-1-one hydrochloride, MXE·HCl) – have been determined using laboratory X-ray powder diffraction data contained in the Powder Diffraction File™. MMXE·HCl and MXE·HCl exhibit anesthetic and sedative effects and have been illicitly used as recreational drugs due to their dissociative hallucinogenic and euphoriant effects. The structure determination of MMXE·HCl and MXE·HCl was carried out with DASH, and the Rietveld refinements were performed with TOPAS Academic in monoclinic unit cells. The parameters obtained for MMXE·HCl were a = 15.0429(5) Å, b = 14.0721(5) Å, c = 6.5716(2) Å, β = 90.9864(14)°, and V = 1,390.91(8) Å3, with Z = 4 and space group P21/n. The parameters obtained for MXE·HCl were a = 8.7772(5) Å, b = 9.9528(7) Å, c = 8.5841(6) Å, β = 100.276(3)°, and V = 737.86(8) Å3, with Z = 2 and space group P21. The structures were validated by dispersion-corrected DFT calculations. Hirshfeld surface analysis and fingerprint plots calculations are also reported.

CrFeCoNi high-entropy alloy (HEA) powder with an equimolar composition was produced via gas atomization and applied as a coating using the cold-spray technique. X-ray diffraction patterns were analyzed to characterize the microstructure of the raw HEA powder and cold-sprayed coatings using Rietveld refinement methods. The HEA powders exhibited a single-phase face-centered cubic crystal structure with a lattice parameter of 0.357349(1) nm, a low microstrain of 4.3(0.17) × 10−4, and a crystallite size of 225(8) nm, attributed to the rapid cooling during atomization. In contrast, the cold-sprayed coatings exhibited broadened diffraction peaks, with a reduced crystallite size of 67.9(1.2) nm and an increased microstrain of 2.2(0.23) × 10−3, showing crystallite size refinement and an increase in the density of crystalline defects due to severe plastic deformation during deposition. Additional microstructural analysis revealed texture in the {200} plane and intrinsic stacking fault probabilities increasing to 4.4(0.21) × 10−3. These findings highlight microstructural changes produced by the cold-spray process. This study provides valuable insights into optimizing cold-spray parameters and tailoring HEA properties for industrial applications.

The crystal structure of resmetirom heminonahydrate Form CSI has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Form CSI had been described previously as a dihydrate. Resmetirom heminonahydrate Form CSI crystallizes in space group P-1 (#2) with a = 11.3094(23), b = 15.158(6), c = 16.570(7) Å, α = 67.405(13), β = 74.425(7), γ = 69.526(7)°, V = 2,427.2(4) Å3, and Z = 4 at 298 K. The crystal structure consists of layers of resmetirom molecules parallel to the bc-plane. These layers are separated by water-rich layers also parallel to the bc-plane. A strong N–H···O links the two resmetirom molecules. The equivalent amino group in the other molecule acts as a donor to a water molecule. A number of C–H···O and C–H···N hydrogen bonds also contribute to the lattice energy. Water molecules act as donors to both O and N in the resmetirom molecules. The structure is more complicated than a hydrogen-bonded framework of resmetirom molecules with water in the pores. The powder pattern has been submitted to the International Centre for Diffraction Data (ICDD) for inclusion in the Powder Diffraction File™ (PDF®).

The crystal structure of fluvoxamine hydrogen maleate has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Fluvoxamine maleate crystallizes in space group P21/c (#14) with a = 21.6310(15), b = 5.3180(4), c = 19.5555(15) Å, β = 99.979(5)°, V = 2,215.48(25) Å3, and Z = 4 at 298 K. The crystal structure consists of alternating double layers of cations and anions parallel to the bc-plane. Hydrogen bonds link the layers of anions and cations parallel to the bc-plane. The powder pattern has been submitted to the International Centre for Diffraction Data for inclusion in the Powder Diffraction File™ (PDF®).

The crystal structure of Form A of dequalinium chloride has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Dequalinium chloride Form A crystallizes in space group P42212 (#94) with a = 26.2671(8), c = 9.1119(4) Å, V = 6,286.9(4) Å3, and Z = 8 at 298 K. Despite the conventional representation of the cation, the ring N atoms are not positively charged. The positive charges are distributed on the ring carbon atoms ortho and para to these N atoms. The central decyl chain conformation is more kinked than the all-trans that might be expected in the solid state, but contains only one unusual torsion angle. The crystal structure consists of an array of dequalinium cations, with chloride anions located in regions between the cations. There are short stacks of roughly parallel rings in multiple directions. There is only one classical hydrogen bond in the structure, N–H···Cl between one of the amino groups and one of the chloride anions. Several C–H···Cl hydrogen bonds are prominent, involving ring, chain, and methyl hydrogen atoms as donors. Particularly noteworthy are the hydrogen bonds from the first and second C atoms at each end of the decyl chain. The powder pattern has been submitted to the International Centre for Diffraction Data (ICDD) for inclusion in the Powder Diffraction File™ (PDF®).

The crystal structure of protriptyline hydrochloride has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Protriptyline hydrochloride crystallizes in space group P21/n (#14) with a = 10.10772(19), b = 32.0908(6), c = 10.45302(21) Å, β = 92.8748(10)°, V = 3,386.33(15) Å3, and Z = 8 at 298 K. The crystal structure contains the expected N–H···Cl hydrogen bonds, which link the cations and anions into crankshaft-shaped chains along the c-axis. The cations and the anions form layers parallel to the ac-plane, with van der Waals interactions between the layers. The powder pattern has been submitted to the International Centre for Diffraction Data (ICDD®) for inclusion in the Powder Diffraction File™ (PDF®).

The crystal structure of racemic afoxolaner has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Afoxolaner crystallizes in space group P21/a (#14) with a = 9.6014(6), b = 14.0100(11), c = 39.477(10) Å, β = 94.389(7)°, V = 5,294.7(17) Å3, and Z = 8 at 298 K. The crystal structure consists of layers of molecules parallel to the ab-plane. The boundaries of the layers are rich in halogens. Within the layers, there is parallel stacking of rings along both the a- and b-axes. Two classical N–H···O hydrogen bonds link the two independent molecules into dimers. The powder pattern has been submitted to the International Centre for Diffraction Data (ICDD®) for inclusion in the Powder Diffraction File™ (PDF®).

Isaac Newton spent some four decades researching “chymistry,” the early modern equivalent of our chemistry. Although his laboratory notebooks survive, his experimental goals remain obscure to the present day. Our work reveals that Newton was engaged in fruitful chemical research even by modern standards. Replication of his experiments, involving Newton’s “vitriol” (from his “liquor of antimony,” NH4Cl, HNO3, and Sb2S3) and verdigris (Cu(CH3COO)2), produced a variety of NH4+-, Cl−-, SO4−2-, NO3−-, and Cu-containing crystallization products. We analyzed these products using powder X-ray diffraction (XRD) (Cu Kα radiation) and Rietveld refinement, which revealed a complex mixture of (NH4)2Cu(SO4)2(H2O)6, NH4NO3, NH4Cl, (NH4)2CuCl4(H2O)2, and (NH4)[Cu(NH3)2Cl3]⋅2H2O. The XRD data also consistently showed a suite of peaks unmatched by any phase in the PDF-5 database. A crystal of the unknown product was analyzed using single-crystal X-ray methods (Mo Kα radiation), revealing a previously unknown compound, (NH4)2[Cu2Cl2(C2H3O2)4]·2NH4Cl, with space group Pmna and room-temperature unit-cell parameters of a = 14.550(3) Å, b = 8.850(1) Å, and c = 9.116(2) Å. The inclusion of this phase in the Rietveld refinements yielded a satisfactory fit. Our ongoing replications of Newton’s crystallization experiments reveal that his research produced a complex, unusual suite of phases, including the aforementioned previously unknown compound.

BaLa2Cu1−xBaxTi2O9 (x = 0.00, 0.15, and 0.30) ceramics were synthesized in polycrystalline form via the conventional solid-state reaction techniques in air. The crystal structure of the title compositions was characterized by room-temperature X-ray powder diffraction and analyzed using the Rietveld refinement method. All the compositions crystallize in the tetragonal symmetry of space group I4/mcm (No. 140) with cell volumes: 249.43(1) Å3 for x = 0.00, 249.42(1) Å3 for x = 0.15, and 250.05(1) Å3 for x = 0.30. The tilt system of the MO6 octahedra (M = Cu(Ba2)/Ti) corresponds to the notation a0a0c−. The MO6 octahedra share the corners via oxygen atoms in 3D. Along the c-axis, the octahedra are connected by O(1) atoms of (0, 0, 1/4) positions; while in the ab-plane, they are linked by O(2) atoms of (x, x + 1/2, 0) positions. The bond angle of M–O2–M is 168.6(7)° for x = 0.00, 168.6(6)° for x = 0.15, and 166.8(6)° for x = 0.30, whereas the bond angle of M–O1–M is constrained to be 180° by space group I4/mcm.

Linear Temporal Logic (LTL) offers a formal way of specifying complex objectives for Cyber-Physical Systems (CPS). In the presence of uncertain dynamics, the planning for an LTL objective can be solved by model-free reinforcement learning (RL). Surrogate rewards for LTL objectives are commonly utilized in model-free RL for LTL objectives. In a widely adopted surrogate reward approach, two discount factors are used to ensure that the expected return (i.e., the cumulative reward) approximates the satisfaction probability of the LTL objective. The expected return then can be estimated by methods using the Bellman updates such as RL. However, the uniqueness of the solution to the Bellman equation with two discount factors has not been explicitly discussed. We demonstrate, through an example, that when one of the discount factors is set to one, as allowed in many previous works, the Bellman equation may have multiple solutions, leading to an inaccurate evaluation of the expected return. To address this issue, we propose a condition that ensures the Bellman equation has the expected return as its unique solution. Specifically, we require that the solutions for states within rejecting bottom strongly connected components (BSCCs) be zero. We prove that this condition guarantees the uniqueness of the solution, first for recurrent states (i.e., states within a BSCC) and then for transient states. Finally, we numerically validate our results through case studies.

Neural network (NN)-based control policies have proven their advantages in cyber-physical systems (CPS). When an NN-based policy fails to fulfill a formal specification, engineers leverage NN repair algorithms to fix its behaviors. However, such repair techniques risk breaking the existing correct behaviors, losing not only correctness but also verifiability of initial state subsets. That is, the repair may introduce new risks, previously unaccounted for. In response, we formalize the problem of Repair with Preservation (RwP) and develop Incremental Simulated Annealing Repair (ISAR). ISAR is an NN repair algorithm that aims to preserve correctness and verifiability—while repairing as many failures as possible. Our algorithm leverages simulated annealing on a barriered energy function to safeguard the already-correct initial states while repairing as many additional ones as possible. Moreover, formal verification is utilized to guarantee the repair results. ISAR is compared to a reviewed set of state-of-the-art algorithms, including (1) reinforcement learning-based techniques (STLGym and F-MDP), (2) supervised learning-based techniques (MIQP and minimally deviating repair) and (3) online shielding techniques (tube MPC shielding). Upon evaluation on two standard benchmarks, OpenAI Gym mountain car and an unmanned underwater vehicle, ISAR not only preserves correct behaviors from previously verified initial state regions, but also repairs 81.4% and 23.5% of broken state spaces in the two benchmarks. Moreover, the signal temporal logic (STL) robustness of the ISAR-repaired policies is higher than the baselines.