Role of solute in stress development of nanocrystalline films during heating: An in situ synchrotron X-ray diffraction study

The effect of the solute (Mo) on the stress development of nanocrystalline Ni and Ni–Mo films upon heating has been investigated in real time using in situ synchrotron X-ray diffraction. The complex and distinct relationship between the film stress and grain boundaries (GBs) has been examined by the evolution of real-time intrinsic stress in combination with the in situ grain growth and thermal characterizations. The different intrinsic stress evolutions in the Ni and Ni–Mo films during the heating process result from the modification of GBs by Mo alloying, including GB amorphization, GB relaxation, and GB segregation. It has been found that GBs play a vital role in the stress development of nanocrystalline films. The addition of a solute can not only inhibit grain growth but also influence the stress evolution in the film by changing the atomic diffusivity at the GBs. This work provides valuable and unique insights into the effect of solutes on stress development in nanocrystalline films during annealing, permitting control of the film stress through solute addition and heat treatment, which is critical for improving the design, processing, and lifetime of advanced nanocrystalline film devices at high temperatures

Water is a radiation protection agent for ionised pyrrole

Radiation-induced damage of biological matter is an ubiquitous problem in nature. The influence of the hydration environment is widely discussed, but its exact role remains elusive. Utilising well defined solvated-molecule aggregates, we experimentally observed a hydrogen-bonded water molecule acting as a radiation protection agent for ionised pyrrole, a prototypical aromatic biomolecule. Pure samples of pyrrole and pyrrole(H$_2$O) were outer-valence ionised and the subsequent damage and relaxation processes were studied. Bare pyrrole ions fragmented through the breaking of C$-$C or N$-$C covalent bonds. However, for pyrrole(H$_2$O)$^+$, we observed a strong protection of the pyrrole ring through the dissociative release of neutral water or by transferring an electron or proton across the hydrogen bond. Overall, a single water molecule strongly reduces the fragmentation probability and thus the persistent radiation damage of singly-ionised pyrrole

First-Order Phase Transition of the Schwinger Model with a Quantum Computer

We explore the first-order phase transition in the lattice Schwinger model in the presence of a topological $\theta$-term by means of the variational quantum eigensolver (VQE). Using two different fermion discretizations, Wilson and staggered fermions, we develop parametric ansatz circuits suitable for both discretizations, and compare their performance by simulating classically an ideal VQE optimization in the absence of noise. The states obtained by the classical simulation are then prepared on the IBM's superconducting quantum hardware. Applying state-of-the art error-mitigation methods, we show that the electric field density and particle number, observables which reveal the phase structure of the model, can be reliably obtained from the quantum hardware. To investigate the minimum system sizes required for a continuum extrapolation, we study the continuum limit using matrix product states, and compare our results to continuum mass perturbation theory. We demonstrate that taking the additive mass renormalization into account is vital for enhancing the precision that can be obtained with smaller system sizes. Furthermore, for the observables we investigate we observe universality, and both fermion discretizations produce the same continuum limit

Optical Absorption Properties in Pentacene/Tetracene Solid Solutions

Modifying the optical and electronic properties of crystalline organic thin films is of great interest for improving the performance of modern organic semiconductor devices. Therein, the statistical mixing of molecules to form a solid solution provides an opportunity to fine-tune optical and electronic properties. Unfortunately, the diversity of intermolecular interactions renders mixed organic crystals highly complex, and a holistic picture is still lacking. Here, we report a study of the optical absorption properties in solid solutions of pentacene and tetracene, two prototypical organic semiconductors. In the mixtures, the optical properties can be continuously modified by statistical mixing at the molecular level. Comparison with time-dependent density functional theory calculations on occupationally disordered clusters unravels the electronic origin of the low energy optical transitions. The disorder partially relaxes the selection rules, leading to additional optical transitions that manifest as optical broadening. Furthermore, the contribution of diabatic charge-transfer states is modified in the mixtures, reducing the observed splitting in the 0–0 vibronic transition. Additional comparisons with other blended systems generalize our results and indicate that changes in the polarizability of the molecular environment in organic thin-film blends induce shifts in the absorption spectrum

Protosiphonorhinus patrickmuelleri gen. et sp. nov., the first fossil member of the sucking millipede family Siphonorhinidae (Colobognatha, Siphonophorida) described from Cretaceous Myanmar amber

Millipedes (Diplopoda) are an abundant group of fossilized terrestrial arthropods throughout the Palaeozoic Era. However, there is a gap in the Mesozoic Period with only slightly more than a dozen fossils known, until more recent fossil records – mainly from Cenozoic Dominican and Baltic ambers – became available. Here, we describe a millipede of the family Siphonorhinidae from Myanmar amber, a species-poor group, comprising just six extant genera, disjunctly distributed in Southeast Asia, South Africa, Madagascar, Chile and California. Micro-computed tomography (µ-CT) enabled detailed visualizations of essential elements for description, including the tergites, legs, head, antenna, and notably the gonopods. The new genus shares some characteristics with species of the extant genus Siphonorhinus Pocock, 1894. Protosiphonorhinus patrickmuelleri gen. et sp. nov. differs from extant species of the family mainly in the shape of the antenna, tergites, and anterior gonopods. A recently described fossil species of Siphonophorida from Myanmar amber was erroneously assigned to the family Siphonorhinidae. We transfer it to the family Siphonophoridae, as Siphonophora globosa (Su, Cai & Huang, 2024) comb. nov. The description of the new genus and the reinterpretation of the previously described fossil Siphonorhinidae allows for a rejection of a hypothesis of bradytely within the Siphonorhinidae from the mid-Cretaceous to the present day

Evaluation of the Reinforcing Effect of Intermetallic and Ceramic Phases in a WE54-15%(Vol.%)SiCw Composite Using In Situ Synchrotron Radiation Diffraction

The reinforcing effect of β-Mg$_{14}$YNd$_2$ precipitates and SiC whiskers has been evaluated in a WE54-15%(vol.%)SiC$_w$ composite using synchrotron radiation diffraction during compression tests from room temperature to 300 °C. The addition of SiC whiskers slightly increases the yield stress compared to an unreinforced WE54 alloy. However, whiskers are not effective in increasing the temperature at which the mechanical strength of the unreinforced WE54 alloy begins to decay. The plastic deformation process is controlled by the magnesium matrix over the entire compression temperature range. On one hand, β-Mg$_{14}$YNd$_2$ precipitates assume an additional transferred load from the magnesium matrix just after the yield point in both the WE54 alloy and WE54-15%SiCw composite. The magnitude of transferred load becomes smaller as the temperature increases due to the relaxation process around precipitates. On the other hand, the reinforcing effect of SiC whiskers is greater than that of β-Mg14YNd2 precipitates, although its effect also tends to disappear at temperatures equal to or higher than 200 °C

Top-quark spin correlations as a tool to distinguish pseudoscalar A→ZHA \to ZH and scalar H→ZAH \to ZA signatures in ZttˉZ t \bar t final states at the LHC

Both ATLAS and CMS have recently performed the first searches for a heavy new spin-0 resonance decaying into a lighter new spin-0 resonance and a $Z$ boson, where the lighter spin-0 resonance subsequently decays into $t \bar t$ pairs. These searches are of particular interest to probe Two Higgs doublet model (2HDM) parameter space regions that predict a strong first-order electroweak phase transition. In the absence of CP violation, the investigated decay is possible if the lighter and the heavier spin-0 particles have opposite CP parities. The analysis techniques employed by ATLAS and CMS do not distinguish between the two possible signatures $A \to ZH$ and $H \to ZA$, where $A$ and $H$ denote CP-odd and CP-even Higgs bosons, respectively, if both signals are predicted to have the same total cross sections. We demonstrate the capability of angular variables that are sensitive to spin correlations of the top quarks to differentiate between $A \to ZH$ and $H \to ZA$ decays, even in scenarios where both signals possess identical total cross sections. Focusing on masses of 600 GeV and 800 GeV as a representative 2HDM benchmark, we find that a distinction between the two possible channels is possible with high significance with the anticipated data from the high-luminosity LHC, if the invariant mass distribution of the $t \bar t$ system is further binned in angular variables defined by the direction of flight of the leptons produced in the top-quark decays. Moreover, we find a moderate gain in experimental sensitivity due to the improved background rejection for both signals

Accurate prediction of structural and mechanical properties on amorphous materials enabled through machine-learning potentials: A case study of silicon nitride

Ab initio calculations represent the technique of election to study material system, however, they presentsevere limitations in terms of the size of the system that can be simulated. Often, the results in the simulationof amorphous materials depend dramatically on the size of the system. Here, we overcome this limitation forthe specific case of mechanical properties of amorphous silicon nitride (a-Si3N4) by training a machine learning(ML) interatomic model. Our strategy is based on the generation of targeted training sets, which also includedeliberately stressed structures. Using this dataset, we trained a moment tensor potential (MTP) for a-Si3N4.We show that molecular dynamics simulations using the ML model on much larger systems yield elasticallyisotropic response and can reproduce experimental measurement. To do so, models containing at least ≈3, 500atoms are necessary. The Young’s modulus calculated from the MTP at room temperature is 220 GPa, which isvery well in agreement with the nanoindentation measurement. Our study demonstrates the broader impact ofmachine learning potentials for predicting structural and mechanical properties, even for complex amorphousstructures