Virtually unlimited solar cell experiments

EurekAlert  March1, 2021 Researchers in Japan used machine learning to screen hundreds of thousands of donor: acceptor pairs based on an algorithm trained with data from previously published experimental studies. Trying all possible combinations of 382 donor molecules and 526 acceptor molecules resulted in 200,932 pairs that were virtually tested by predicting their energy conversion efficiency. Basing the construction of our machine learning model on an experimental dataset drastically improved the prediction accuracy. To verify this method, one of the polymers predicted to have high efficiency was synthesized in the lab and tested. Its properties were found to conform with […]

Jumping frost crystals: Lab works toward electrostatic de-icing

Phys.org  February 24, 2021 Charge separation in frost has been studied in the past, but the effect has never been exploited to remove the frost from its surface. A team of researchers in the US (Virginia Tech, UC Santa Barbara) exploited the spontaneous electrification of ice to reveal a surprising phenomenon of jumping frost dendrites. They observed frost dendrites breaking off from mother dendrites and/or the substrate to jump out-of-plane toward an opposing polar liquid. They developed analytical and numerical models to estimate the attractive force between the frost dendrites and liquid and found it to be in good agreement […]

Quickly identify high-performance multi-element catalysts

Eurekalert  February 17, 2021 Many electrochemical reactions go through several steps. Each should be optimized on a catalyst surface if possible, but different requirements apply to each step. With the example of the oxygen reduction reaction, an international team of researchers (Denmark, Germany) showed that for high entropy alloys comprising five or more principal elements, by utilizing a data‐driven discovery cycle, the multidimensionality challenge raised by this catalyst class can be mastered. Iteratively refined computational models predict activity trends around which continuous composition‐spread thin‐film libraries are synthesised. High throughput characterisation datasets are then used as input for refinement of the […]

Defects may help scientists understand the exotic physics of topology

Science Daily  January 22, 2021 Researchers at the University of Illinois engineered metamaterials to include defects to show that defects and structural deformations can provide insights into a real material’s hidden topological features. They experimentally demonstrated that disclination defects can robustly trap fractional charges in topological crystalline insulators (TCI) metamaterials, and the trapped charge can indicate non-trivial, higher-order crystalline topology even in the absence of any spectral signatures. They uncovered a connection between the trapped charge and the existence of topological bound states localized at these defects. By testing the robustness of these topological features when the protective crystalline symmetry […]

Experimental evidence of an intermediate state of matter between a crystal and a liquid

EurekAlert  January 19, 2021 Researchers in Russia present a detailed analysis of their experimental study, which shows clear evidence of a two-stage melting process of a quasi-two-dimensional dusty plasma system in a high-frequency gas discharge. They accurately calculated global parameters of the orientational and translational order, as well as their susceptibilities to determine two critical points, related to “solid-to-hexatic” and “hexatic-to-liquid” phase transitions. The nature of the emerging defects and changes in their mutual concentration, in addition to the estimate of core energy of free dislocations also counts in favor of the formation of an intermediate hexatic phase. These results […]

Machine-learning models of matter beyond interatomic potentials

EurekAlert  January 7, 2021 The electronic density of states (DOS) quantifies the distribution of the energy levels that can be occupied by electrons in a quasiparticle picture and is central to modern electronic structure theory and underpins the computation and interpretation of experimentally observable material properties such as optical absorption and electrical conductivity. An international team of researchers (Switzerland, UK) studied the configurations of silicon spanning a broad set of thermodynamic conditions, ranging from bulk structures to clusters and from semiconducting to metallic behavior and compared different approaches to represent the DOS, and the accuracy of predicting quantities such as […]

Old silicon learns new tricks

Science Daily  January 6, 2021 Using a combination of standard dry etching and chemical etching an international team of researchers (Japan, China) fabricated arrays of pyramid-shaped silicon nanostructures. An ultrathin layer of iron was deposited onto the silicon to impart unusual magnetic properties. The pyramids’ atomic-level orientation defined the orientation and thus the properties-of the overlaying iron. Epitaxial growth of iron enabled shape anisotropy of the nanofilm. The curve for the magnetization as a function of the magnetic field was rectangular-like shaped but with breaking points which were caused by asymmetric motion of magnetic vortex bound in pyramid apex. They […]

Stretching diamond for next-generation microelectronics

Science Daily  December 31, 2020 An international team of researchers (Hong Kong, Taiwan, China, USA – UC Berkeley, Lawrence Berkeley National Laboratory, MIT) microfabricated single-crystalline diamond bridge structures with ~1 micrometer length by ~100 nanometer width and achieved sample-wide uniform elastic strains under uniaxial tensile loading at room temperature. They demonstrated deep elastic straining of diamond microbridge arrays. The ultra large, highly controllable elastic strains can fundamentally change the bulk band structures of diamond, including a substantial calculated bandgap reduction as much as ~2 electron volts. Their findings have shown the potential of strained diamonds as prime candidates for advanced […]

Artificial intelligence solves Schrödinger’s equation

Phys.org  December 21, 2020 The goal of quantum chemistry is to predict chemical and physical properties of molecules based solely on the arrangement of their atoms in space, avoiding the need for resource-intensive and time-consuming laboratory experiments. In principle, this can be achieved by solving the Schrödinger equation. Up to now, it has been impossible to find an exact solution for arbitrary molecules that can be efficiently computed. To solve this problem researchers in Germany have proposed PauliNet, a deep-learning wavefunction ansatz that achieves nearly exact solutions of the electronic Schrödinger equation for molecules with up to 30 electrons. PauliNet […]

Ultra-thin designer materials unlock quantum phenomena

Science Daily  December 17, 2020 Exotic states such as topological insulators, superconductors and quantum spin liquids are often challenging or impossible to create in a single material. The problem can be circumvented by deliberately selecting the combination of materials in heterostructures so that the desired physics emerges from interactions between the different components. An international team of researchers (Finland, Poland, Japan) used molecular-beam epitaxy to grow 2D islands of ferromagnetic chromium tribromide on superconducting niobium diselenide. They used low-temperature scanning tunneling microscopy and spectroscopy to reveal the signatures of one-dimensional Majorana edge modes. The fabricated 2D van der Waals heterostructure […]