Diffuse Scattering from Lamellar Structures

Lamellar structures are formed in a variety of soft materials including lipids, surfactants, block polymers, clays, colloids, semicrystalline polymers and others. Lamellar phases are characterized by scattering patterns containing pseudo-Bragg...

Diffuse scattering model for human brain wave (Alpha) propagation prediction during meditation inside a temple, through ray tracing, a hypothetical study

Electromagnetic radio waves have been propagating for billions of years through the universe since the beginning of time. Electromagnetic radio wave propagation and the communication revolution it spawned, however are products of the twentieth century. Radio propagation in a particular environment is a complex, multipath phenomenon which involves several different mechanisms. According to a traditional, simplified approach, two major urban propagation mechanisms are identified over-roof-top (ORT) or vertical propagation (VP), where one major radial path undergoes multiple diffractions on building tops, and lateral propagation (LP) where several rays reflect/diffract all vertical building walls/edges according to the geometrical Optics (GO) rules before reaching the receiver.

rmc-discord: reverse Monte Carlo refinement of diffuse scattering and correlated disorder from single crystals

A user-friendly program has been developed to analyze diffuse scattering from single crystals with the reverse Monte Carlo method. The approach allows for refinement of correlated disorder from atomistic supercells with magnetic or structural (occupational and/or displacive) disorder. The program is written in Python and optimized for performance and efficiency. Refinements of two user cases obtained with legacy neutron-scattering data demonstrate the effectiveness of the approach and the developed program. It is shown with bixbyite, a naturally occurring magnetic mineral, that the calculated three-dimensional spin-pair correlations are resolved with finer real-space resolution compared with the pair distribution function calculated directly from the reciprocal-space pattern. With the triangular lattice Ba3Co2O6(CO3)0.7, refinements of occupational and displacive disorder are combined to extract the one-dimensional intra-chain correlations of carbonate molecules that move toward neighboring vacant sites to accommodate strain induced by electrostatic interactions. The program is packaged with a graphical user interface and extensible to serve the needs of single-crystal diffractometer instruments that collect diffuse-scattering data.

Diffuse scattering and physical optics in the propagation of electromagnetic waves applied to mobile communications

In this work, the optical theory of physics helps to understand, analyze, and calculate the received power in a fifth-generation mobile telecommunications receiver. In these communication systems there are statistical models and deterministic physical models. We investigated how diffuse scattering in reflection contributes to specular reflection in received power at a receiver due to materials in the propagating environment in a communication channel using millimeter waves. The dimensions of building construction materials have sizes comparable to wavelength at millimeter wave frequencies. The power transmitted by communication equipment can be reflected in the roughness of these apparently smooth materials or spread out in multiple directions. The results show that the contribution due to diffuse scattering must be considered and that deterministic physical models using optical theory are valid and improve predictive analysis with good fit. With these results, the physical theory allows to make software with high precision and that improves the current applications.

A Study of Defects in InAs/GaSb Type-II Superlattices Using High-Resolution Reciprocal Space Mapping

In this paper, he study of defects in InAs/GaSb type-II superlattices using high-resolution an x-ray diffraction method as well as scanning (SEM) and transmission (TEM) electron microscopy is presented. The investigated superlattices had 200 (#SL200), 300 (#SL300), and 400 (#SL400) periods and were grown using molecular beam epitaxy. The growth conditions differed only in growth temperature, which was 370 °C for #SL400 and #SL200, and 390 °C for #SL300. A wings-like diffuse scattering was observed in reciprocal space maps of symmetrical (004) GaSb reflection. The micrometer-sized defect conglomerates comprised of stacking faults, and linear dislocations were revealed by the analysis of diffuse scattering intensity in combination with SEM and TEM imaging. The following defect-related parameters were obtained: (1) integrated diffuse scattering intensity of 0.1480 for #SL400, 0.1208 for #SL300, and 0.0882 for #SL200; (2) defect size: (2.5–3) μm × (2.5–3) μm –#SL400 and #SL200, (3.2–3.4) μm × (3.7–3.9) μm –#SL300; (3) defect diameter: ~1.84 μm –#SL400, ~2.45 μm –#SL300 and ~2.01 μm –#SL200; (4) defect density: 1.42 × 106 cm−2 –#SL400, 1.01 × 106 cm−2 –#SL300, 0.51 × 106 cm−2 –#SL200; (5) diameter of stacking faults: 0.14 μm and 0.13 μm for #SL400 and #SL200, 0.30 μm for #SL300.

Revealing momentum-dependent electron–phonon and phonon–phonon coupling in complex materials with ultrafast electron diffuse scattering

Despite their fundamental role in determining many important properties of materials, detailed momentum-dependent information on the strength of electron–phonon and phonon–phonon coupling across the entire Brillouin zone has remained elusive. Ultrafast electron diffuse scattering (UEDS) is a recently developed technique that is making a significant contribution to these questions. Here, we describe both the UEDS methodology and the information content of ultrafast, photoinduced changes in phonon-diffuse scattering from single-crystal materials. We present results obtained from Ni, WSe2, and TiSe2, materials that are characterized by a complex interplay between electronic (charge, spin) and lattice degrees of freedom. We demonstrate the power of this technique by unraveling carrier–phonon and phonon–phonon interactions in both momentum and time and following nonequilibrium phonon dynamics in detail on ultrafast time scales. By combining ab initio calculations with ultrafast diffuse electron scattering, insights into electronic and magnetic dynamics that impact UEDS indirectly can also be obtained. Graphic Abstract

Int3D: A Data Reduction Software for Single Crystal Neutron Diffraction

We describe a new software package for the data reduction of single crystal neutron diffraction using large 2D detectors. The software consists of a graphical user interface from which the user can visualize, interact with and process the data. The data reduction is achieved by sequentially executing a series of programs designed for performing the following tasks: peak detection, indexing, refinement of the orientation matrix and motor offsets, and integration. The graphical tools of the software allow visualization of and interaction with the data in two and three dimensions, both in direct and reciprocal spaces. They make it easy to validate the different steps of the data reduction and will be of great help in the treatment of complex problems involving incommensurate structures, twins or diffuse scattering.