Wave-like modulations with non-lattice periodicities accompany a variety of important physical phenomena (e.g. magnetism and superconductivity) and dramatically complicate any quantitative crystal-structure analysis. An exhaustive group-theoretical enumeration of the order parameters that can arise from 1D incommensurate modulations now make it much easier to characterize crystals that behave this way. Figure: Short-range modulation in La1.8Sr2.2Mn2O7.
In this image of from BYU's x-ray diffraction facility, x-rays arriving from the left scatter in all directions from a tiny crystal at the center, and are then imaged by a 16-megapixel x-ray camera. The often beautiful scattering patterns that result contain a wealth of information about the atomic structure of the sample. The speed and sensitivity of state-of-the-art instruments like this have revolutionized the study of crystalline materials.
This is a photo taken in the early evening of September 27, 2015 showing the full moon rising over Y Mountain. This is the last of four total lunar eclipses that were visible during the two year period that began with an Easter eclipse in 2014. This cycle of four total lunar eclipses is known as a tetrad. It is relatively rare to have a cycle such as this coincide with religious holidays such as Easter and so these eclipses were frequently associated with "end of the world" speculation. Photo credit: Dr. Michael D. Joner
Nanoparticles of gamma-alumina obtained from a novel synthetic solvent-deficient method show promise as improved industrial catalyst-supports. X-ray PDF analysis reveals that they are born with a high concentration of defects that locally resemble boehmite. As the nanoparticles are annealed to successively higher temperatures, the boehmite-like defects heal gradually rather than disappearing in an abrupt phase transition, which explains several previously misunderstood of properties of the gamma phase.
The figure shows two different integration "grids," a standard rectangular grid versus an contour-by-contour grid. The Materials Simulation Group (msg.byu.edu) is exploring competing schemes for speeding up the integration of electron bands in materials. An important part of "first-principles" materials calculations involves integrating over the occupied electron states, the so-called "band energy integration." This is the primary source of error in first-principles calculations of solids. Improving this integration would have a dramatic impact on computational simulations of metallic systems.
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Darin Ragozzine et al. recently published an article titled "Physical Characterization of TNOs with the James Webb Space Telescope" in Publications of The Astronomical Society of The Pacific. Click on the image above to read it.
Eagle Aurora over Norway : What's that in the sky? An aurora. A large coronal mass ejection occurred on our Sun five days before this 2012 image was taken, throwing a cloud of fast moving electrons, protons, and ions toward the Earth....
This photograph and Description come from NASA's Astronomy Picture of the Day web site.