Stress/Pressure-Stabilized Cubic Polymorph of Li3Sb with Improved Thermoelectric Performance

Li3Sb has two polymorphs crystallizing in a face-centered cubic cell (c-Li3Sb; BiF3 structure type; space group Fm¯3m) and in a hexagonal unit cell (h-Li3Sb; Na3As structure type; space group P63/mmc)....

Reconfigurable topological waveguide based on honeycomb lattice of dielectric cuboids

We show that the photonic crystal (PhC) made of dielectric cuboids with their centers forming a honeycomb lattice is characterized by a ${\mathbb{ℤ}}_{2}$ topological index when the longer sides of six cuboids point towards the center of hexagonal unit cell. While the C6v symmetry regarding the center of unit cell is preserved, the C3 symmetry regarding honeycomb sites is broken, which opens a bandgap in the Dirac dispersion of honeycomb structure and induces a band inversion between p modes and d modes. Rotating cuboids around their individual centers closes the bandgap and reopens a trivial bandgap. We discuss that this feature can be exploited for realizing a reconfigurable topological waveguide.

Röentgenite-(CE) and other ree fluorcarbonates from vein no. 35, Vishnevye mountains, Southern Urals

A mineral assemblage including REE fuorcarbonates (röntgenite-(Ce) Ca2Ce3(CO3)5F3, parisite-(Ce) CaCe2(CO3)3F2, synchisite-(Ce) CaCe(CO3)2F and bastnäsite-(Ce) Ce(CO3)F) was discovered at the dumps of the Vein № 35 open pit, Mt. Dolgaya, Vishnevye Mountains, Southern Urals. These intimately intergrown minerals compose aggregates up to 1 mm in allanite-(Ce)/ferriallanite-(Ce) and chamosite and are associated with microcline, molybdenite, monazite-(Ce), pyrite, thorite, fuorite and fuorannite. The fnd of röntgenite-(Ce) is frst in Urals. Its empirical formula is: (Ca1.98Th0.03)Σ2.01 (Ce1.45La1.02Nd0.32Pr0.11Sm0.03Y0.02Gd0.02)Σ2.97(CO3)5[F2.48(OH)0.52)Σ3.00. The hexagonal unit cell dimensions of the mineral calculated from X-ray powder data are: a = 7.049(1) Å, c = 69.283(30) Å, V = 2981(1) ų. The strongest bands in the Raman spectrum of the mineral are 164, 250, 349, 606, 731, 867, 1091, 1451 and 1737 cm–1.

Rhombohedral trap for studying molecular oligomerization in membranes: application to daptomycin

Diffraction of daptomycin/Ca/Br-DOPG complex trapped in the hexagonal unit cell of rhombohedral phase.

The rise and fall of Weber indices

Weber indices were introduced to provide a unique expression of a lattice direction with respect to the four-axis setting used for hexagonal and rhombohedral crystals. They are in general fractional indices, even in the case of a primitive hexagonal unit cell, but they are often carelessly reduced to integer values. This corresponds, on the one hand, to taking as direction indices the nodes of a lattice further from the origin and, on the other hand, to adopting a hybrid indexing between direct and reciprocal space. A critical analysis of the drawbacks of Weber indices is presented, which justifies the reluctance of crystallographers to adopt them, despite a more widespread use in fields like electron microscopy and metal science.