Comment on "Origin of correlated isolated flat bands in copper-substituted lead phosphate apatite"

In this comment on "Origin of correlated isolated flat bands in copper-substituted lead phosphate apatite" (arXiv:2307.16892 [cond-mat.supr-con]), we discuss the flat half-occupied two-band manifold that appears in $\mathrm{Pb}_9\mathrm{Cu}(\mathrm{PO}_4)_6(\mathrm{OH})_2$ when using a semilocal DFT functional. We argue that the flat band is an artifact of the functional's overestimation of the energy of the oxygen p states in the valence band. When using the HSE hybrid functional, the energy of the oxygen p states is reduced, and the copper-derived manifold splits into one fully occupied and one empty band. While these results do not rule out the possibility of superconductivity in doped LK-99, they do predict that stoichiometric $\mathrm{Pb}_9\mathrm{Cu}(\mathrm{PO}_4)_6(\mathrm{OH})_2$ is an insulator, not a superconductor. Furthermore, we have shown that future first-principles studies of these materials should employ hybrid functionals or other advanced methods to ensure that the oxygen-derived valence-band energies are correctly described.Comment: 2 pages, 1 figur

Lone-Pair Stereochemistry Induces Ferroelectric Distortion and the Rashba Effect in Inorganic Halide Perovskites

The lone-pair s states of germanium, tin, and lead underlie many of the unconventional properties of the inorganic metal halide perovskites. Dynamic stereochemical expression of the lone pairs is well established for perovskites based on all three metals, but previously only the germanium perovskites were thought to express the lone pair crystallographically. In this work, we use advanced first-principles calculations with a hybrid functional and spin-orbit coupling to predict stable monoclinic polar phases of $\mathrm{CsSnI}_3$ and $\mathrm{CsSnBr}_3$, which exhibit a ferroelectric distortion driven by stereochemical expression of the tin lone pair. We also predict similar metastable ferroelectric phases of $\mathrm{CsPbI}_3$ and $\mathrm{CsPbBr}_3$. In addition to ferroelectricity, these phases exhibit the Rashba effect. Spin splitting in both the conduction and valence bands suggests that nanostructures based on these phases could host bright ground-state excitons. Finally, we discuss paths toward experimental realization of these phases via electric fields and tensile strain.Comment: 21 pages, 4 figure

Trends in Public Opinion, 1989-1996

In this chapter, we examine the party identifications and ideological orientations of Tennesseans from 1989 through 1996, as revealed through survey research. We also look at Tennesseans\u27 positions on several issues of public policy that have been salient in state politics during this period. Our intent is to isolate any trends in the partisan and ideological character of the state while examining citizens\u27 positions on key issues

Strength of Headed Shear Studs in Cold-formed Steel Deck

Results from 57 push-out tests of headed shear studs in cold-formed steel deck are presented. The results are compared to predicted strengths using the American Institute of Steel Construction Load and Resistance Factor Design Specification. The results indicate that the AISC specification does not accurately predict the strength of the shear studs placed in steel deck

Guidebook for field trips in central New Hampshire and contiguous areas: 63rd annual meeting October 2 and 3, 1971 Concord, New Hampshire: table of contents, maps, forward

front matte

Guidebook for field trips in central New Hampshire and contiguous areas: 63rd annual meeting October 2 and 3, 1971 Concord, New Hampshire

Geologic fieldtrips in New Hampshir

Source of Lake Vostok Cations Constrained with Strontium Isotopes

Lake Vostok is the largest sub-glacial lake in Antarctica. The primary source of our current knowledge regarding the geochemistry and biology of the lake comes from the analysis of refrozen lake water associated with ice core drilling. Several sources of dissolved ions and particulate matter to the lake have been proposed, including materials from the melted glacier ice, the weathering of underlying geological materials, hydrothermal activity and underlying, ancient evaporitic deposits. A sample of Lake Vostok Type 1 accretion ice has been analyzed for its 87Sr/86Sr signature as well as its major cation and anion and Sr concentrations. The strontium isotope ratio of 0.71655 and the Ca/Sr ratio in the sample strongly indicate that the major source of the Sr is from aluminosilicate minerals from the continental crust. These data imply that at least a portion of the other cations in the Type 1 ice also are derived from continental crustal materials and not hydrothermal activity, the melted glacier ice, or evaporitic sources

Double-Rashba materials for nanocrystals with bright ground-state excitons

While nanoscale semiconductor crystallites provide versatile fluorescent materials for light-emitting devices, such nanocrystals suffer from the "dark exciton"\unicode{x2014}an optically inactive electronic state into which the nanocrystal relaxes before emitting. Recently, a theoretical mechanism was discovered that can potentially defeat the dark exciton. The Rashba effect can invert the order of the lowest-lying levels, creating a bright excitonic ground state. To identify materials that exhibit this behavior, here we perform an extensive high-throughput computational search of two large open-source materials databases. Based on a detailed understanding of the Rashba mechanism, we define proxy criteria and screen over 500,000 solids, generating 173 potential "bright-exciton" materials. We then refine this list with higher-level first-principles calculations to obtain 28 candidates. To confirm the potential of these compounds, we select five and develop detailed effective-mass models to determine the nature of their lowest-energy excitonic state. We find that four of the five solids (BiTeCl, BiTeI, Ga$_2$Te$_3$, and KIO$_3$) can yield bright ground-state excitons. Our approach thus reveals promising materials for future experimental investigation of bright-exciton nanocrystals.Comment: 19 pages, 4 figure

The Advanced Glycation End Product, N\u3csup\u3eE\u3c/sup\u3e-(Carboxymethyl)lysine, Is a Product of Both Lipid Peroxidation and Glycoxidation Reactions

Nepsilon-(Carboxymethyl)lysine (CML) is an advanced glycation end product formed on protein by combined nonenzymatic glycation and oxidation (glycoxidation) reactions. We now report that CML is also formed during metal-catalyzed oxidation of polyunsaturated fatty acids in the presence of protein. During copper-catalyzed oxidation in vitro, the CML content of low density lipoprotein increased in concert with conjugated dienes but was independent of the presence of the Amadori compound, fructoselysine, on the protein. CML was also formed in a time-dependent manner in RNase incubated under aerobic conditions in phosphate buffer containing arachidonate or linoleate; only trace amounts of CML were formed from oleate. After 6 days of incubation the yield of CML in RNase from arachidonate was approximately 0.7 mmol/mol lysine compared with only 0.03 mmol/mol lysine for protein incubated under the same conditions with glucose. Glyoxal, a known precursor of CML, was also formed during incubation of RNase with arachidonate. These results suggest that lipid peroxidation, as well as glycoxidation, may be an important source of CML in tissue proteins in vivo and that CML may be a general marker of oxidative stress and long term damage to protein in aging, atherosclerosis, and diabetes

The isolation of upper management

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30694/1/0000339.pd