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At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

First-principles derivation of magnetic interactions in the triangular quantum spin liquid candidates KYb C h 2 ( C h = S , Se , Te ) and A YbSe 2 ( A = Na , Rb )

The AYb Ch 2 (A=alkali metal, Ch=chalcogen) delafossites are a family of crystals which have a triangular lattice of effective S=1/2 moments on their Yb atoms. They hold great promise for the realization of the triangular quantum spin liquid state because of their defect-minimized growth and the ability to interchange chemical constituencies among the family. Here we use ab initio computations to evaluate the exchange couplings of four realized (and one theoretical) rhombohedral delafossite structures and examine the influence of chemical substitution on promoting the development of a quantum spin liquid state. We find good agreement with experiment regarding the antiferromagnetic nearest-neighbor exchange J 1 , but our calculations underestimate J 2 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Phase Contrast Imaging Diagnostic on DIII-D (1994-2007); Phase Contrast Imaging Diagnostic on DIII-D and Alcator C-Mod (2007-2010); Experimental Study of Waves, Turbulence and Transport, and Model Validation with Phase Contrast Imaging on DIII-D and Alcator C-Mod (2010-2012); Phase Contrast Imaging Diagnostic Upgrade on DIII-D for Measuring High-k Turbulence and Alfven modes (2021-2016); Phase Contrast Imaging Diagnostic Upgrade on DIII-D for Full Multi-Scale Measurements (2016-2020) (Final Report)

This report describes the first twenty-five years of development and use of the Phase Contrast Imaging (PCI) diagnostic for measuring plasma fluctuations on the DIII–D tokamak. One of the key challenges in moving tokamak technology forward to the stage of a nuclear reactor remains understanding how energy and particles are transported across the magnetic field by the action of turbulence and waves, and PCI provides a highly flexible and capable measurement of these fluctuations. The PCI diagnostic uses a laser beam to probe the plasma and optical filtering to produce an amplitude variation on a linear detector array which provides an image of the density waves in the plasma. The PCI covers an exceptional range in frequency and wavelength of the measured fluctuations, allowing observation of plasma-sized magnetohydrodynamic (MHD) modes and ion- and electron-scale turbulence. Modulation of the beam amplitude allows measurement of radio frequency (RF) waves.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Materials Data on C by Materials Project

C crystallizes in the orthorhombic Immm space group. The structure is two-dimensional and consists of two C sheets oriented in the (0, 0, 1) direction. there are nine inequivalent C sites. In the first C site, C is bonded in a trigonal planar geometry to three C atoms. There are a spread of C–C bond distances ranging from 1.39–1.47 Å. In the second C site, C is bonded to four C atoms to form edge-sharing CC4 tetrahedra. There is two shorter (1.52 Å) and two longer (1.60 Å) C–C bond length. In the third C site, C is bonded in a trigonal planar geometry to three C atoms. There are a spread of C–C bond distances ranging from 1.40–1.45 Å. In the fourth C site, C is bonded in a trigonal planar geometry to three C atoms. There is one shorter (1.39 Å) and one longer (1.53 Å) C–C bond length. In the fifth C site, C is bonded in a trigonal planar geometry to three C atoms. Both C–C bond lengths are 1.44 Å. In the sixth C site, C is bonded in a trigonal planar geometry to three C atoms. The C–C bond length is 1.48 Å. In the seventh C site, C is bonded in a trigonal planar geometry to three C atoms. The C–C bond length is 1.39 Å. In the eighth C site, C is bonded in a trigonal planar geometry to three C atoms. In the ninth C site, C is bonded to four C atoms to form edge-sharing CC4 tetrahedra. There is one shorter (1.61 Å) and one longer (1.62 Å) C–C bond length.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on C by Materials Project

C crystallizes in the trigonal R-3m space group. The structure is two-dimensional and consists of three C sheets oriented in the (0, 0, 1) direction. there are six inequivalent C sites. In the first C site, C is bonded in a trigonal planar geometry to three C atoms. There are a spread of C–C bond distances ranging from 1.41–1.45 Å. In the second C site, C is bonded in a trigonal planar geometry to three C atoms. There is one shorter (1.36 Å) and two longer (1.52 Å) C–C bond length. In the third C site, C is bonded to four C atoms to form a mixture of corner and edge-sharing CC4 tetrahedra. There is one shorter (1.51 Å) and two longer (1.60 Å) C–C bond length. In the fourth C site, C is bonded in a trigonal planar geometry to three C atoms. There is one shorter (1.39 Å) and one longer (1.48 Å) C–C bond length. In the fifth C site, C is bonded in a trigonal planar geometry to three C atoms. The C–C bond length is 1.42 Å. In the sixth C site, C is bonded in a trigonal planar geometry to three C atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Measurements of $$ {K}_S^0 $$-$$ {K}_L^0 $$ asymmetries in the decays $$ {\Lambda}_c^{+}\to p{K}_{L,S}^0 $$, $$ p{K}_{L,S}^0{\pi}^{+}{\pi}^{-} $$ and $$ p{K}_{L,S}^0{\pi}^0 $$

Abstract Usinge + e − annihilation data sets corresponding to an integrated luminosity of 4.5 fb −1 , collected with the BESIII detector at center-of-mass energies between 4.600 and 4.699 GeV, we report the first measurements of the absolute branching fractions$$ \mathcal{B}\left({\Lambda}_c^{+}\to p{K}_L^0\right) $$ B Λ c + → p K L 0 = (1.67±0.06±0.04)%,$$ \mathcal{B}\left({\Lambda}_c^{+}\to p{K}_L^0{\pi}^{+}{\pi}^{-}\right) $$ B Λ c + → p K L 0 π + π − = (1.69±0.10±0.05)%, and$$ \mathcal{B}\left({\Lambda}_c^{+}\to p{K}_L^0{\pi}^0\right) $$ B Λ c + → p K L 0 π 0 = (2.02±0.13±0.05)%, where the first uncertainties are statistical and the second systematic. Combining with the known branching fractions of$$ {\Lambda}_c^{+}\to p{K}_S^0 $$ Λ c + → p K S 0 ,$$ {\Lambda}_c^{+}\to p{K}_S^0{\pi}^{+}{\pi}^{-} $$ Λ c + → p K S 0 π + π − , and$$ {\Lambda}_c^{+}\to p{K}_S^0{\pi}^0 $$ Λ c + → p K S 0 π 0 , we present the first measurements of the$$ {K}_S^0 $$ K S 0 -$$ {K}_L^0 $$ K L 0 asymmetries$$ R\left({\Lambda}_c^{+},{K}_{S,L}^0X\right)=\frac{\mathcal{B}\left({\Lambda}_c^{+}\to {K}_S^0X\right)-\mathcal{B}\left({\Lambda}_c^{+}\to {K}_L^0X\right)}{\mathcal{B}\left({\Lambda}_c^{+}\to {K}_S^0X\right)+\mathcal{B}\left({\Lambda}_c^{+}\to {K}_L^0X\right)} $$ R Λ c + K S , L 0 X = B Λ c + → K S 0 X − B Λ c + → K L 0 X B Λ c + → K S 0 X + B Λ c + → K L 0 X in charmed baryon decays:$$ R\left({\Lambda}_c^{+},p{K}_{S,L}^0\right)=-0.025\pm 0.031 $$ R Λ c + p K S , L 0 = − 0.025 ± 0.031 ,$$ R\left({\Lambda}_c^{+},p{K}_{S,L}^0{\pi}^{+}{\pi}^{-}\right)=-0.027\pm 0.048 $$ R Λ c + p K S , L 0 π + π − = − 0.027 ± 0.048 and$$ R\left({\Lambda}_c^{+},p{K}_{S,L}^0{\pi}^0\right)=-0.015\pm 0.046 $$ R Λ c + p K S , L 0 π 0 = − 0.015 ± 0.046 . No significant asymmetries with statistical significance are observed.

Physics↗
DOE OSTI2020

Materials Data on C by Materials Project

C is diamond-like structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are five inequivalent C sites. In the first C site, C is bonded to four C atoms to form corner-sharing CC4 tetrahedra. There is three shorter (1.55 Å) and one longer (1.57 Å) C–C bond length. In the second C site, C is bonded to four C atoms to form corner-sharing CC4 tetrahedra. All C–C bond lengths are 1.55 Å. In the third C site, C is bonded to four C atoms to form corner-sharing CC4 tetrahedra. There is one shorter (1.54 Å) and three longer (1.55 Å) C–C bond length. In the fourth C site, C is bonded to four C atoms to form corner-sharing CC4 tetrahedra. In the fifth C site, C is bonded to four C atoms to form corner-sharing CC4 tetrahedra. The C–C bond length is 1.55 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Ring Size Effects on the Structures of Sandwich Compounds with a Stoichiometry of C 12 H 12 M (M = Ti–Ni)

Ring size effects on geometries and electronic structures were investigated for the (C n H n )M(C m H m ) (n = 4, 5, or 6; m = 8, 7, or 6; m + n = 12; M = Ti–Ni) systems using density functional theory. The lowest-energy C 12 H 12 M structures for the early transition metals titanium, vanadium, and chromium are the experimentally known singlet (η 5 -C 5 H 5 )Ti(η 7 -C 7 H 7 ), doublet (η 5 -C 5 H 5 )V(η 7 -C 7 H 7 ), and singlet (η 6 -C 6 H 6 ) 2 Cr, respectively. The likewise experimentally known singlet (η 6 -C 6 H 6 ) 2 Ti, doublet (η 6 -C 6 H 6 ) 2 V, and singlet (η 5 -C 5 H 5 )Cr(η 7 -C 7 H 7 ) are the secondlowest- energy structures with only a small energy difference between the two vanadium structures. For the later transition metals, dibenzenemetal complexes are the lowest-energy C 12 H 12 M species with two fully bonded hexahapto benzene rings in the lowest-energy manganese and iron derivatives and one hexahapto and one dihapto benzene ring in the lowest-energy cobalt and nickel derivatives. The lowest-energy (C 5 H 5 )M(C 7 H 7 ) structures for the later transition metals iron, cobalt, and nickel have partially bonded nonplanar C 7 H 7 rings with one or two uncomplexed C=C bonds. The (C 4 H 4 )M(C 8 H 8 ) (M = Ti–Ni) structures with the metal sandwiched between four- and eight-membered rings were found to be much higher in energy than their (C 5 H 5 )M(C 7 H 7 ) and (C 6 H 6 ) 2 M isomers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗