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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on U(Cr3P2)2 by Materials Project

U(Cr3P2)2 crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. U is bonded to six equivalent Cr and six equivalent P atoms to form distorted UCr6P6 cuboctahedra that share edges with six equivalent CrU2P4 tetrahedra and faces with two equivalent UCr6P6 cuboctahedra. All U–Cr bond lengths are 2.95 Å. All U–P bond lengths are 2.83 Å. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded to two equivalent U and four P atoms to form distorted CrU2P4 tetrahedra that share corners with eight equivalent CrU2P4 tetrahedra, edges with two equivalent UCr6P6 cuboctahedra, edges with four equivalent CrU2P4 tetrahedra, and faces with two equivalent CrU2P4 tetrahedra. There are two shorter (2.33 Å) and two longer (2.37 Å) Cr–P bond lengths. In the second Cr site, Cr is bonded in a 5-coordinate geometry to five P atoms. There are four shorter (2.37 Å) and one longer (2.48 Å) Cr–P bond lengths. There are two inequivalent P sites. In the first P site, P is bonded in a 9-coordinate geometry to nine Cr atoms. In the second P site, P is bonded in a 8-coordinate geometry to two equivalent U and six Cr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(Al10Cr)2 by Materials Project

U(CrAl10)2 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. U is bonded in a 4-coordinate geometry to sixteen Al atoms. There are four shorter (3.11 Å) and twelve longer (3.17 Å) U–Al bond lengths. Cr is bonded to twelve Al atoms to form CrAl12 cuboctahedra that share corners with six equivalent CrAl12 cuboctahedra, edges with eighteen equivalent AlUAl10Cr cuboctahedra, and faces with six equivalent AlUAl10Cr cuboctahedra. There are six shorter (2.54 Å) and six longer (2.78 Å) Cr–Al bond lengths. There are three inequivalent Al sites. In the first Al site, Al is bonded in a distorted linear geometry to two equivalent U and twelve equivalent Al atoms. All Al–Al bond lengths are 3.07 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent Cr and ten Al atoms. There are a spread of Al–Al bond distances ranging from 2.70–2.82 Å. In the third Al site, Al is bonded to one U, one Cr, and ten Al atoms to form distorted AlUAl10Cr cuboctahedra that share corners with fifteen equivalent AlUAl10Cr cuboctahedra, edges with two equivalent AlUAl10Cr cuboctahedra, edges with three equivalent CrAl12 cuboctahedra, a faceface with one CrAl12 cuboctahedra, and faces with fifteen equivalent AlUAl10Cr cuboctahedra. There are a spread of Al–Al bond distances ranging from 2.68–2.90 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(GaCu3)2 by Materials Project

U(Cu3Ga)2 crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are two inequivalent U sites. In the first U site, U is bonded in a 9-coordinate geometry to fifteen Cu and four Ga atoms. There are a spread of U–Cu bond distances ranging from 3.01–3.26 Å. There are one shorter (3.42 Å) and three longer (3.44 Å) U–Ga bond lengths. In the second U site, U is bonded in a 9-coordinate geometry to fifteen Cu and three equivalent Ga atoms. There are a spread of U–Cu bond distances ranging from 3.02–3.35 Å. All U–Ga bond lengths are 3.29 Å. There are three inequivalent Cu sites. In the first Cu site, Cu is bonded in a 11-coordinate geometry to two U, six Cu, and three Ga atoms. There are a spread of Cu–Cu bond distances ranging from 2.55–2.66 Å. There are a spread of Cu–Ga bond distances ranging from 2.44–2.77 Å. In the second Cu site, Cu is bonded to three U, six Cu, and three Ga atoms to form a mixture of edge, corner, and face-sharing CuU3Ga3Cu6 cuboctahedra. Both Cu–Cu bond lengths are 2.49 Å. There are two shorter (2.61 Å) and one longer (2.89 Å) Cu–Ga bond lengths. In the third Cu site, Cu is bonded in a 11-coordinate geometry to three U, six Cu, and two equivalent Ga atoms. Both Cu–Ga bond lengths are 2.50 Å. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded in a 11-coordinate geometry to two U, eight Cu, and one Ga atom. The Ga–Ga bond length is 2.95 Å. In the second Ga site, Ga is bonded in a 10-coordinate geometry to one U, nine Cu, and three equivalent Ga atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(SiOs)2 by Materials Project

U(OsSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. U4+ is bonded in a 8-coordinate geometry to eight equivalent Os2- atoms. All U–Os bond lengths are 3.17 Å. Os2- is bonded in a 4-coordinate geometry to four equivalent U4+ and four equivalent Si atoms. All Os–Si bond lengths are 2.40 Å. Si is bonded in a 5-coordinate geometry to four equivalent Os2- and one Si atom. The Si–Si bond length is 2.37 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(CrSi)2 by Materials Project

U(CrSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. U3+ is bonded in a distorted body-centered cubic geometry to eight equivalent Si4- atoms. All U–Si bond lengths are 3.02 Å. Cr+2.50+ is bonded to four equivalent Si4- atoms to form a mixture of corner and edge-sharing CrSi4 tetrahedra. All Cr–Si bond lengths are 2.39 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent U3+, four equivalent Cr+2.50+, and one Si4- atom. The Si–Si bond length is 2.38 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(WO4)2 by Materials Project

U(WO4)2 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. U4+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of U–O bond distances ranging from 2.31–2.46 Å. There are two inequivalent W6+ sites. In the first W6+ site, W6+ is bonded in a tetrahedral geometry to four O2- atoms. There is two shorter (1.81 Å) and two longer (1.82 Å) W–O bond length. In the second W6+ site, W6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of W–O bond distances ranging from 1.81–1.85 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one W6+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one W6+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one W6+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one W6+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one W6+ atom. In the sixth O2- site, O2- is bonded in a distorted linear geometry to one U4+ and one W6+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one W6+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one U4+ and one W6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(IO4)2 by Materials Project

U(O4I)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. U6+ is bonded to eight O2- atoms to form distorted edge-sharing UO8 hexagonal bipyramids. There are a spread of U–O bond distances ranging from 1.82–2.51 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one U6+ and one I5+ atom. The O–I bond length is 2.79 Å. In the second O2- site, O2- is bonded in a 1-coordinate geometry to one U6+ and two equivalent I5+ atoms. There are one shorter (1.86 Å) and one longer (2.55 Å) O–I bond lengths. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent U6+ and one I5+ atom. The O–I bond length is 1.89 Å. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent I5+ atoms. There are one shorter (1.81 Å) and one longer (2.48 Å) O–I bond lengths. I5+ is bonded in a 6-coordinate geometry to six O2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(NiAs)2 by Materials Project

U(NiAs)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. U3+ is bonded in a 8-coordinate geometry to eight As3- atoms. There are four shorter (3.12 Å) and four longer (3.13 Å) U–As bond lengths. There are two inequivalent Ni+1.50+ sites. In the first Ni+1.50+ site, Ni+1.50+ is bonded to four equivalent As3- atoms to form a mixture of edge and corner-sharing NiAs4 tetrahedra. All Ni–As bond lengths are 2.41 Å. In the second Ni+1.50+ site, Ni+1.50+ is bonded in a 5-coordinate geometry to five As3- atoms. There are one shorter (2.30 Å) and four longer (2.35 Å) Ni–As bond lengths. There are two inequivalent As3- sites. In the first As3- site, As3- is bonded in a 4-coordinate geometry to four equivalent U3+ and four equivalent Ni+1.50+ atoms. In the second As3- site, As3- is bonded in a 5-coordinate geometry to four equivalent U3+ and five Ni+1.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(Mo3S4)2 by Materials Project

U(Mo3S4)2 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. U4+ is bonded in a body-centered cubic geometry to eight S2- atoms. There are two shorter (2.74 Å) and six longer (2.94 Å) U–S bond lengths. Mo2+ is bonded to five S2- atoms to form a mixture of edge and corner-sharing MoS5 trigonal bipyramids. There are a spread of Mo–S bond distances ranging from 2.42–2.59 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to one U4+ and three equivalent Mo2+ atoms. In the second S2- site, S2- is bonded in a 5-coordinate geometry to one U4+ and four equivalent Mo2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(CuAs)2 by Materials Project

U(CuAs)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. U4+ is bonded to six equivalent As3- atoms to form UAs6 octahedra that share corners with twelve equivalent CuAs4 tetrahedra, edges with six equivalent UAs6 octahedra, and edges with six equivalent CuAs4 tetrahedra. All U–As bond lengths are 2.88 Å. Cu1+ is bonded to four equivalent As3- atoms to form CuAs4 tetrahedra that share corners with six equivalent UAs6 octahedra, corners with six equivalent CuAs4 tetrahedra, edges with three equivalent UAs6 octahedra, and edges with three equivalent CuAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 18–55°. There are three shorter (2.45 Å) and one longer (2.50 Å) Cu–As bond lengths. As3- is bonded to three equivalent U4+ and four equivalent Cu1+ atoms to form a mixture of distorted corner and edge-sharing AsU3Cu4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(RhO3)2 by Materials Project

U(RhO3)2 is Hydrophilite-derived structured and crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. U6+ is bonded to six O2- atoms to form UO6 octahedra that share corners with eight equivalent RhO6 octahedra and edges with two equivalent RhO6 octahedra. The corner-sharing octahedra tilt angles range from 48–51°. There are four shorter (2.09 Å) and two longer (2.13 Å) U–O bond lengths. Rh3+ is bonded to six O2- atoms to form RhO6 octahedra that share corners with four equivalent UO6 octahedra, corners with four equivalent RhO6 octahedra, an edgeedge with one UO6 octahedra, and an edgeedge with one RhO6 octahedra. The corner-sharing octahedra tilt angles range from 48–51°. There are a spread of Rh–O bond distances ranging from 2.04–2.06 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one U6+ and two equivalent Rh3+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one U6+ and two equivalent Rh3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(SO4)2 by Materials Project

U(SO4)2 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. U4+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of U–O bond distances ranging from 2.32–2.43 Å. There are two inequivalent S6+ sites. In the first S6+ site, S6+ is bonded in a tetrahedral geometry to four O2- atoms. There is two shorter (1.48 Å) and two longer (1.49 Å) S–O bond length. In the second S6+ site, S6+ is bonded in a tetrahedral geometry to four O2- atoms. There is one shorter (1.48 Å) and three longer (1.49 Å) S–O bond length. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one U4+ and one S6+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one S6+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one S6+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one S6+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one U4+ and one S6+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one S6+ atom. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to one U4+ and one S6+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one S6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Identification of the Elusive Methyl-Loss Channel in the Crossed Molecular Beam Study of Gas-Phase Reaction of Dicarbon Molecules (C 2 ; X 1 Σ g + /a 3 Π u ) with 2-Methyl-1,3-butadiene (C 5 H 8 ; X 1 A')

The crossed molecular beams technique was utilized to explore the reaction of dicarbon C 2 (X 1 Σ g + /a 3 Π u ) with 2-methyl-1,3-butadiene (isoprene, CH 2 C(CH 3 )CHCH 2 ; X 1 A') at a collision energy of 28 ± 1 kJ mol⁻¹ using a supersonic dicarbon beam generated via photolysis (248 nm) of helium-seeded tetrachloroethylene (C 2 Cl 4 ). Here, experimental data combined with previous ab initio calculations provide evidence of the detection of the hitherto elusive methyl elimination channels leading to acyclic resonantly stabilized hexatetraenyl radicals: 1,2,4,5-hexatetraen-3-yl (CH 2 CC•CHCCH 2 ) and/or 1,3,4,5-hexatetraen-3-yl (CH 2 CHC•CCCH 2 ). These pathways are exclusive to the singlet potential energy surface, with the reaction initiated by the barrierless addition of dicarbon to one of the carbon-carbon double bonds in the diene. In combustion systems, both hexatetraenyl radicals can isomerize to the phenyl radical (C 6 H 5 ) through a hydrogen atom assisted isomerization – the crucial reaction intermediate and molecular mass growth species step toward the formation of polycyclic aromatic hydrocarbons (PAHs) and soot.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Nonenzymatic RNA copying with a potentially primordial genetic alphabet

Nonenzymatic RNA copying is thought to have been responsible for the replication of genetic information during the origin of life. However, chemical copying with the canonical nucleotides (A, U, G, and C) strongly favors the incorporation of G and C and disfavors the incorporation of A and especially U because of the stronger G:C vs. A:U base pair and the weaker stacking interactions of U. Recent advances in prebiotic chemistry suggest that the 2-thiopyrimidines were precursors to the canonical pyrimidines, raising the possibility that they may have played an important early role in RNA copying chemistry. Furthermore, 2-thiouridine (s 2 U) and inosine (I) form by deamination of 2-thiocytidine (s 2 C) and A, respectively. We used thermodynamic and crystallographic analyses to compare the I:s 2 C and A:s 2 U base pairs. We find that the I:s 2 C base pair is isomorphic and isoenergetic with the A:s 2 U base pair. The I:s 2 C base pair is weaker than a canonical G:C base pair, while the A:s 2 U base pair is stronger than the canonical A:U base pair, so that a genetic alphabet consisting of s 2 U, s 2 C, I, and A generates RNA duplexes with uniform base pairing energies. Consistent with these results, kinetic analysis of nonenzymatic template-directed primer extension reactions reveals that s 2 C and s 2 U substrates bind similarly to I and A in the template, and vice versa. Our work supports the plausibility of a potentially primordial genetic alphabet consisting of s 2 U, s 2 C, I, and A and offers a potential solution to the long-standing problem of biased nucleotide incorporation during nonenzymatic template copying.

Science & Technology - Other Topics↗
NASA NTRS1996

The Dissipation in Laser and in Coherent State

The general process in lasers is defined in the photon number representation d rho(sub n)/dt = mu(sub 0)(u - mu(sub 1) u(exp 2) + mu(sub 2) u(exp 2) + mu(sub 3) u(exp 3)...)rho(sub n), where u is the matrix change operation u rho(sub n) = rho(sub n - 1) - rho(sub n), and mu(sub 1), mu(sub 2),...are the coefficients. In the same way as previous papers, we deduced the generating function G(sub 0)(z,t).

Tan, Weihan↗
DOE OSTI2020

FLAG Review 2019: Flavour Lattice Averaging Group (FLAG)

Abstract We review lattice results related to pion, kaon, D -meson, B -meson, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities. More specifically, we report on the determination of the light-quark masses, the form factor $$f_+(0)$$ f + ( 0 ) arising in the semileptonic $$K \rightarrow \pi $$ K → π transition at zero momentum transfer, as well as the decay constant ratio $$f_K/f_\pi $$ f K / f π and its consequences for the CKM matrix elements $$V_{us}$$ V us and $$V_{ud}$$ V ud . Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of $$SU(2)_L\times SU(2)_R$$ S U ( 2 ) L × S U ( 2 ) R and $$SU(3)_L\times SU(3)_R$$ S U ( 3 ) L × S U ( 3 ) R Chiral Perturbation Theory. We review the determination of the $$B_K$$ B K parameter of neutral kaon mixing as well as the additional four B parameters that arise in theories of physics beyond the Standard Model. For the heavy-quark sector, we provide results for $$m_c$$ m c and $$m_b$$ m b as well as those for D - and B -meson decay constants, form factors, and mixing parameters. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. We review the status of lattice determinations of the strong coupling constant $$\alpha _s$$ α s . Finally, in this review we have added a new section reviewing results for nucleon matrix elements of the axial, scalar and tensor bilinears, both isovector and flavor diagonal.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

FLAG Review 2021

Abstract We review lattice results related to pion, kaon, D -meson, B -meson, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities. More specifically, we report on the determination of the light-quark masses, the form factor $$f_+(0)$$ f + ( 0 ) arising in the semileptonic $$K \rightarrow \pi $$ K → π transition at zero momentum transfer, as well as the decay constant ratio $$f_K/f_\pi $$ f K / f π and its consequences for the CKM matrix elements $$V_{us}$$ V us and $$V_{ud}$$ V ud . Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of $$SU(2)_L\times SU(2)_R$$ S U ( 2 ) L × S U ( 2 ) R and $$SU(3)_L\times SU(3)_R$$ S U ( 3 ) L × S U ( 3 ) R Chiral Perturbation Theory. We review the determination of the $$B_K$$ B K parameter of neutral kaon mixing as well as the additional four B parameters that arise in theories of physics beyond the Standard Model. For the heavy-quark sector, we provide results for $$m_c$$ m c and $$m_b$$ m b as well as those for the decay constants, form factors, and mixing parameters of charmed and bottom mesons and baryons. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. We review the status of lattice determinations of the strong coupling constant $$\alpha _s$$ α s . We consider nucleon matrix elements, and review the determinations of the axial, scalar and tensor bilinears, both isovector and flavor diagonal. Finally, in this review we have added a new section reviewing determinations of scale-setting quantities.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Muon $$\mathbf {g-2}$$, neutralino dark matter and stau NLSP

Abstract We explore the implications of resolving the muon $$g-2$$ g - 2 anomaly in a $$SU(4)_c \times SU(2)_L \times SU(2)_R$$ S U ( 4 ) c × S U ( 2 ) L × S U ( 2 ) R model, where the soft supersymmetry breaking scalar and gaugino masses break the left-right (LR) symmetry. A 2 $$\sigma $$ σ resolution of the anomaly requires relatively light sleptons, chargino and LSP neutralino. The stau turns out to be the NLSP of mass $$m_{\tilde{\tau }}\lesssim 400$$ m τ ~ ≲ 400 GeV, and the sleptons from the first two families can be as heavy as about 800 GeV. The chargino is also required to be lighter than about 600 GeV to accommodate the muon $$g-2$$ g - 2 solutions consistent with the dark matter relic density constraint. The dominant right-handed nature of the light slepton states suppress the sensitivity of possible signals which can be probed in Run3 experiments at the LHC. We also discuss the impact of accommodating the Higgs boson mass and the vacuum stability of the scalar potential for these solutions. Although a light stau can be compatible with the stability of the scalar potential, the Higgs boson mass constraint has a strong impact on the solutions with $$\tan \beta $$ tan β bounded from above, namely $$\tan \beta \lesssim 20$$ tan β ≲ 20 . The Higgsinos are heavier than about 4 TeV, and the LSP neutralino has the correct relic density if it is Bino-like. We identify stau–neutralino coannihilation as the dominant mechanism for realizing the desired dark matter relic density, with sneutrino–neutralino coannihiliation playing a minor role. These bino-like dark matter solutions can yield a spin-independent scattering cross-section on the order of $$10^{-13}$$ 10 - 13 pb which hopefully, can be expected to be tested in the near future.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗