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5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on LiBeB by Materials Project

LiBeB crystallizes in the monoclinic P2_1/m space group. The structure is two-dimensional and consists of one LiBeB sheet oriented in the (0, 0, 1) direction. Li1+ is bonded in a 3-coordinate geometry to three equivalent B3- atoms. There are one shorter (2.28 Å) and two longer (2.33 Å) Li–B bond lengths. Be2+ is bonded to four equivalent B3- atoms to form a mixture of distorted edge and corner-sharing BeB4 tetrahedra. There are a spread of Be–B bond distances ranging from 1.88–1.96 Å. B3- is bonded in a 9-coordinate geometry to three equivalent Li1+, four equivalent Be2+, and two equivalent B3- atoms. Both B–B bond lengths are 1.74 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Materials Data on LiBeB by Materials Project

LiBeB crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of two lithium molecules; two Be2B sheets oriented in the (0, 0, 1) direction; and one LiB sheet oriented in the (0, 0, 1) direction. In each Be2B sheet, there are two inequivalent Be2+ sites. In the first Be2+ site, Be2+ is bonded in a trigonal planar geometry to three equivalent B3- atoms. All Be–B bond lengths are 1.91 Å. In the second Be2+ site, Be2+ is bonded in a distorted trigonal planar geometry to three equivalent B3- atoms. All Be–B bond lengths are 1.94 Å. B3- is bonded in a distorted hexagonal planar geometry to six Be2+ atoms. In the LiB sheet, there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six B3- atoms. All Li–B bond lengths are 2.37 Å. In the second Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six B3- atoms. All Li–B bond lengths are 2.16 Å. There are two inequivalent B3- sites. In the first B3- site, B3- is bonded in a 9-coordinate geometry to six Li1+ and three equivalent B3- atoms. All B–B bond lengths are 1.89 Å. In the second B3- site, B3- is bonded in a 9-coordinate geometry to six Li1+ and three equivalent B3- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Materials Data on LiBeB by Materials Project

LiBeB crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. there are three inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a 1-coordinate geometry to six Be2+ and three B3- atoms. There are a spread of Li–Be bond distances ranging from 2.13–2.18 Å. There are one shorter (2.07 Å) and two longer (2.36 Å) Li–B bond lengths. In the second Li1+ site, Li1+ is bonded in a 4-coordinate geometry to four B3- atoms. There are two shorter (2.20 Å) and two longer (2.27 Å) Li–B bond lengths. In the third Li1+ site, Li1+ is bonded in a 2-coordinate geometry to four Be2+ and three B3- atoms. There are two shorter (2.18 Å) and two longer (2.19 Å) Li–Be bond lengths. There are two shorter (2.08 Å) and one longer (2.28 Å) Li–B bond lengths. There are two inequivalent Be2+ sites. In the first Be2+ site, Be2+ is bonded in a distorted body-centered cubic geometry to four Li1+ and four B3- atoms. There are a spread of Be–B bond distances ranging from 2.06–2.43 Å. In the second Be2+ site, Be2+ is bonded in a distorted body-centered cubic geometry to four Li1+ and four B3- atoms. There are a spread of Be–B bond distances ranging from 2.01–2.22 Å. There are three inequivalent B3- sites. In the first B3- site, B3- is bonded in a 7-coordinate geometry to one Li1+ and six Be2+ atoms. In the second B3- site, B3- is bonded to four Li1+ and two equivalent B3- atoms to form distorted edge-sharing BLi4B2 tetrahedra. Both B–B bond lengths are 2.02 Å. In the third B3- site, B3- is bonded in a 4-coordinate geometry to seven Li1+, four Be2+, and two equivalent B3- atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1997

Issues concerning the Orion gamma ray line observations: Line splitting and LiBeB origin

The phenomenon of broad gamma ray line splitting is discussed, together with a scenario for the suppression of the blue wings of these broad lines due to the geometry of the accelerated particle interaction region. The broad and narrow gamma ray line emissions are compared taking into account the line splitting effect. It is concluded that the observed gamma ray lines from Orion are most likely broad, implying that the low energy cosmic rays which produce this line emission consist mostly of C and heavier ions. The suppression of the proton and alpha particle abundances requires acceleration conditions such as the acceleration of the ejecta of the supernovae before mixing with the interstellar medium. Similar conditions are implied by observations of the B and Be in low metallicity stars formed during the first Gyr of galactic evolution.

Ramaty, R.↗
NASA NTRS1993

Population II Li-6 as a probe of nucleosynthesis and stellar structure and evolution

We discuss the importance of Population II Li-6 as a diagnostic for models of primordial nucleosynthesis, cosmic-ray nucleosyntheses in the early Galaxy, and the structure and evolution of metal-poor solar-type stars. The observation of Li-6 in the subdwarf HD 84937 is shown to be consistent with the existing Population II LiBeB data within the context of a simple three-component model: (1) standard big bang nucleosynthesis, (2) Population II cosmic-ray nucleosynthesis, (3) standard (nonrotating) stellar LiBeB depletion. If this interpretation is correct, we predict a potentially detectable boron abundance for this star: about 2 x 10 exp -12. Subsequent Population II LiBeB observations, and in particular further observations of Population II Li-6, are shown to be crucial to our understanding of the primordial and early galactic creation and destruction mechanisms for light elements.

Steigman, Gary↗