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All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

K and U systematics and average concentrations on the moon

The K-U, Th-U, and Th-Al systematics for lunar samples from the Apollo 11-17 missions and the Luna 16 and 20 missions are summarized. With few exceptions (granitic portion of 12013 and the Apollo 17 mare basalts) the Th/U ratio is 3.8 plus or minus 0.2. The K/U ratio for lunar samples is about 2600 and is distinctly different from the K/U ratio found in terrestrial samples and in the majority of meteorites. The K-U systematics are similar to the K-La, K-Sm, K-Ba, and K-Zr systematics, suggesting that the moon accreted approximately homogeneously. Based on a model the moon contains an average abundance of about 80 ppb U, about 200 ppm K, and about 7 times chondritic abundances for all the refractory elements such as Al, Ca, Ti, Zr, Ba, Sr, and REE. The Th-Al systematics of many lunar highland rocks are dominated by the presence of the rock-type KREEP.

Schonfeld, E.↗
DOE OSTI2020

Materials Data on KLa3 by Materials Project

KLa3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. K is bonded to twelve La atoms to form KLa12 cuboctahedra that share corners with four equivalent KLa12 cuboctahedra, corners with eight equivalent LaK4La8 cuboctahedra, edges with eight equivalent KLa12 cuboctahedra, edges with sixteen equivalent LaK4La8 cuboctahedra, faces with four equivalent KLa12 cuboctahedra, and faces with fourteen LaK4La8 cuboctahedra. There are four shorter (3.84 Å) and eight longer (3.87 Å) K–La bond lengths. There are two inequivalent La sites. In the first La site, La is bonded to four equivalent K and eight La atoms to form LaK4La8 cuboctahedra that share corners with twelve equivalent LaK4La8 cuboctahedra, edges with eight equivalent KLa12 cuboctahedra, edges with sixteen LaK4La8 cuboctahedra, faces with four equivalent KLa12 cuboctahedra, and faces with fourteen LaK4La8 cuboctahedra. There are four shorter (3.84 Å) and four longer (3.87 Å) La–La bond lengths. In the second La site, La is bonded to four equivalent K and eight equivalent La atoms to form LaK4La8 cuboctahedra that share corners with four equivalent LaK4La8 cuboctahedra, corners with eight equivalent KLa12 cuboctahedra, edges with twenty-four LaK4La8 cuboctahedra, faces with six equivalent KLa12 cuboctahedra, and faces with twelve LaK4La8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K5La2 by Materials Project

K5La2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are three inequivalent K sites. In the first K site, K is bonded in a 12-coordinate geometry to six K and six equivalent La atoms. There are a spread of K–K bond distances ranging from 4.16–4.69 Å. There are a spread of K–La bond distances ranging from 4.25–4.79 Å. In the second K site, K is bonded in a 10-coordinate geometry to eight K and two equivalent La atoms. There are a spread of K–K bond distances ranging from 4.20–4.58 Å. Both K–La bond lengths are 4.81 Å. In the third K site, K is bonded in a 9-coordinate geometry to six K and three equivalent La atoms. The K–K bond length is 4.21 Å. There are a spread of K–La bond distances ranging from 4.35–4.61 Å. La is bonded in a 1-coordinate geometry to ten K and one La atom. The La–La bond length is 2.91 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KLa3 by Materials Project

KLa3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. K is bonded to twelve equivalent La atoms to form KLa12 cuboctahedra that share corners with twelve equivalent KLa12 cuboctahedra, edges with twenty-four equivalent LaK4La8 cuboctahedra, faces with six equivalent KLa12 cuboctahedra, and faces with twelve equivalent LaK4La8 cuboctahedra. All K–La bond lengths are 3.86 Å. La is bonded to four equivalent K and eight equivalent La atoms to form LaK4La8 cuboctahedra that share corners with twelve equivalent LaK4La8 cuboctahedra, edges with eight equivalent KLa12 cuboctahedra, edges with sixteen equivalent LaK4La8 cuboctahedra, faces with four equivalent KLa12 cuboctahedra, and faces with fourteen equivalent LaK4La8 cuboctahedra. All La–La bond lengths are 3.86 Å.

36 MATERIALS SCIENCE↗