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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Fe2(PO3)5 by Materials Project

Fe2(PO3)5 crystallizes in the monoclinic Pc space group. The structure is three-dimensional. there are two inequivalent Fe+2.50+ sites. In the first Fe+2.50+ site, Fe+2.50+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six PO4 tetrahedra and an edgeedge with one FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.99–2.23 Å. In the second Fe+2.50+ site, Fe+2.50+ is bonded to six O2- atoms to form distorted FeO6 octahedra that share corners with six PO4 tetrahedra and an edgeedge with one FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.99–2.60 Å. There are five inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two FeO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedral tilt angles are 41°. There are a spread of P–O bond distances ranging from 1.49–1.63 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with three FeO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 16–66°. There are a spread of P–O bond distances ranging from 1.48–1.60 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with three FeO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 23–63°. There are a spread of P–O bond distances ranging from 1.50–1.58 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent FeO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–53°. There are a spread of P–O bond distances ranging from 1.49–1.64 Å. In the fifth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent FeO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–44°. There are a spread of P–O bond distances ranging from 1.50–1.63 Å. There are fifteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Fe+2.50+ and one P5+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe+2.50+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to two Fe+2.50+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Fe+2.50+ and one P5+ atom. In the eighth O2- site, O2- is bonded in a distorted linear geometry to one Fe+2.50+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe+2.50+ and one P5+ atom. In the tenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Fe+2.50+ and one P5+ atom. In the eleventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Fe+2.50+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to two Fe+2.50+ and one P5+ atom. In the thirteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Fe+2.50+ and one P5+ atom. In the fifteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiFe2(PO3)5 by Materials Project

LiFe2(PO3)5 crystallizes in the monoclinic Cc space group. The structure is three-dimensional. Li1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Li–O bond distances ranging from 1.87–2.47 Å. There are two inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to four O2- atoms to form distorted FeO4 trigonal pyramids that share corners with four PO4 tetrahedra and a cornercorner with one FeO4 trigonal pyramid. There are a spread of Fe–O bond distances ranging from 2.00–2.27 Å. In the second Fe2+ site, Fe2+ is bonded to four O2- atoms to form distorted FeO4 trigonal pyramids that share corners with four PO4 tetrahedra and a cornercorner with one FeO4 trigonal pyramid. There are a spread of Fe–O bond distances ranging from 1.95–2.09 Å. There are five inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two PO4 tetrahedra and a cornercorner with one FeO4 trigonal pyramid. There are a spread of P–O bond distances ranging from 1.48–1.64 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two PO4 tetrahedra and corners with two FeO4 trigonal pyramids. There are a spread of P–O bond distances ranging from 1.50–1.61 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two PO4 tetrahedra and a cornercorner with one FeO4 trigonal pyramid. There are a spread of P–O bond distances ranging from 1.48–1.62 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two PO4 tetrahedra and corners with two FeO4 trigonal pyramids. There are a spread of P–O bond distances ranging from 1.47–1.60 Å. In the fifth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two PO4 tetrahedra and corners with two FeO4 trigonal pyramids. There are a spread of P–O bond distances ranging from 1.51–1.60 Å. There are fifteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Li1+ and one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe2+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two P5+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Fe2+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one P5+ atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Li1+ and one P5+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Fe2+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Fe2+ and one P5+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the twelfth O2- site, O2- is bonded in a bent 120 degrees geometry to one Fe2+ and one P5+ atom. In the thirteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two P5+ atoms. In the fourteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Fe2+, and one P5+ atom. In the fifteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Fe2+, and one P5+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS2017

Experimental Study into the Stability of Whitlockite in Basaltic Magmas

Apatite Ca5(PO4)3(F,Cl,OH), merrillite Ca18Na2Mg2(PO4)14, and whitlockite Ca9(Mg,Fe2+)(PO4)6[PO3(OH)] are the primary phosphate minerals found in most planetary materials including rocks from Earth, Moon, Mars, and asteroids [1-2]. For many years, the terms merrillite and whitlockite have been used interchangeably in the meteorite literature. Much of the confusion regarding the relationship between terrestrial and extraterrestrial "whitlockite" is based on the presence or absence of hydrogen in the mineral structure. Whitlockite has approximately 8500 ppm H2O, and the term "merrillite" has been adopted to identify the hydrogen-free form of whitlockite [2]. The atomic structures of merrillite and whitlockite were examined in detail by Hughes et al. [3-4]. On Earth, whitlockite has been found in rocks from evolved pegmatitic systems [2-4] and in some mantle rocks [e.g., 5]. Furthermore, terrestrial whitlockite has been shown to have some merrillite component [4]. For the meteoritic and lunar materials that have been investigated, merrillite appears to be far more common than whitlockite, and it has been proposed that the whitlockite component is unique to terrestrial samples [4]. There are some reports of "whitlockite" in the meteorite literature; however, these likely represent misidentifications of merrillite because there have been no reports of extraterrestrial whitlockite that have been verified through crystal structural studies or analyzed for their H contents. Hughes et al. [3] reported the atomic arrangement of lunar merrillite and demonstrated that the phase is similar to meteoritic merrillite and, predictably, devoid of hydrogen. In a follow-up study, Hughes et al. [4] reported the atomic arrangements of two natural samples of whitlockite, one synthetic whitlockite, and samples of synthetic whitlockite that were heated at 500degC and 1050degC for 24 h. The crystal chemistry and crystal structures of the phases were compared, and it was discovered that the latter treatment resulted in the dehydrogenation of whitlockite to form merrillite. The presence of merrillite vs. whitlockite was widely thought to serve as an indication that magmas were anhydrous [e.g., 6-7]. However, McCubbin et al., [8] determined that merrillite in the martian meteorite Shergotty had no discernible whitlockite component despite its coexistence with OH-rich apatite. Consequently, McCubbin et al., (2014) speculated that the absence of a whitlockite component in Shergotty merrillite and other planetary merrillites may be a consequence of the limited thermal stability of H in whitlockite (stable only at T less than1050degC), which would prohibit merrillite-whitlockite solid-solution at high temperatures. In the present study, we have aimed to test this hypothesis experimentally by examining the stability of whitlockite in basaltic magmas at 1.2 GPa and a temperature range of -1000- 1300degC.

McCubbin, F. M.↗