Results for “LiMgPO4”

DOE OSTI2020

Materials Data on LiMgPO4 by Materials Project

LiMgPO4 is Spinel-derived structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with four equivalent MgO6 octahedra, corners with two equivalent PO4 tetrahedra, edges with two equivalent LiO6 octahedra, edges with two equivalent MgO6 octahedra, and edges with two equivalent PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–67°. There are a spread of Li–O bond distances ranging from 2.12–2.19 Å. Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with four equivalent LiO6 octahedra, corners with four equivalent MgO6 octahedra, corners with four equivalent PO4 tetrahedra, edges with two equivalent LiO6 octahedra, and an edgeedge with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–67°. There are a spread of Mg–O bond distances ranging from 2.07–2.19 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent LiO6 octahedra, corners with four equivalent MgO6 octahedra, an edgeedge with one MgO6 octahedra, and edges with two equivalent LiO6 octahedra. The corner-sharing octahedra tilt angles range from 50–58°. There are a spread of P–O bond distances ranging from 1.54–1.57 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Li1+, two equivalent Mg2+, and one P5+ atom. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Li1+, one Mg2+, and one P5+ atom. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent Li1+, one Mg2+, and one P5+ atom.

36 MATERIALS SCIENCE↗

NASA NTRS2002

Phosphorus Equilibria Among Mafic Silicate Phases

Phosphorus incorporation in major rock-forming silicate minerals has the following implications: (1) Reactions between phosphorus-hosting major silicates and accessory phosphates, which are also major trace element carriers, may control the stability of the latter and thus may affect the amount of phosphorus and other trace elements released to the coexisting melt or fluid phase. (2) Less of a phosphate mineral is needed to account for the bulk phosphorus of planetaty mantles. (3) During partial melting of mantle mineral assemblages or equilibrium fractional crystallization of basaltic magmas, and in the absence or prior to saturation with a phosphate mineral, silicate melts may become enriched in phosphorus, especially in the geochemically important low melt fraction regime, Although the small differences in the ionic radii of IVp5+, IVSi4+, and IV Al3+ makes phosphoms incorporation into crystalline silicates perhaps unsurprising, isostructural silicate and phosphate crystalline solids do not readily form solutions, e.g., (Fe, Mg)2SiO4 vs. LiMgPO4, SiO)2 VS. AlPO4. Nonetheless, there are reports of, poorly characterized silico-phosphate phases in angrites , 2-4 wt% P2O5 in olivine and pyroxene grains in pallasites and reduced terestrial basalts which are little understood but potentially useful, and up to 17 wt% P2O5 in olivine from ancient slags. However, such enrichments are rare and only underscore the likelihood of phosphoms incorporation in silicate minerals. The mechanisms that allow phosphorus to enter major rock-forming silicate minerals (e.g., Oliv, Px, Gt) remain little understood and the relevant data base is limited. Nonetheless, old and new high-pressure (5-10 GPa) experimental data suggest that P2O5 wt% decreases from silica-poor to silica-rich compositions or from orthosilicate to chain silicate structures (garnet > olivine > orthopyroxene) which implies that phosphorus incorporation in silicates is perhaps more structure-than site-specific. The data also indicate that DXVliQP2O5 decrease in the same order, but DOVLiQP2O5 and DOpx/LiQP205 are likely constant, respectively equal to 0.08(3) and 0.007(4), in contrast, DG1ILiQP205 increases from 0.15(3) to 0.36(10) as garnet becomes majoritic, thus silica-enriched, and may also depend on liquid composition (SiO2, P2O5 and Na2O wt%).

Berlin, Jana↗