Results for “PtRh” | Engineering Papers

DOE OSTI2020

Materials Data on PtRh by Materials Project

PtRh is Copper-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Rh sites. In the first Rh site, Rh is bonded to six equivalent Rh and six Pt atoms to form RhPt6Rh6 cuboctahedra that share corners with twelve RhPt6Rh6 cuboctahedra, edges with twelve RhPt6Rh6 cuboctahedra, edges with twelve PtPt6Rh6 cuboctahedra, faces with six equivalent RhPt6Rh6 cuboctahedra, and faces with twelve PtPt6Rh6 cuboctahedra. All Rh–Rh bond lengths are 2.77 Å. All Rh–Pt bond lengths are 2.76 Å. In the second Rh site, Rh is bonded to ten equivalent Rh and six Pt atoms to form RhPt6Rh10 cuboctahedra that share corners with ten PtPt6Rh6 cuboctahedra, corners with twelve RhPt6Rh6 cuboctahedra, edges with eight PtPt6Rh6 cuboctahedra, edges with sixteen RhPt6Rh6 cuboctahedra, faces with sixteen equivalent RhPt6Rh10 cuboctahedra, and faces with eighteen PtPt6Rh6 cuboctahedra. There are a spread of Rh–Rh bond distances ranging from 2.77–5.54 Å. All Rh–Pt bond lengths are 2.76 Å. There are three inequivalent Pt sites. In the first Pt site, Pt is bonded to six equivalent Rh and six equivalent Pt atoms to form PtPt6Rh6 cuboctahedra that share corners with twelve PtPt6Rh6 cuboctahedra, edges with twelve equivalent RhPt6Rh6 cuboctahedra, edges with twelve PtPt6Rh6 cuboctahedra, faces with six equivalent PtPt6Rh6 cuboctahedra, and faces with twelve equivalent RhPt6Rh6 cuboctahedra. All Pt–Pt bond lengths are 2.77 Å. In the second Pt site, Pt is bonded to six Rh and six equivalent Pt atoms to form PtPt6Rh6 cuboctahedra that share corners with five equivalent RhPt6Rh10 cuboctahedra, corners with twelve PtPt6Rh6 cuboctahedra, edges with ten RhPt6Rh6 cuboctahedra, edges with twelve PtPt6Rh6 cuboctahedra, faces with six equivalent PtPt6Rh6 cuboctahedra, and faces with fifteen RhPt6Rh6 cuboctahedra. All Pt–Rh bond lengths are 2.76 Å. All Pt–Pt bond lengths are 2.77 Å. In the third Pt site, Pt is bonded to six Rh and six equivalent Pt atoms to form PtPt6Rh6 cuboctahedra that share corners with five equivalent RhPt6Rh10 cuboctahedra, corners with twelve PtPt6Rh6 cuboctahedra, edges with ten RhPt6Rh6 cuboctahedra, edges with twelve PtPt6Rh6 cuboctahedra, faces with six equivalent PtPt6Rh6 cuboctahedra, and faces with fifteen RhPt6Rh6 cuboctahedra. All Pt–Pt bond lengths are 2.77 Å.

36 MATERIALS SCIENCE↗

NASA NTRS1994

Partial melting of the St. Severin (LL) and Lost City (H) ordinary chondrites: One step backwards and two steps forward

This study looks at partial melting in H and LL chondrites at nearly one atmosphere of total pressure as part of a continuing study of the origins of basaltic achondrites. Previously, melting experiments on anhydrous CM and CV chondrites showed that, near its solidus, the CM chondrite produced melts having major element chemistries similar to the Sioux County eucrite; but, the pyroxenes in the residuum were too iron-rich to form diogenites. Our preliminary results from melting experiments on ordinary (H, LL) chondrites suggested that, although the melts did not look like any known eucrites, pyroxenes from these charges bracketed the compositional range of pyroxenes found in diogenites. We had used the Fe/Mg exchange coefficients calculated for olivine, pyroxene, and melt in these charges to evaluate the approach to equilibrium, which appeared to be excellent. Unfortunately, mass balance calculations later indicated to us that, unlike our CM and CV charges, the LL and H experimental charges had lost significant amounts of iron to their (Pt or PtRh) supports. Apparently, pyroxene stability in chondritic systems is quite sensitive to the amount of FeO, and it was this unrecognized change in the bulk iron content which had stabilized the high temperature, highly magnesian pyroxenes. Accordingly, this work reinvestigates the phase equilibria of ordinary chondrites, eliminating iron and nickel loss, and reports significant differences. It also looks closely at how the iron and sodium in the bulk charge affect the stability of pyroxene, and it comments on how these new results apply to the problems of diogenite and eucrite petrogenesis.

Jurewicz, A. J. G.↗