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All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Petrology of Amoeboid Olivine Aggregates in Antarctic CR Chondrites: Comparison With Other Carbonaceous Chondrites

Amoeboid olivine aggregates (AOAs) are important refractory components of carbonaceous chondrites and have been interpreted to represent solar nebular condensates that experienced high-temperature annealing, but largely escaped melting. In addition, because AOAs in primitive chondrites are composed of fine-grained minerals (forsterite, anorthite, spinel) that are easily modified during post crystallization alteration, the mineralogy of AOAs can be used as a sensitive indicator of metamorphic or alteration processes. AOAs in CR chondrites are particularly important because they show little evidence for secondary alteration. In addition, some CR AOAs contain Mn-enriched forsterite (aka low-iron, Mn-enriched or LIME olivine), which is an indicator of nebular formation conditions. Here we report preliminary results of the mineralogy and petrology of AOAs in Antarctic CR chondrites, and compare them to those in other carbonaceous chondrites.

Komatsu, M.↗
NASA NTRS2016

The Cr Redox Record of fO2 Variation in Angrites. Evidence for Redox Conditions of Angrite Petrogenesis and Parent Body

Angrites represent some of the earliest stages of planetesimal differentiation. Not surprisingly, there is no simple petrogenetic model for their origin. Petrogenesis has been linked to both magmatic and impact processes. Studies demonstrated that melting of chondritic material (e.g. CM, CV) at redox conditions where pure iron metal is unstable (e.g., IW+1 to IW+2) produced angrite-like melts. Alternatively, angrites were produced at more reducing conditions (<IW) with their exotic melt compositions resulting from carbonates in the source or from nebular condensation. Clearly, understanding what role fO2 plays in producing angrite magmas is critical for deciphering their petrogenesis and extending our understanding of primordial melting of asteroids. Calculations for the fO2 conditions of angrite crystallization are limited, and only preliminary attempts been made to understand the changes in fO2 that occurred during petrogenesis. Many of the angrites have phase assemblages which provide conflicting signals about redox conditions during crystallization (e.g., Fe metal and a Fe-Ti oxide with potential Fe3+. There have been several estimates of fO2 for angrites. Most notably, experiments examined the variation of DEu/DGd with fO2, between plagioclase and fassaitic pyroxene in equilibrium with an angrite melt composition. They used their observations to estimate the fO2 of crystallization to be approximately IW+0.6 for angrite LEW 86010. This estimate is only a "snapshot" of fO2 conditions during co-crystallization of plagioclase and pyroxene. Preliminary XANES analyses of V redox state in pyroxenes from D'Orbigny reported changes in fO2 from IW-0.7 during early pyroxene crystallization to IW+0.5 during latter episodes of pyroxene crystallization [15]. As this was a preliminary report, it presented limited information concerning the effects of pyroxene orientation and composition on the V valence measurements, and the effect of melt composition on valence and partitioning behavior of V. A closer examination of fO2 as recorded by Cr valence state in olivine will allow us to test models for primordial melting of chondritic material to produce the angrite parent melts. Here, we report the our initial stages of examining the origin and conditions of primordial melting on the angrite parent body and test some of the above models by integrating an experimental study of Cr and V valence partitioning between olivine [OL] and an angrite melt, with micro-scale determinations of Cr and V oxidation state in OL in selected "volcanic" angrites.

Shearer, Charles K.↗
NASA NTRS2016

Temperature Mapping of Air Film-Cooled Thermal Barrier Coated Surfaces Using Cr-Doped GdAlO3 Phosphor Thermography

It has been recently shown that the high luminescence intensity from a Cr-doped GdAlO3 (Cr:GdAlO3) thermographic phosphor enables non-rastered full-field temperature mapping of thermal barrier coating (TBC) surfaces to temperatures above 1000C. In this presentation, temperature mapping by Cr:GdAlO3 based phosphor thermometry of air film-cooled TBC-coated surfaces is demonstrated for both scaled-up cooling hole geometries as well as for actual components in a burner rig test environment. The effects of thermal background radiation and flame chemiluminescence on the measurements are investigated, and advantages of this method over infrared thermography as well as the limitations of this method for studying air film cooling are discussed.

thermographic phoshor↗
NASA NTRS2017

Valence State Partitioning of Cr and V Between Olivine-Melt and Pyroxene-Melt in Experimental Basalts of a Eucritic Composition

The partitioning of multivalent elements in basaltic systems can elucidate the oxygen fugacity (fO2) conditions under which basalts formed on planetary bodies (Earth, Moon, Mars, asteroids). Chromium and V are minor and trace elements in basaltic melts, partition into several minerals that crystallize from basaltic melts, exist in multiple valence states at differing fO2 conditions, and can therefore be used as oxybarometers for basaltic melts. Chromium is mostly 3+ in terrestrial basaltic melts at relatively high fO2 values (≥ IW+3.5), and mostly 2+ in melts at low fO2 values (≤ IW-1), such as those on the Moon and some asteroids. At intermediate fO2s, (i.e., IW-1 to IW+3.5), basaltic melts contain both Cr3+ and Cr2+. Vanadium in basaltic melts is mostly 4+ at high fO2, mostly 3+ at low fO2, and a mix of V3+ and V4+ at intermediate fO2 con-ditions. Understanding the partitioning of Cr and V into silicate phases with changing fO2 is therefore critical to the employment of Cr and V oxybarometers. In this abstract we examine the equilibrium partitioning of Cr and V between olivine/melt and pyroxene/melt in experimental charges of a eucritic composition produced at differing fO2 conditions. This study will add to the experimental data on DCr and DV (i.e., olivine/melt, pyroxene/melt) at differing fO2, and in turn these D values will be used to assess the fO2 of eucrite basalts and perhaps other compositionally similar planetary basalts.

Karner, J. M.↗
NASA NTRS2017

Petrology of Amoeboid Olivine Aggregates in Antarctic CR Chondrites: Evidence for Aqueous Alteration and Shock Metamorphism

CR chondrites are the group of carbonaceous chondrites that preserve records of formation of their components in the solar nebula. Although they are affected by aqueous alteration, many chondrules and CAIs are well-preserved, suggesting they have experienced little thermal metamorphism. We have been investigating the petrologic variations among the CR chondrites in Japanese-NIPR Antarctic meteorite collection. Especially we focused on the petrology of amoeboid olivine aggregates (AOAs) in order to understand secondary alteration on CR chondrite parent body. AOAs are composed of fine-grained forsteritic olivine and refractory minerals formed by condensation from solar nebula, and can be used as sensitive indicators of secondary alteration processes.

Komatsu, M.↗
NASA NTRS2018

Aqueous Alteration and Shock Metamorphism of Antarctic CR Chondrites

CR chondrites are the group of carbonaceous chondrites that best preserve records of formation of their components in the solar nebula. Although they are affected by aqueous alteration, many chondrules and CAIs are well-preserved, suggesting they have experienced little thermal metamorphism. We have been investigating the petrologic variations among the CR chondrites in the NIPR Antarctic meteorite collection. We focused particular attention on the petrology of amoeboid olivine aggregates (AOAs) in order to understand secondary alteration on the CR chondrite parent body. AOAs are composed of fine-grained forsteritic olivine and refractory minerals formed by condensation in the solar nebula, and can be used as sensitive indicators of secondary alteration processes.

Komatsu, M.↗
DOE OSTI2022

Catalyst comprising Pt, Ni, and Cr

Catalysts comprising nanostructured elements comprising microstructured whiskers having an outer surface at least partially covered by a catalyst material comprising at least 90 atomic percent collectively Pt, Ni, and Cr, wherein the Pt is present in a range from 32.4 to 35.8 atomic percent, the Ni is present in a range from 57.7 to 63.7 atomic percent, and the Cr is present in a range from 0.5 to 10.0 atomic percent, and wherein the total atomic percent of Pt, Ni, and Cr equals 100. Catalyst described herein are useful, for example, in fuel cell membrane electrode assemblies.

Steinbach, Andrew J. L.↗
DOE OSTI2020

Materials Data on Cr(PO3)4 by Materials Project

Cr(PO3)4 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Cr4+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Cr–O bond distances ranging from 1.96–2.01 Å. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent CrO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 43–47°. There are a spread of P–O bond distances ranging from 1.50–1.60 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CrO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedral tilt angles are 42°. There are a spread of P–O bond distances ranging from 1.49–1.62 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cr4+ and one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent P5+ atoms. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cr4+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent P5+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cr4+ 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 120 degrees geometry to two P5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(PO3)4 by Materials Project

Cr(PO3)4 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. Cr4+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Cr–O bond distances ranging from 1.91–2.00 Å. There are four inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CrO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedral tilt angles are 40°. There are a spread of P–O bond distances ranging from 1.47–1.63 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent CrO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 43–49°. There are a spread of P–O bond distances ranging from 1.50–1.60 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent CrO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 44–49°. There are a spread of P–O bond distances ranging from 1.51–1.60 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CrO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedral tilt angles are 47°. There are a spread of P–O bond distances ranging from 1.48–1.63 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cr4+ 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 two P5+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 120 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 single-bond geometry to one P5+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cr4+ and one P5+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cr4+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cr4+ and one P5+ atom. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr4+ and one P5+ atom. In the eleventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cr4+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a single-bond geometry to one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(FeSe2)2 by Materials Project

Cr(FeSe2)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Cr3+ is bonded to six Se2- atoms to form CrSe6 octahedra that share corners with twelve equivalent FeSe6 octahedra, edges with two equivalent CrSe6 octahedra, and faces with two equivalent FeSe6 octahedra. The corner-sharing octahedra tilt angles range from 53–56°. There are two shorter (2.53 Å) and four longer (2.56 Å) Cr–Se bond lengths. Fe+2.50+ is bonded to six Se2- atoms to form FeSe6 octahedra that share corners with six equivalent CrSe6 octahedra, edges with six equivalent FeSe6 octahedra, and a faceface with one CrSe6 octahedra. The corner-sharing octahedra tilt angles range from 53–56°. There are a spread of Fe–Se bond distances ranging from 2.40–2.67 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent Cr3+ and three equivalent Fe+2.50+ atoms. In the second Se2- site, Se2- is bonded in a 4-coordinate geometry to one Cr3+ and three equivalent Fe+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(GaS2)2 by Materials Project

Cr(GaS2)2 is Spinel structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Cr2+ is bonded to four equivalent S2- atoms to form CrS4 tetrahedra that share corners with twelve equivalent GaS6 octahedra. The corner-sharing octahedral tilt angles are 55°. All Cr–S bond lengths are 2.19 Å. Ga3+ is bonded to six equivalent S2- atoms to form GaS6 octahedra that share corners with six equivalent CrS4 tetrahedra and edges with six equivalent GaS6 octahedra. All Ga–S bond lengths are 2.53 Å. S2- is bonded in a distorted rectangular see-saw-like geometry to one Cr2+ and three equivalent Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(FeSe2)2 by Materials Project

Cr(FeSe2)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. Cr3+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of Cr–Se bond distances ranging from 2.45–2.51 Å. There are two inequivalent Fe+2.50+ sites. In the first Fe+2.50+ site, Fe+2.50+ is bonded in a distorted pentagonal planar geometry to five Se2- atoms. There are a spread of Fe–Se bond distances ranging from 2.36–2.50 Å. In the second Fe+2.50+ site, Fe+2.50+ is bonded in a distorted pentagonal planar geometry to five Se2- atoms. There are a spread of Fe–Se bond distances ranging from 2.35–2.57 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to one Cr3+ and two Fe+2.50+ atoms. In the second Se2- site, Se2- is bonded to one Cr3+ and three Fe+2.50+ atoms to form a mixture of distorted edge and corner-sharing SeCrFe3 tetrahedra. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to one Cr3+ and two Fe+2.50+ atoms. In the fourth Se2- site, Se2- is bonded to one Cr3+ and three Fe+2.50+ atoms to form a mixture of distorted edge and corner-sharing SeCrFe3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(InS2)2 by Materials Project

Cr(InS2)2 is Spinel-like structured and crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Cr2+ is bonded to six S2- atoms to form CrS6 octahedra that share corners with six equivalent InS4 tetrahedra, edges with two equivalent CrS6 octahedra, and edges with four equivalent InS6 octahedra. There are two shorter (2.45 Å) and four longer (2.48 Å) Cr–S bond lengths. There are two inequivalent In3+ sites. In the first In3+ site, In3+ is bonded to four S2- atoms to form InS4 tetrahedra that share corners with six equivalent CrS6 octahedra and corners with six equivalent InS6 octahedra. The corner-sharing octahedra tilt angles range from 52–67°. There are two shorter (2.58 Å) and two longer (2.60 Å) In–S bond lengths. In the second In3+ site, In3+ is bonded to six S2- atoms to form InS6 octahedra that share corners with six equivalent InS4 tetrahedra, edges with two equivalent InS6 octahedra, and edges with four equivalent CrS6 octahedra. All In–S bond lengths are 2.65 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to one Cr2+ and three In3+ atoms. In the second S2- site, S2- is bonded to two equivalent Cr2+ and two In3+ atoms to form a mixture of distorted corner and edge-sharing SCr2In2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(PO3)4 by Materials Project

Cr(PO3)4 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Cr4+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six PO4 tetrahedra. There is two shorter (1.98 Å) and four longer (2.00 Å) Cr–O bond length. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CrO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 50°. 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 two equivalent CrO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 28–50°. There is two shorter (1.50 Å) and two longer (1.61 Å) P–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cr4+ and one P5+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cr4+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. 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 one Cr4+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(PO3)4 by Materials Project

Cr(PO3)4 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. Cr4+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Cr–O bond distances ranging from 1.92–1.99 Å. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent CrO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 44–45°. There are a spread of P–O bond distances ranging from 1.51–1.59 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CrO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 39°. There are a spread of P–O bond distances ranging from 1.47–1.63 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two P5+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr4+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cr4+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cr4+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(GeO3)2 by Materials Project

Cr(GeO3)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Cr4+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six equivalent GeO4 tetrahedra and edges with two equivalent CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 1.85–2.08 Å. Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with three equivalent CrO6 octahedra and corners with two equivalent GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 41–60°. There are a spread of Ge–O bond distances ranging from 1.75–1.79 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ge4+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr4+ and one Ge4+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Cr4+ and one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(GeO3)2 by Materials Project

Cr(GeO3)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Cr4+ is bonded to six O2- atoms to form distorted CrO6 octahedra that share corners with three equivalent GeO4 tetrahedra, corners with two equivalent GeO5 trigonal bipyramids, edges with two equivalent CrO6 octahedra, and an edgeedge with one GeO5 trigonal bipyramid. There are a spread of Cr–O bond distances ranging from 1.82–2.10 Å. There are two inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with three equivalent CrO6 octahedra and corners with two equivalent GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–60°. There are a spread of Ge–O bond distances ranging from 1.75–1.79 Å. In the second Ge4+ site, Ge4+ is bonded to five O2- atoms to form distorted GeO5 trigonal bipyramids that share corners with two equivalent CrO6 octahedra, corners with two equivalent GeO5 trigonal bipyramids, an edgeedge with one CrO6 octahedra, and an edgeedge with one GeO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 36–41°. There are a spread of Ge–O bond distances ranging from 1.76–2.05 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two equivalent Cr4+ and one Ge4+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent Ge4+ atoms. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent Ge4+ atoms. In the fourth O2- site, O2- is bonded in a distorted T-shaped geometry to one Cr4+ and two equivalent Ge4+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr4+ and one Ge4+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Cr4+ and one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(InS2)2 by Materials Project

Cr(InS2)2 is Spinel structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Cr2+ is bonded to four equivalent S2- atoms to form CrS4 tetrahedra that share corners with twelve equivalent InS6 octahedra. The corner-sharing octahedral tilt angles are 56°. All Cr–S bond lengths are 2.39 Å. In3+ is bonded to six equivalent S2- atoms to form InS6 octahedra that share corners with six equivalent CrS4 tetrahedra and edges with six equivalent InS6 octahedra. All In–S bond lengths are 2.66 Å. S2- is bonded in a distorted rectangular see-saw-like geometry to one Cr2+ and three equivalent In3+ atoms.

36 MATERIALS SCIENCE↗