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Materials Data on BaCr2PO11 by Materials Project

BaCr2PO11 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one BaCr2PO11 sheet oriented in the (0, 0, 1) direction. Ba is bonded in a 10-coordinate geometry to ten O atoms. There are a spread of Ba–O bond distances ranging from 2.75–3.12 Å. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share a cornercorner with one PO4 tetrahedra. There are a spread of Cr–O bond distances ranging from 1.61–1.84 Å. In the second Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share a cornercorner with one PO4 tetrahedra. There are a spread of Cr–O bond distances ranging from 1.60–1.83 Å. P is bonded to four O atoms to form PO4 tetrahedra that share corners with two CrO4 tetrahedra. There is two shorter (1.53 Å) and two longer (1.56 Å) P–O bond length. There are eleven inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Cr atom. In the second O site, O is bonded in a distorted single-bond geometry to two equivalent Ba and one Cr atom. In the third O site, O is bonded in a distorted single-bond geometry to one Ba and one Cr atom. In the fourth O site, O is bonded in a bent 150 degrees geometry to one Cr and one P atom. In the fifth O site, O is bonded in a single-bond geometry to one Ba and one P atom. In the sixth O site, O is bonded in a distorted single-bond geometry to two equivalent Ba and one P atom. In the seventh O site, O is bonded in a distorted bent 120 degrees geometry to one Cr and one P atom. In the eighth O site, O is bonded in a distorted single-bond geometry to two equivalent Ba and one Cr atom. In the ninth O site, O is bonded in a distorted single-bond geometry to one Ba and one Cr atom. In the tenth O site, O is bonded in a single-bond geometry to one Cr atom. In the eleventh O site, O is bonded in a single-bond geometry to one Ba atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb2U2Cr2O15F2 by Materials Project

(RbUCrO7F)4O2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of two hydrogen peroxide molecules and one RbUCrO7F framework. In the RbUCrO7F framework, there are two inequivalent Rb sites. In the first Rb site, Rb is bonded in a 7-coordinate geometry to six O and one F atom. There are a spread of Rb–O bond distances ranging from 2.92–3.45 Å. The Rb–F bond length is 2.99 Å. In the second Rb site, Rb is bonded in a 8-coordinate geometry to seven O and one F atom. There are a spread of Rb–O bond distances ranging from 2.98–3.36 Å. The Rb–F bond length is 3.17 Å. There are two inequivalent U sites. In the first U site, U is bonded to five O and two F atoms to form UO5F2 pentagonal bipyramids that share corners with three CrO4 tetrahedra and an edgeedge with one UO5F2 pentagonal bipyramid. There are a spread of U–O bond distances ranging from 1.81–2.35 Å. Both U–F bond lengths are 2.37 Å. In the second U site, U is bonded to five O and two F atoms to form UO5F2 pentagonal bipyramids that share corners with three CrO4 tetrahedra and an edgeedge with one UO5F2 pentagonal bipyramid. There are a spread of U–O bond distances ranging from 1.82–2.36 Å. There are one shorter (2.34 Å) and one longer (2.37 Å) U–F bond lengths. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share corners with three UO5F2 pentagonal bipyramids. There are a spread of Cr–O bond distances ranging from 1.62–1.69 Å. In the second Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share corners with three UO5F2 pentagonal bipyramids. There are a spread of Cr–O bond distances ranging from 1.62–1.70 Å. There are fourteen inequivalent O sites. In the first O site, O is bonded in a distorted single-bond geometry to two equivalent Rb and one U atom. In the second O site, O is bonded in a single-bond geometry to one Rb and one U atom. In the third O site, O is bonded in a single-bond geometry to one Rb and one U atom. In the fourth O site, O is bonded in a distorted single-bond geometry to two equivalent Rb and one U atom. In the fifth O site, O is bonded in a 1-coordinate geometry to one Rb, one U, and one Cr atom. In the sixth O site, O is bonded in a bent 150 degrees geometry to one U and one Cr atom. In the seventh O site, O is bonded in a distorted linear geometry to one U and one Cr atom. In the eighth O site, O is bonded in a distorted single-bond geometry to two equivalent Rb and one Cr atom. In the ninth O site, O is bonded in a distorted bent 150 degrees geometry to one U and one Cr atom. In the tenth O site, O is bonded in a 1-coordinate geometry to one Rb, one U, and one Cr atom. In the eleventh O site, O is bonded in a distorted linear geometry to one U and one Cr atom. In the twelfth O site, O is bonded in a distorted single-bond geometry to two equivalent Rb and one Cr atom. In the thirteenth O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.23 Å. In the fourteenth O site, O is bonded in a distorted bent 120 degrees geometry to one Rb and one O atom. There are two inequivalent F sites. In the first F site, F is bonded in a distorted trigonal non-coplanar geometry to one Rb and two U atoms. In the second F site, F is bonded in a trigonal non-coplanar geometry to one Rb and two U atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrLa3Cr4O12 by Materials Project

SrLa3Cr4O12 is Orthorhombic Perovskite-derived structured and crystallizes in the monoclinic P2 space group. The structure is three-dimensional. Sr2+ is bonded in a 12-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.51–2.84 Å. There are three inequivalent La3+ sites. In the first La3+ site, La3+ is bonded in a 3-coordinate geometry to nine O2- atoms. There are a spread of La–O bond distances ranging from 2.44–2.79 Å. In the second La3+ site, La3+ is bonded in a 3-coordinate geometry to nine O2- atoms. There are a spread of La–O bond distances ranging from 2.41–2.79 Å. In the third La3+ site, La3+ is bonded in a 3-coordinate geometry to nine O2- atoms. There are a spread of La–O bond distances ranging from 2.43–2.79 Å. There are two inequivalent Cr+3.25+ sites. In the first Cr+3.25+ site, Cr+3.25+ is bonded to six O2- atoms to form corner-sharing CrO6 octahedra. The corner-sharing octahedra tilt angles range from 15–22°. There are a spread of Cr–O bond distances ranging from 1.98–2.01 Å. In the second Cr+3.25+ site, Cr+3.25+ is bonded to six O2- atoms to form corner-sharing CrO6 octahedra. The corner-sharing octahedra tilt angles range from 15–22°. There are a spread of Cr–O bond distances ranging from 1.96–2.00 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to three La3+ and two Cr+3.25+ atoms. In the second O2- site, O2- is bonded in a 5-coordinate geometry to one Sr2+, two La3+, and two Cr+3.25+ atoms. In the third O2- site, O2- is bonded in a 5-coordinate geometry to three La3+ and two equivalent Cr+3.25+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Sr2+, two equivalent La3+, and two equivalent Cr+3.25+ atoms. In the fifth O2- site, O2- is bonded in a 5-coordinate geometry to one Sr2+, two La3+, and two Cr+3.25+ atoms. In the sixth O2- site, O2- is bonded in a 5-coordinate geometry to one Sr2+, two La3+, and two Cr+3.25+ atoms. In the seventh O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Sr2+, one La3+, and two equivalent Cr+3.25+ atoms. In the eighth O2- site, O2- is bonded in a 5-coordinate geometry to three La3+ and two equivalent Cr+3.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on YbCrO5 by Materials Project

YbCrO5 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Yb sites. In the first Yb site, Yb is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Yb–O bond distances ranging from 2.31–2.67 Å. In the second Yb site, Yb is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Yb–O bond distances ranging from 2.29–2.52 Å. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded in a tetrahedral geometry to four O atoms. There are a spread of Cr–O bond distances ranging from 1.64–1.71 Å. In the second Cr site, Cr is bonded in a tetrahedral geometry to four O atoms. There are a spread of Cr–O bond distances ranging from 1.64–1.70 Å. There are ten inequivalent O sites. In the first O site, O is bonded in a distorted bent 150 degrees geometry to one Yb and one Cr atom. In the second O site, O is bonded in a 1-coordinate geometry to two Yb and one Cr atom. In the third O site, O is bonded in a distorted bent 150 degrees geometry to one Yb and one Cr atom. In the fourth O site, O is bonded in a bent 150 degrees geometry to one Yb and one Cr atom. In the fifth O site, O is bonded in a 1-coordinate geometry to two Yb and one Cr atom. In the sixth O site, O is bonded in a distorted trigonal non-coplanar geometry to three Yb atoms. In the seventh O site, O is bonded in a bent 150 degrees geometry to one Yb and one Cr atom. In the eighth O site, O is bonded in a distorted trigonal planar geometry to three Yb atoms. In the ninth O site, O is bonded in a bent 150 degrees geometry to one Yb and one Cr atom. In the tenth O site, O is bonded in a bent 150 degrees geometry to one Yb and one Cr atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on V4(CrS2)5 by Materials Project

V4(CrS2)5 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent V2+ sites. In the first V2+ site, V2+ is bonded to six S2- atoms to form VS6 octahedra that share corners with twelve CrS6 octahedra, edges with five VS6 octahedra, and faces with two CrS6 octahedra. The corner-sharing octahedra tilt angles range from 42–52°. There are a spread of V–S bond distances ranging from 2.41–2.45 Å. In the second V2+ site, V2+ is bonded to six S2- atoms to form VS6 octahedra that share corners with twelve CrS6 octahedra, edges with four VS6 octahedra, and faces with two CrS6 octahedra. The corner-sharing octahedra tilt angles range from 43–53°. There are a spread of V–S bond distances ranging from 2.41–2.51 Å. There are three inequivalent Cr+2.40+ sites. In the first Cr+2.40+ site, Cr+2.40+ is bonded to six S2- atoms to form CrS6 octahedra that share corners with eleven VS6 octahedra, edges with six CrS6 octahedra, and a faceface with one VS6 octahedra. The corner-sharing octahedra tilt angles range from 42–52°. There are a spread of Cr–S bond distances ranging from 2.36–2.45 Å. In the second Cr+2.40+ site, Cr+2.40+ is bonded to six S2- atoms to form CrS6 octahedra that share corners with nine VS6 octahedra, edges with six CrS6 octahedra, and faces with two VS6 octahedra. The corner-sharing octahedra tilt angles range from 47–53°. There are a spread of Cr–S bond distances ranging from 2.38–2.46 Å. In the third Cr+2.40+ site, Cr+2.40+ is bonded to six S2- atoms to form CrS6 octahedra that share corners with eight VS6 octahedra, edges with six CrS6 octahedra, and faces with two equivalent VS6 octahedra. The corner-sharing octahedra tilt angles range from 43–52°. There are a spread of Cr–S bond distances ranging from 2.41–2.46 Å. There are five inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent V2+ and three Cr+2.40+ atoms to form distorted SV2Cr3 square pyramids that share corners with three SV3Cr3 pentagonal pyramids, corners with four SV2Cr3 square pyramids, corners with two equivalent SV2Cr3 trigonal bipyramids, edges with four SV3Cr3 pentagonal pyramids, edges with two SV2Cr3 square pyramids, and edges with two equivalent SV2Cr3 trigonal bipyramids. In the second S2- site, S2- is bonded to three V2+ and three Cr+2.40+ atoms to form distorted SV3Cr3 pentagonal pyramids that share corners with two equivalent SV3Cr3 pentagonal pyramids, corners with three SV2Cr3 square pyramids, a cornercorner with one SV2Cr3 trigonal bipyramid, edges with five SV3Cr3 pentagonal pyramids, edges with five SV2Cr3 square pyramids, and edges with two equivalent SV2Cr3 trigonal bipyramids. In the third S2- site, S2- is bonded to two V2+ and three Cr+2.40+ atoms to form distorted SV2Cr3 square pyramids that share corners with two equivalent SV3Cr3 pentagonal pyramids, corners with three equivalent SV2Cr3 square pyramids, corners with four equivalent SV2Cr3 trigonal bipyramids, edges with six SV3Cr3 pentagonal pyramids, and edges with two SV2Cr3 square pyramids. In the fourth S2- site, S2- is bonded to three V2+ and three Cr+2.40+ atoms to form distorted SV3Cr3 pentagonal pyramids that share corners with three SV3Cr3 pentagonal pyramids, corners with two equivalent SV2Cr3 square pyramids, a cornercorner with one SV2Cr3 trigonal bipyramid, edges with four SV3Cr3 pentagonal pyramids, edges with five SV2Cr3 square pyramids, and edges with three equivalent SV2Cr3 trigonal bipyramids. In the fifth S2- site, S2- is bonded to two V2+ and three Cr+2.40+ atoms to form distorted SV2Cr3 trigonal bipyramids that share corners with two SV3Cr3 pentagonal pyramids, corners with six SV2Cr3 square pyramids, a cornercorner with one SV2Cr3 trigonal bipyramid, edges with five SV3Cr3 pentagonal pyramids, edges with two equivalent SV2Cr3 square pyramids, and an edgeedge with one SV2Cr3 trigonal bipyramid.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrU2Cr2O22 by Materials Project

(SrU2Cr2O15)2(O2)7 crystallizes in the triclinic P-1 space group. The structure is three-dimensional and consists of four hydrogen peroxide molecules, two trioxidane molecules, and one SrU2Cr2O15 framework. In the SrU2Cr2O15 framework, Sr is bonded in a 5-coordinate geometry to five O atoms. There are a spread of Sr–O bond distances ranging from 2.48–2.73 Å. There are two inequivalent U sites. In the first U site, U is bonded to seven O atoms to form distorted UO7 pentagonal bipyramids that share corners with three CrO4 tetrahedra and an edgeedge with one UO7 pentagonal bipyramid. There are a spread of U–O bond distances ranging from 1.82–2.59 Å. In the second U site, U is bonded to seven O atoms to form distorted UO7 pentagonal bipyramids that share corners with three CrO4 tetrahedra and an edgeedge with one UO7 pentagonal bipyramid. There are a spread of U–O bond distances ranging from 1.82–2.59 Å. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share corners with three UO7 pentagonal bipyramids. There are a spread of Cr–O bond distances ranging from 1.65–1.70 Å. In the second Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share corners with three UO7 pentagonal bipyramids. There is three shorter (1.63 Å) and one longer (1.92 Å) Cr–O bond length. There are fifteen inequivalent O sites. In the first O site, O is bonded in a distorted bent 150 degrees geometry to one U and one Cr atom. In the second O site, O is bonded in a 1-coordinate geometry to one Sr, one U, and one Cr atom. In the third O site, O is bonded in a distorted bent 120 degrees geometry to one Sr and one Cr atom. In the fourth O site, O is bonded in a bent 120 degrees geometry to one Sr and one O atom. The O–O bond length is 1.31 Å. In the fifth O site, O is bonded in a distorted linear geometry to one Sr and one U atom. In the sixth O site, O is bonded in a single-bond geometry to one U atom. In the seventh O site, O is bonded in a bent 120 degrees geometry to one Sr and one U atom. In the eighth O site, O is bonded in a single-bond geometry to one U atom. In the ninth O site, O is bonded in a water-like geometry to two equivalent U atoms. In the tenth O site, O is bonded in a water-like geometry to two equivalent U atoms. In the eleventh O site, O is bonded in a distorted single-bond geometry to one U and one Cr atom. In the twelfth O site, O is bonded in a distorted single-bond geometry to one U and one Cr atom. In the thirteenth O site, O is bonded in a distorted bent 120 degrees geometry to one Cr and one O atom. In the fourteenth O site, O is bonded in a distorted single-bond geometry to one U and one Cr atom. In the fifteenth O site, O is bonded in a bent 150 degrees geometry to one U and one Cr atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on V2Cr2Fe by Materials Project

V2Cr2Fe crystallizes in the orthorhombic Fmm2 space group. The structure is three-dimensional. there are two inequivalent V sites. In the first V site, V is bonded in a 8-coordinate geometry to six V and two equivalent Cr atoms. There are four shorter (2.51 Å) and two longer (2.63 Å) V–V bond lengths. Both V–Cr bond lengths are 2.54 Å. In the second V site, V is bonded in a 8-coordinate geometry to two equivalent V and two equivalent Fe atoms. Both V–Fe bond lengths are 2.51 Å. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded in a 8-coordinate geometry to two equivalent Cr and two equivalent Fe atoms. Both Cr–Cr bond lengths are 2.45 Å. Both Cr–Fe bond lengths are 2.46 Å. In the second Cr site, Cr is bonded in a distorted body-centered cubic geometry to two equivalent V and six Cr atoms. All Cr–Cr bond lengths are 2.51 Å. Fe is bonded in a 8-coordinate geometry to two equivalent V and two equivalent Cr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2Cr2AsO10 by Materials Project

K2Cr2AsO10 crystallizes in the trigonal P3_1 space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded in a 7-coordinate geometry to eight O atoms. There are a spread of K–O bond distances ranging from 2.73–3.29 Å. In the second K site, K is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of K–O bond distances ranging from 2.73–3.23 Å. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share a cornercorner with one AsO4 tetrahedra. There are a spread of Cr–O bond distances ranging from 1.62–1.85 Å. In the second Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share a cornercorner with one AsO4 tetrahedra. There are a spread of Cr–O bond distances ranging from 1.62–1.86 Å. As is bonded to four O atoms to form AsO4 tetrahedra that share corners with two CrO4 tetrahedra. There is two shorter (1.70 Å) and two longer (1.76 Å) As–O bond length. There are ten inequivalent O sites. In the first O site, O is bonded in a distorted single-bond geometry to two K and one Cr atom. In the second O site, O is bonded in a distorted single-bond geometry to two K and one Cr atom. In the third O site, O is bonded in a distorted bent 120 degrees geometry to one K and one As atom. In the fourth O site, O is bonded in a distorted bent 120 degrees geometry to one K and one As atom. In the fifth O site, O is bonded in a distorted bent 120 degrees geometry to one K, one Cr, and one As atom. In the sixth O site, O is bonded in a distorted single-bond geometry to two K and one Cr atom. In the seventh O site, O is bonded in a distorted single-bond geometry to two K and one Cr atom. In the eighth O site, O is bonded in a distorted single-bond geometry to two K and one Cr atom. In the ninth O site, O is bonded in a distorted bent 120 degrees geometry to two K, one Cr, and one As atom. In the tenth O site, O is bonded in a distorted single-bond geometry to two K and one Cr atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr3O5 by Materials Project

Cr3O5 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are three inequivalent Cr+3.33+ sites. In the first Cr+3.33+ site, Cr+3.33+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing CrO5 trigonal bipyramids. There are a spread of Cr–O bond distances ranging from 1.79–2.05 Å. In the second Cr+3.33+ site, Cr+3.33+ is bonded to five O2- atoms to form a mixture of distorted edge, corner, and face-sharing CrO5 trigonal bipyramids. There are a spread of Cr–O bond distances ranging from 1.90–2.07 Å. In the third Cr+3.33+ site, Cr+3.33+ is bonded to five O2- atoms to form a mixture of distorted corner and face-sharing CrO5 trigonal bipyramids. There are a spread of Cr–O bond distances ranging from 1.94–2.03 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to three Cr+3.33+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to three Cr+3.33+ atoms. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to three Cr+3.33+ atoms. In the fourth O2- site, O2- is bonded in a T-shaped geometry to three Cr+3.33+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to three Cr+3.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2Cr4O19 by Materials Project

Cr4Al2O19 crystallizes in the monoclinic P2/c space group. The structure is two-dimensional and consists of one Cr4Al2O19 sheet oriented in the (0, 1, 0) direction. there are two inequivalent Cr sites. In the first Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share corners with three AlO6 octahedra. The corner-sharing octahedra tilt angles range from 30–43°. There are a spread of Cr–O bond distances ranging from 1.59–1.71 Å. In the second Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share a cornercorner with one AlO6 octahedra and a cornercorner with one CrO4 tetrahedra. The corner-sharing octahedral tilt angles are 15°. There are a spread of Cr–O bond distances ranging from 1.60–1.77 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with four equivalent CrO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.88–1.90 Å. In the second Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with four CrO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.86–1.91 Å. There are ten inequivalent O sites. In the first O site, O is bonded in a linear geometry to one Cr and one Al atom. In the second O site, O is bonded in a single-bond geometry to one Cr atom. In the third O site, O is bonded in a single-bond geometry to one Al atom. In the fourth O site, O is bonded in a bent 150 degrees geometry to one Cr and one Al atom. In the fifth O site, O is bonded in a single-bond geometry to one Al atom. In the sixth O site, O is bonded in a bent 150 degrees geometry to one Cr and one Al atom. In the seventh O site, O is bonded in a single-bond geometry to one Cr atom. In the eighth O site, O is bonded in a bent 150 degrees geometry to one Cr and one Al atom. In the ninth O site, O is bonded in a distorted bent 120 degrees geometry to two equivalent Cr atoms. In the tenth O site, O is bonded in a single-bond geometry to one Cr atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li32Mn11Cr5O48 by Materials Project

Li32Cr5Mn11O48 is beta Polonium-derived structured and crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are seventeen inequivalent Li sites. In the first Li site, Li is bonded to six O atoms to form LiO6 octahedra that share a cornercorner with one CrO6 octahedra, corners with two LiO6 octahedra, corners with three MnO6 octahedra, an edgeedge with one CrO6 octahedra, edges with three MnO6 octahedra, and edges with eight LiO6 octahedra. The corner-sharing octahedra tilt angles range from 5–10°. There are a spread of Li–O bond distances ranging from 2.06–2.21 Å. In the second Li site, Li is bonded to six O atoms to form LiO6 octahedra that share a cornercorner with one CrO6 octahedra, corners with two LiO6 octahedra, corners with three MnO6 octahedra, an edgeedge with one CrO6 octahedra, edges with three MnO6 octahedra, and edges with eight LiO6 octahedra. The corner-sharing octahedra tilt angles range from 5–9°. There are a spread of Li–O bond distances ranging from 2.04–2.21 Å. In the third Li site, Li is bonded to six O atoms to form LiO6 octahedra that share corners with six LiO6 octahedra, edges with three equivalent CrO6 octahedra, edges with three equivalent MnO6 octahedra, and edges with six LiO6 octahedra. The corner-sharing octahedra tilt angles range from 8–10°. There are a spread of Li–O bond distances ranging from 2.07–2.14 Å. In the fourth Li site, Li is bonded to six O atoms to form LiO6 octahedra that share a cornercorner with one CrO6 octahedra, corners with two LiO6 octahedra, corners with three MnO6 octahedra, an edgeedge with one CrO6 octahedra, edges with three MnO6 octahedra, and edges with eight LiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–8°. There are a spread of Li–O bond distances ranging from 2.03–2.20 Å. In the fifth Li site, Li is bonded to six O atoms to form LiO6 octahedra that share corners with six LiO6 octahedra, edges with three equivalent CrO6 octahedra, edges with three equivalent MnO6 octahedra, and edges with six LiO6 octahedra. The corner-sharing octahedra tilt angles range from 8–10°. There are a spread of Li–O bond distances ranging from 2.07–2.12 Å. In the sixth Li site, Li is bonded to six O atoms to form LiO6 octahedra that share a cornercorner with one CrO6 octahedra, corners with two LiO6 octahedra, corners with three MnO6 octahedra, an edgeedge with one CrO6 octahedra, edges with three MnO6 octahedra, and edges with eight LiO6 octahedra. The corner-sharing octahedra tilt angles range from 5–9°. There are a spread of Li–O bond distances ranging from 2.04–2.20 Å. In the seventh Li site, Li is bonded to six O atoms to form LiO6 octahedra that share corners with six LiO6 octahedra, edges with six LiO6 octahedra, and edges with six MnO6 octahedra. The corner-sharing octahedra tilt angles range from 8–9°. There are four shorter (2.09 Å) and two longer (2.11 Å) Li–O bond lengths. In the eighth Li site, Li is bonded to six O atoms to form LiO6 octahedra that share corners with two LiO6 octahedra, corners with two CrO6 octahedra, corners with two MnO6 octahedra, edges with two CrO6 octahedra, edges with two MnO6 octahedra, and edges with eight LiO6 octahedra. The corner-sharing octahedra tilt angles range from 6–9°. There are a spread of Li–O bond distances ranging from 2.05–2.21 Å. In the ninth Li site, Li is bonded to six O atoms to form LiO6 octahedra that share corners with two LiO6 octahedra, corners with two CrO6 octahedra, corners with two MnO6 octahedra, edges with two CrO6 octahedra, edges with two MnO6 octahedra, and edges with eight LiO6 octahedra. The corner-sharing octahedra tilt angles range from 5–9°. There are a spread of Li–O bond distances ranging from 2.03–2.20 Å. In the tenth Li site, Li is bonded to six O atoms to form LiO6 octahedra that share a cornercorner with one CrO6 octahedra, corners with two LiO6 octahedra, corners with three MnO6 octahedra, an edgeedge with one CrO6 octahedra, edges with three MnO6 octahedra, and edges with eight LiO6 octahedra. The corner-sharing octahedra tilt angles range from 8–9°. There are a spread of Li–O bond distances ranging from 2.06–2.21 Å. In the eleventh Li site, Li is bonded to six O atoms to form LiO6 octahedra that share corners with six LiO6 octahedra, edges with six LiO6 octahedra, and edges with six MnO6 octahedra. The corner-sharing octahedra tilt angles range from 8–9°. There are four shorter (2.09 Å) and two longer (2.11 Å) Li–O bond lengths. In the twelfth Li site, Li is bonded to six O atoms to form LiO6 octahedra that share a cornercorner with one CrO6 octahedra, corners with two LiO6 octahedra, corners with three MnO6 octahedra, an edgeedge with one CrO6 octahedra, edges with three MnO6 octahedra, and edges with eight LiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–10°. There are a spread of Li–O bond distances ranging from 2.07–2.22 Å. In the thirteenth Li site, Li is bonded to six O atoms to form LiO6 octahedra that share a cornercorner with one CrO6 octahedra, corners with two LiO6 octahedra, corners with three MnO6 octahedra, an edgeedge with one CrO6 octahedra, edges with three MnO6 octahedra, and edges with eight LiO6 octahedra. The corner-sharing octahedra tilt angles range from 8–9°. There are a spread of Li–O bond distances ranging from 2.06–2.22 Å. In the fourteenth Li site, Li is bonded to six O atoms to form LiO6 octahedra that share a cornercorner with one CrO6 octahedra, corners with two LiO6 octahedra, corners with three MnO6 octahedra, an edgeedge with one CrO6 octahedra, edges with three MnO6 octahedra, and edges with eight LiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–10°. There are a spread of Li–O bond distances ranging from 2.06–2.21 Å. In the fifteenth Li site, Li is bonded to six O atoms to form LiO6 octahedra that share a cornercorner with one CrO6 octahedra, corners with two LiO6 octahedra, corners with three MnO6 octahedra, an edgeedge with one CrO6 octahedra, edges with three MnO6 octahedra, and edges with eight LiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–10°. There are a spread of Li–O bond distances ranging from 2.07–2.21 Å. In the sixteenth Li site, Li is bonded to six O atoms to form LiO6 octahedra that share corners with two LiO6 octahedra, corners with two CrO6 octahedra, corners with two MnO6 octahedra, edges with two CrO6 octahedra, edges with two MnO6 octahedra, and edges with eight LiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–10°. There are a spread of Li–O bond distances ranging from 2.06–2.19 Å. In the seventeenth Li site, Li is bonded to six O atoms to form LiO6 octahedra that share corners with six LiO6 octahedra, edges with three equivalent CrO6 octahedra, edges with three equivalent MnO6 octahedra, and edges with six LiO6 octahedra. The corner-sharing octahedra tilt angles range from 8–10°. There are a spread of Li–O bond distances ranging from 2.07–2.12 Å. There are three inequivalent Cr sites. In the first Cr site, Cr is bonded to six O atoms to form CrO6 octahedra that share corners with six LiO6 octahedra, edges with three equivalent MnO6 octahedra, and edges with nine LiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–8°. There are a spread of Cr–O bond distances ranging from 1.90–1.98 Å. In the second Cr site, Cr is bonded to six O atoms to form CrO6 octahedra that share corners with six LiO6 octahedra, edges with three equivalent MnO6 octahedra, and edges with nine LiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–8°. There are a spread of Cr–O bond distances ranging from 1.91–1.99 Å. In the third Cr site, Cr is bonded to six O atoms to form CrO6 octahedra that share corners with six LiO6 octahedra, edges with three equivalent MnO6 octahedra, and edges with nine LiO6 octahedra. The corner-sharing octahedral tilt angles are 8°. There are a spread of Cr–O bond distances ranging from 1.90–1.98 Å. There are seven inequivalent Mn sites. In the first Mn site, Mn is bonded to six O atoms to form MnO6 octahedra that share corners with six LiO6 octahedra, edges with three equivalent MnO6 octahedra, and edges with nine LiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–8°. There is four shorter (1.94 Å) and two longer (1.95 Å) Mn–O bond length. In the second Mn site, Mn is bonded to six O atoms to form MnO6 octahedra that share corners with six LiO6 octahedra, edges with three equivalent MnO6 octahedra, and edges with nine LiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–8°. There is four shorter (1.94 Å) and two longer (1.95 Å) Mn–O bond length. In the third Mn site, Mn is bonded to six O atoms to form MnO6 octahedra that share corners with six LiO6 octahedra, edges with three equivalent CrO6 octahedra, and edges with nine LiO6 octahedra. The corner-sharing octahedra tilt angles range from 5–9°. There is two shorter (1.93 Å) and four longer (1.95 Å) Mn–O bond length. In the fourth Mn site, Mn is bonded to six O atoms to form MnO6 octahedra that share corners with six LiO6 octahedra, edges with three equivalent CrO6 octahedra, and edges with nine LiO6 octahedra. The corner-sharing octahedra tilt angles range from 5–9°. There are a spread of Mn–O bond distances ranging from 1.93–1.95 Å. In the fifth Mn site, Mn is bonded to six O atoms to form MnO6 octahedra that share corners with six LiO6 octahedra, edges with three equivalent CrO6 octahedra, and edges with nine LiO6 octahedra. The corner-sharing octahedra tilt angles range from 5–9°. There is two shorter (1.93 Å) and four longer (1.95 Å) Mn–O bond length. In the sixth Mn site, Mn is bonded to six O atoms to form MnO6 octahedra that share corners with six LiO6 octahedra, edges with three equivalent MnO6 octahedra, and edges with nine LiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–8°. There is two shorter (1.94 Å) and four longer (1.95 Å) Mn–O bond length. In the seventh Mn site, Mn is bonded to six O atoms to form MnO6 octahedra that share corners with six LiO6 octahedra, edges with three equivalent MnO6 octahedra, and edges with nine LiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–8°. There is two shorter (1.94 Å) and four longer (1.95 Å) Mn–O bond length. There are twenty-four inequivalent O sites. In the first O site, O is bonded to four Li, one Cr, and one Mn atom to form a mixture of edge and corner-sharing OLi4MnCr octahedra. The corner-sharing octahedra tilt angles range from 0–8°. In the second O site, O is bonded to four Li, one Cr, and one Mn atom to form a mixture of edge and corner-sharing OLi4MnCr octahedra. The corner-sharing octahedra tilt angles range from 1–8°. In the third O site, O is bonded to four Li and two Mn atoms to form a mixture of edge and corner-sharing OLi4Mn2 octahedra. The corner-sharing octahedra tilt angles range from 0–6°. In the fourth O site, O is bonded to four Li and two Mn atoms to form a mixture of edge and corner-sharing OLi4Mn2 octahedra. The corner-sharing octahedra tilt angles range from 0–8°. In the fifth O site, O is bonded to four Li, one Cr, and one Mn atom to form a mixture of edge and corner-sharing OLi4MnCr octahedra. The corner-sharing octahedra tilt angles range from 1–8°. In the sixth O site, O is bonded to four Li and two Mn atoms to form a mixture of edge and corner-sharing OLi4Mn2 octahedra. The corner-sharing octahedra tilt angles range from 0–6°. In the seventh O site, O is bonded to four Li and two Mn atoms to form a mixture of edge and corner-sharing OLi4Mn2 octahedra. The corner-sharing octahedra tilt angles range from 0–6°. In the eighth O site, O is bonded to four Li, one Cr, and one Mn atom to form a mixture of edge and corner-sharing OLi4MnCr octahedra. The corner-sharing octahedra tilt angles range from 0–8°. In the ninth O site, O is bonded to four Li, one Cr, and one Mn atom to form a mixture of edge a

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NdCrO5 by Materials Project

NdCrO5 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Nd sites. In the first Nd site, Nd is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Nd–O bond distances ranging from 2.36–2.64 Å. In the second Nd site, Nd is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Nd–O bond distances ranging from 2.39–2.57 Å. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded in a tetrahedral geometry to four O atoms. There are a spread of Cr–O bond distances ranging from 1.64–1.70 Å. In the second Cr site, Cr is bonded in a tetrahedral geometry to four O atoms. There is two shorter (1.65 Å) and two longer (1.69 Å) Cr–O bond length. There are ten inequivalent O sites. In the first O site, O is bonded in a 1-coordinate geometry to one Nd and one Cr atom. In the second O site, O is bonded in a distorted single-bond geometry to two Nd and one Cr atom. In the third O site, O is bonded in a distorted single-bond geometry to one Nd and one Cr atom. In the fourth O site, O is bonded in a distorted bent 150 degrees geometry to one Nd and one Cr atom. In the fifth O site, O is bonded in a distorted single-bond geometry to two Nd and one Cr atom. In the sixth O site, O is bonded in a trigonal non-coplanar geometry to three Nd atoms. In the seventh O site, O is bonded in a bent 150 degrees geometry to one Nd and one Cr atom. In the eighth O site, O is bonded in a distorted trigonal non-coplanar geometry to three Nd atoms. In the ninth O site, O is bonded in a bent 150 degrees geometry to one Nd and one Cr atom. In the tenth O site, O is bonded in a distorted bent 150 degrees geometry to one Nd and one Cr atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr4Fe2O19 by Materials Project

Cr4Fe2O19 crystallizes in the monoclinic P2/c space group. The structure is two-dimensional and consists of one Cr4Fe2O19 sheet oriented in the (0, 1, 0) direction. there are two inequivalent Cr sites. In the first Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share corners with three FeO6 octahedra. The corner-sharing octahedra tilt angles range from 33–43°. There are a spread of Cr–O bond distances ranging from 1.60–1.76 Å. In the second Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share a cornercorner with one FeO6 octahedra and a cornercorner with one CrO4 tetrahedra. The corner-sharing octahedral tilt angles are 13°. There are a spread of Cr–O bond distances ranging from 1.60–1.78 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with four equivalent CrO4 tetrahedra. There are a spread of Fe–O bond distances ranging from 1.83–2.10 Å. In the second Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with four CrO4 tetrahedra. There are a spread of Fe–O bond distances ranging from 1.96–2.10 Å. There are ten inequivalent O sites. In the first O site, O is bonded in a linear geometry to one Cr and one Fe atom. In the second O site, O is bonded in a single-bond geometry to one Cr atom. In the third O site, O is bonded in a single-bond geometry to one Fe atom. In the fourth O site, O is bonded in a bent 150 degrees geometry to one Cr and one Fe atom. In the fifth O site, O is bonded in a single-bond geometry to one Fe atom. In the sixth O site, O is bonded in a bent 150 degrees geometry to one Cr and one Fe atom. In the seventh O site, O is bonded in a single-bond geometry to one Cr atom. In the eighth O site, O is bonded in a bent 150 degrees geometry to one Cr and one Fe atom. In the ninth O site, O is bonded in a bent 120 degrees geometry to two equivalent Cr atoms. In the tenth O site, O is bonded in a single-bond geometry to one Cr atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr6C3N by Materials Project

Cr6C3N crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Cr+2.50+ sites. In the first Cr+2.50+ site, Cr+2.50+ is bonded to three C4- and one N3- atom to form corner-sharing CrC3N tetrahedra. All Cr–C bond lengths are 1.97 Å. The Cr–N bond length is 1.93 Å. In the second Cr+2.50+ site, Cr+2.50+ is bonded in a 5-coordinate geometry to five C4- atoms. There are a spread of Cr–C bond distances ranging from 1.98–2.36 Å. In the third Cr+2.50+ site, Cr+2.50+ is bonded in a 4-coordinate geometry to three equivalent C4- and two equivalent N3- atoms. There are two shorter (2.09 Å) and one longer (2.46 Å) Cr–C bond lengths. Both Cr–N bond lengths are 2.02 Å. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded to six Cr+2.50+ atoms to form CCr6 octahedra that share corners with two equivalent NCr6 octahedra and edges with two equivalent CCr6 octahedra. The corner-sharing octahedral tilt angles are 55°. In the second C4- site, C4- is bonded in a 8-coordinate geometry to eight Cr+2.50+ atoms. N3- is bonded to six Cr+2.50+ atoms to form NCr6 octahedra that share corners with two equivalent CCr6 octahedra and edges with two equivalent NCr6 octahedra. The corner-sharing octahedral tilt angles are 55°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U4Cr7Si by Materials Project

U4Cr7Si crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. there are two inequivalent U sites. In the first U site, U is bonded in a 12-coordinate geometry to four U and twelve Cr atoms. There are one shorter (2.98 Å) and three longer (3.13 Å) U–U bond lengths. There are a spread of U–Cr bond distances ranging from 2.94–3.01 Å. In the second U site, U is bonded in a 12-coordinate geometry to four U, nine equivalent Cr, and three equivalent Si atoms. All U–U bond lengths are 3.11 Å. There are six shorter (2.93 Å) and three longer (2.96 Å) U–Cr bond lengths. All U–Si bond lengths are 2.97 Å. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded to six U, five Cr, and one Si atom to form distorted CrU6Cr5Si cuboctahedra that share corners with two equivalent SiU6Cr6 cuboctahedra, corners with sixteen CrU6Cr5Si cuboctahedra, edges with six equivalent CrU6Cr5Si cuboctahedra, faces with three equivalent SiU6Cr6 cuboctahedra, and faces with fifteen CrU6Cr5Si cuboctahedra. There are a spread of Cr–Cr bond distances ranging from 2.48–2.56 Å. The Cr–Si bond length is 2.52 Å. In the second Cr site, Cr is bonded to six equivalent U and six equivalent Cr atoms to form CrU6Cr6 cuboctahedra that share corners with twelve equivalent CrU6Cr5Si cuboctahedra, edges with six equivalent CrU6Cr6 cuboctahedra, faces with two equivalent SiU6Cr6 cuboctahedra, and faces with eighteen equivalent CrU6Cr5Si cuboctahedra. Si is bonded to six equivalent U and six equivalent Cr atoms to form SiU6Cr6 cuboctahedra that share corners with twelve equivalent CrU6Cr5Si cuboctahedra, edges with six equivalent SiU6Cr6 cuboctahedra, and faces with twenty CrU6Cr6 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Development of Chromium and Sulfur Getter for Solid Oxide Fuel Cell (SOFC) System

Under the “real world” SOFC operating conditions, gaseous Cr and S species coexist in air stream. The combined Cr and S effect on the electrochemical poisoning of candidate LSM and LSCF electrodes has been investigated. Electrochemical and structural analysis revealed that the combined Cr and S interactions with the LSCF electrode remains significantly different from those of the individual Cr and S interactions. S reacts with the surface SrO accompanied by morphological changes whereas the hexavalent gaseous Cr species mainly deposit at the LSCF/GDC interface as is the case with Cr-only poisoning. For LSM electrode, the combined interactions of Cr and S remains similar to the sum of individual Cr and S effects as SO 2 reacts with Sr-rich regions of the bulk LSM, while Cr deposits at the electrochemically active sites. The use of getter, consisting of alkaline earth and transition metal oxides, has been proposed as a cost-effective approach to mitigate electrode poisoning. SrMnO 3 (SMO) is suggested as a robust getter material for the co-capture of airborne gaseous S and Cr species entering high-temperature electrochemical systems. The honeycomb getter forms, covered with SMO nanoparticles, were fabricated using dip coating. The SMO getter successfully maintained the electrochemical activity of LSM under the presence of gaseous Cr and S species, validating the efficacy of the getter. Post-test characterization revealed that the absorption of S and Cr contaminants led to the elongation of granular SMO particles, forming SrO nanorods and SrCrO 4 whiskers leaving Mn oxides underneath where inward-migrating Cr reside, indicating the high mutual affinity of Sr and Mn. The growth of reaction products during the long term exposure favors continued absorption of incoming S and Cr contaminants. The Mn 2 O 9 dimers, existing on the surface, are considered to help absorb S and Cr impurities, along with the Sr-terminated surface. The SMO getter also displays robust stability in humid environments at high temperatures without phase transformation or hydrolysis, fulfilling the requirement for operation in high-temperature electrochemical systems.

30 DIRECT ENERGY CONVERSION↗
NASA NTRSDate not supplied

Controlled Rest: Investigating the Use of an In-Flight Sleepiness Countermeasure

INTRODUCTION: Sleepiness is commonly reported amongst commercial airline pilots and is recognized as a safety risk due to its impact on performance. Controlled Rest (CR) refers to a short, voluntary nap opportunity taken by pilots on the flight deck as a countermeasure to unanticipated sleepiness in flight. This study explores the profile of CR use in a long-haul commercial airline. METHODS: Forty-four pilots filled in an application-based sleep/work diary and wore actiwatches for approximately 2 weeks. Complete data sets from 239 flights including sleep diaries, actigraphy, and schedules were merged and analyzed. Sleep diary entries were used to set CR intervals in the actigraphy software, which was then used to predict sleep within these intervals. All time-stamps of sleep periods and flight schedules were adjusted for home-base time of the pilots. Pearson Correlations were used to assess the influence of pilot demographics on CR use. A mixed-effects logistic regression was used to analyze the impact of schedule factors on CR. RESULTS: Pilots reported taking CR on 46% (n=110) of observed flights. Average CR attempt duration was 43.1 ± 11.0 minutes. Eighty-percent (n=106/133) of all CR attempts were estimated by actigraphy to have successfully achieved sleep with an average sleep duration during successful rest periods of 31.7 ± 12.2 minutes. Captains reported taking CR on 38% of flights (n=39/102), compared to First Officers reporting 52% (n=71/137) of flights with CR (p=0.131). Age, experience, BMI, and sleep need were not associated with the percentage of flights with CR (all p>0.244). The following schedule factors were associated with a higher frequency of CR: night (55%, n=76) vs. day flights (34%, n=34); <10h (63%, n=80) vs. >10h duration flights (27%, n=30); return (60%, n=71) vs. outbound flights (33%, n=39); and 2-pilot (69%, n=83) vs. >2-pilot flights (23%, n=27) (all p≤0.001). There was a trend for more CR on eastbound flights, but this was not significant (eastbound: 51%, n= 57; westbound: 40%, n= 44; p=0.059). Of note, 22% (n=26) of augmented flights (>2-pilots) contained both CR and Bunk Rest (in a designated rest facility). DISCUSSION: Data from this airline show that pilots commonly use CR to mitigate sleepiness in-flight, especially on flights <10h duration and during home-base nighttime flights. Future studies are required to determine generalizability of these results to other airlines.

sleepiness↗
DOE OSTI2020

Chemical-Biological Cyclic Process for Hexavalent Chromium Reduction to Trivalent Chromium in Aqueous Medium - 20224

Conventional treatment of chromium contamination focuses on immobilization of the highly toxic and water-soluble form Cr(VI), by reducing it to the relatively less toxic and less mobile trivalent form, Cr(III), using reducing compounds like ferrous sulfate or ferrous iron, Fe(II). The Cr(VI) also respond to biodegradation and subsequent reduction. During the reduction reaction, Fe(II) is oxidized to ferric, Fe(III), which, being at the highest oxidation state, has no ability to reduce Cr(VI), and therefore remediation process terminates. The good news is that metal-reducing bacteria, S. oneidensis MR-1, can regenerate Fe(II) from Fe(III) with the help of an organic electron donor in an appropriate bacterial media. Thus, in the Cr(VI) chemical remediation process, Fe(II) to Fe(III) conversion is reversed by the biological process, regenerating Fe(II) and the Cr(VI) chemical reduction process continues in a cyclic fashion. This study presents the results of regeneration of Fe(II) from fresh Fe(III) as well as from the reaction products of Cr(VI) and Fe(II). Both fresh Fe(III) and reaction product Fe(III) exhibited the same reduction behavior. Fe(II) production increased with the increase of initial concentration of Fe(III), resulting in 87.5% Fe(II) regeneration. The extent of Fe(III) reduction (Fe(II)t/Fe(III)0.hour) was 21 times higher than the extent of Cr(VI) reduction (Cr(VI)t/Cr(VI)0.hour) by S. oneidensis MR-1. In a cyclic process of sequential Cr(VI) addition, the amount of Fe(II) regeneration decreased with the increase in cycle number, a fixed quantity of starting S. oneidensis MR-1 could regenerate Fe(II) at least five times in a ten-hour period. More importantly, regenerated Fe(II) instantly reduced Cr(VI) to Cr(III). So, Fe(II) regeneration with metal-reducing bacteria has a good potential for application in groundwater and wastewater remediation in reducing Cr(VI) to Cr(III). As a comparison of chemical to biological transformation, chemical transformation of Cr(VI) by Fe(II) was almost 600 times greater than that of biological transformation. Therefore a chemical-biological cyclic process offers potential applications for remediation of groundwater and hexavalent chromium contaminated waste sites. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗