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99 GENERAL AND MISCELLANEOUS↗
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99 GENERAL AND MISCELLANEOUS↗
Materials Data on K8Al2O7 by Materials Project
K8Al2O7 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are eight inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to four O2- atoms to form KO4 tetrahedra that share a cornercorner with one KO4 tetrahedra, corners with four AlO4 tetrahedra, and edges with two KO4 tetrahedra. There are a spread of K–O bond distances ranging from 2.62–2.74 Å. In the second K1+ site, K1+ is bonded in a 2-coordinate geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.59–3.25 Å. In the third K1+ site, K1+ is bonded in a distorted hexagonal planar geometry to six O2- atoms. There are a spread of K–O bond distances ranging from 2.80–2.87 Å. In the fourth K1+ site, K1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.55–3.05 Å. In the fifth K1+ site, K1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.65–3.08 Å. In the sixth K1+ site, K1+ is bonded to four O2- atoms to form distorted KO4 tetrahedra that share a cornercorner with one KO4 tetrahedra, corners with two AlO4 tetrahedra, an edgeedge with one AlO4 tetrahedra, and edges with two KO4 tetrahedra. There are a spread of K–O bond distances ranging from 2.53–2.75 Å. In the seventh K1+ site, K1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.61–3.17 Å. In the eighth K1+ site, K1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.59–2.75 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with four KO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.80–1.88 Å. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra, corners with two KO4 tetrahedra, and an edgeedge with one KO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.82–1.87 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to five K1+ and one Al3+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to four K1+ and two Al3+ atoms. In the third O2- site, O2- is bonded in a 6-coordinate geometry to five K1+ and one Al3+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to six K1+ and one Al3+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to five K1+ and one Al3+ atom. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to five K1+ and one Al3+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to six K1+ and one Al3+ atom.
36 MATERIALS SCIENCE↗
Materials Data on KSeNO2 by Materials Project
KNSeO2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are three inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of K–O bond distances ranging from 2.75–3.17 Å. In the second K1+ site, K1+ is bonded to six O2- atoms to form distorted KO6 pentagonal pyramids that share corners with six SeN2O2 tetrahedra and edges with three equivalent KO6 octahedra. There are a spread of K–O bond distances ranging from 2.82–2.97 Å. In the third K1+ site, K1+ is bonded to six O2- atoms to form distorted KO6 octahedra that share corners with six SeN2O2 tetrahedra, an edgeedge with one KO6 octahedra, and edges with three equivalent KO6 pentagonal pyramids. There are a spread of K–O bond distances ranging from 2.71–2.96 Å. There are three inequivalent N5+ sites. In the first N5+ site, N5+ is bonded in a water-like geometry to two Se2- atoms. Both N–Se bond lengths are 1.81 Å. In the second N5+ site, N5+ is bonded in a water-like geometry to two Se2- atoms. There is one shorter (1.81 Å) and one longer (1.82 Å) N–Se bond length. In the third N5+ site, N5+ is bonded in a bent 120 degrees geometry to two Se2- atoms. There is one shorter (1.80 Å) and one longer (1.82 Å) N–Se bond length. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two N5+ and two O2- atoms to form SeN2O2 tetrahedra that share a cornercorner with one KO6 octahedra, corners with two equivalent KO6 pentagonal pyramids, and corners with two SeN2O2 tetrahedra. The corner-sharing octahedral tilt angles are 64°. There is one shorter (1.66 Å) and one longer (1.67 Å) Se–O bond length. In the second Se2- site, Se2- is bonded to two N5+ and two O2- atoms to form SeN2O2 tetrahedra that share corners with three equivalent KO6 octahedra, corners with two equivalent KO6 pentagonal pyramids, and corners with two SeN2O2 tetrahedra. The corner-sharing octahedra tilt angles range from 63–75°. There is one shorter (1.65 Å) and one longer (1.67 Å) Se–O bond length. In the third Se2- site, Se2- is bonded to two N5+ and two O2- atoms to form SeN2O2 tetrahedra that share corners with two equivalent KO6 octahedra, corners with two equivalent KO6 pentagonal pyramids, and corners with two SeN2O2 tetrahedra. The corner-sharing octahedra tilt angles range from 57–61°. There is one shorter (1.66 Å) and one longer (1.67 Å) Se–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to three K1+ and one Se2- atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three K1+ and one Se2- atom. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three K1+ and one Se2- atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to three K1+ and one Se2- atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to three K1+ and one Se2- atom. In the sixth O2- site, O2- is bonded in a distorted tetrahedral geometry to three K1+ and one Se2- atom.
36 MATERIALS SCIENCE↗
Materials Data on K4SnO4 by Materials Project
K4SnO4 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.72–2.81 Å. In the second K1+ site, K1+ is bonded to five O2- atoms to form distorted KO5 trigonal bipyramids that share corners with three equivalent KO5 square pyramids, corners with two equivalent KO4 tetrahedra, corners with three equivalent SnO4 tetrahedra, edges with three equivalent KO5 square pyramids, an edgeedge with one SnO4 tetrahedra, and edges with two equivalent KO5 trigonal bipyramids. There are a spread of K–O bond distances ranging from 2.68–2.88 Å. In the third K1+ site, K1+ is bonded to four O2- atoms to form distorted KO4 tetrahedra that share corners with two equivalent KO5 square pyramids, corners with four equivalent SnO4 tetrahedra, corners with two equivalent KO5 trigonal bipyramids, and edges with two equivalent KO4 tetrahedra. There are a spread of K–O bond distances ranging from 2.66–2.71 Å. In the fourth K1+ site, K1+ is bonded to five O2- atoms to form distorted KO5 square pyramids that share a cornercorner with one SnO4 tetrahedra, corners with two equivalent KO4 tetrahedra, corners with three equivalent KO5 trigonal bipyramids, edges with two equivalent KO5 square pyramids, edges with two equivalent SnO4 tetrahedra, and edges with three equivalent KO5 trigonal bipyramids. There are a spread of K–O bond distances ranging from 2.76–2.93 Å. Sn4+ is bonded to four O2- atoms to form SnO4 tetrahedra that share a cornercorner with one KO5 square pyramid, corners with four equivalent KO4 tetrahedra, corners with three equivalent KO5 trigonal bipyramids, edges with two equivalent KO5 square pyramids, and an edgeedge with one KO5 trigonal bipyramid. There are one shorter (1.99 Å) and three longer (2.01 Å) Sn–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to five K1+ and one Sn4+ atom to form a mixture of edge and corner-sharing OK5Sn octahedra. The corner-sharing octahedra tilt angles range from 10–30°. In the second O2- site, O2- is bonded to five K1+ and one Sn4+ atom to form a mixture of distorted edge and corner-sharing OK5Sn octahedra. The corner-sharing octahedra tilt angles range from 10–30°. In the third O2- site, O2- is bonded to five K1+ and one Sn4+ atom to form a mixture of distorted edge and corner-sharing OK5Sn octahedra. The corner-sharing octahedra tilt angles range from 17–19°. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to three K1+ and one Sn4+ atom.
36 MATERIALS SCIENCE↗
Energetics of Ag Adsorption on and Adhesion to Rutile TiO 2 (100) Studied by Microcalorimetry
The adsorption and adhesion energies of vapor-deposited Ag on rutile TiO 2 (100) films have been measured using single crystal adsorption calorimetry (SCAC) and He + low energy ion scattering spectroscopy (LEIS). Ag grows as three-dimensional (3D) nanoparticles at 300 and 100 K. The saturation particle density is 8 × 10 16 particles/m 2 at 300 K and 2.5 × 10 17 particles/m 2 at 100 K. The differential heat of adsorption starts low, increases with Ag coverage, and finally approaches the sublimation enthalpy of Ag at both 300 and 100 K. At 300 K, the differential heat of adsorption starts from 208 kJ/mol and rises rapidly to 265 kJ/mol by 1 ML. At 100 K, Ag grows nanoparticles with smaller particle size on the terraces, while at 300 K, the Ag nanoparticles have bigger particle size and grow on step edges with stronger binding strength to the nanoparticles. Thus, the heat of Ag adsorption at 100 K starts at 141 kJ/mol (near the monomer size limit on terrace sites) and remains lower than that at 300 K until 1.5 ML. Here, the adhesion energy of Ag(solid) to rutile TiO 2 (100) is found to be large (~2.44 J/m 2 ), supporting a trend of decreasing adhesion energy with the enthalpy of oxide reduction.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Materials Data on K9Ce(PS4)4 by Materials Project
K9Ce(PS4)4 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are five inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of K–S bond distances ranging from 3.33–3.78 Å. In the second K1+ site, K1+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of K–S bond distances ranging from 3.20–3.88 Å. In the third K1+ site, K1+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of K–S bond distances ranging from 3.19–3.52 Å. In the fourth K1+ site, K1+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of K–S bond distances ranging from 3.19–3.53 Å. In the fifth K1+ site, K1+ is bonded to eight S2- atoms to form distorted KS8 hexagonal bipyramids that share edges with two equivalent CeS8 hexagonal bipyramids and edges with four PS4 tetrahedra. There are a spread of K–S bond distances ranging from 3.26–3.36 Å. Ce3+ is bonded to eight S2- atoms to form distorted CeS8 hexagonal bipyramids that share edges with two equivalent KS8 hexagonal bipyramids and edges with four PS4 tetrahedra. There are a spread of Ce–S bond distances ranging from 2.99–3.05 Å. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four S2- atoms to form PS4 tetrahedra that share an edgeedge with one KS8 hexagonal bipyramid and an edgeedge with one CeS8 hexagonal bipyramid. There are a spread of P–S bond distances ranging from 2.04–2.08 Å. In the second P5+ site, P5+ is bonded to four S2- atoms to form PS4 tetrahedra that share an edgeedge with one KS8 hexagonal bipyramid and an edgeedge with one CeS8 hexagonal bipyramid. There are a spread of P–S bond distances ranging from 2.04–2.08 Å. There are eight inequivalent S2- sites. In the first S2- site, S2- is bonded in a 6-coordinate geometry to four K1+, one Ce3+, and one P5+ atom. In the second S2- site, S2- is bonded in a 1-coordinate geometry to four K1+, one Ce3+, and one P5+ atom. In the third S2- site, S2- is bonded in a 1-coordinate geometry to three K1+, one Ce3+, and one P5+ atom. In the fourth S2- site, S2- is bonded in a 1-coordinate geometry to five K1+ and one P5+ atom. In the fifth S2- site, S2- is bonded in a 1-coordinate geometry to five K1+ and one P5+ atom. In the sixth S2- site, S2- is bonded in a 1-coordinate geometry to four K1+, one Ce3+, and one P5+ atom. In the seventh S2- site, S2- is bonded in a 1-coordinate geometry to five K1+ and one P5+ atom. In the eighth S2- site, S2- is bonded in a 1-coordinate geometry to five K1+ and one P5+ atom.
36 MATERIALS SCIENCE↗
Materials Data on K9Nd(PS4)4 by Materials Project
K9Nd(PS4)4 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are five inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of K–S bond distances ranging from 3.18–3.52 Å. In the second K1+ site, K1+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of K–S bond distances ranging from 3.18–3.52 Å. In the third K1+ site, K1+ is bonded to eight S2- atoms to form distorted KS8 hexagonal bipyramids that share edges with two equivalent NdS8 hexagonal bipyramids and edges with four PS4 tetrahedra. There are a spread of K–S bond distances ranging from 3.24–3.31 Å. In the fourth K1+ site, K1+ is bonded in a 8-coordinate geometry to seven S2- atoms. There are a spread of K–S bond distances ranging from 3.23–3.71 Å. In the fifth K1+ site, K1+ is bonded in a 4-coordinate geometry to seven S2- atoms. There are a spread of K–S bond distances ranging from 3.36–3.76 Å. Nd3+ is bonded to eight S2- atoms to form distorted NdS8 hexagonal bipyramids that share edges with two equivalent KS8 hexagonal bipyramids and edges with four PS4 tetrahedra. There are four shorter (3.00 Å) and four longer (3.02 Å) Nd–S bond lengths. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four S2- atoms to form PS4 tetrahedra that share an edgeedge with one KS8 hexagonal bipyramid and an edgeedge with one NdS8 hexagonal bipyramid. There are two shorter (2.04 Å) and two longer (2.07 Å) P–S bond lengths. In the second P5+ site, P5+ is bonded to four S2- atoms to form PS4 tetrahedra that share an edgeedge with one KS8 hexagonal bipyramid and an edgeedge with one NdS8 hexagonal bipyramid. There are a spread of P–S bond distances ranging from 2.03–2.07 Å. There are eight inequivalent S2- sites. In the first S2- site, S2- is bonded in a 1-coordinate geometry to five K1+ and one P5+ atom. In the second S2- site, S2- is bonded in a 1-coordinate geometry to three K1+, one Nd3+, and one P5+ atom. In the third S2- site, S2- is bonded in a 1-coordinate geometry to five K1+ and one P5+ atom. In the fourth S2- site, S2- is bonded in a 1-coordinate geometry to five K1+ and one P5+ atom. In the fifth S2- site, S2- is bonded in a 1-coordinate geometry to three K1+, one Nd3+, and one P5+ atom. In the sixth S2- site, S2- is bonded in a 1-coordinate geometry to five K1+ and one P5+ atom. In the seventh S2- site, S2- is bonded in a 1-coordinate geometry to four K1+, one Nd3+, and one P5+ atom. In the eighth S2- site, S2- is bonded in a 1-coordinate geometry to four K1+, one Nd3+, and one P5+ atom.
36 MATERIALS SCIENCE↗
Materials Data on K2O by Materials Project
K2O crystallizes in the trigonal P3 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.83–3.06 Å. In the second K1+ site, K1+ is bonded to four O2- atoms to form a mixture of distorted corner and edge-sharing KO4 tetrahedra. There are a spread of K–O bond distances ranging from 2.63–2.89 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 6-coordinate geometry to six K1+ atoms. In the second O2- site, O2- is bonded in a 9-coordinate geometry to nine K1+ atoms. In the third O2- site, O2- is bonded in a 9-coordinate geometry to nine K1+ atoms.
36 MATERIALS SCIENCE↗
Materials Data on KAu2 by Materials Project
KAu2 is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. K is bonded in a 12-coordinate geometry to twelve Au atoms. There are a spread of K–Au bond distances ranging from 3.38–3.52 Å. There are two inequivalent Au sites. In the first Au site, Au is bonded to six equivalent K and six equivalent Au atoms to form a mixture of distorted corner, edge, and face-sharing AuK6Au6 cuboctahedra. All Au–Au bond lengths are 3.00 Å. In the second Au site, Au is bonded to six equivalent K and six Au atoms to form a mixture of corner, edge, and face-sharing AuK6Au6 cuboctahedra. There are two shorter (2.88 Å) and two longer (2.89 Å) Au–Au bond lengths.
36 MATERIALS SCIENCE↗
Formation of a Ti–Cu(111) single atom alloy: Structure and CO binding
A single atom Ti–Cu(111) surface alloy can be generated by depositing small amounts of Ti onto Cu(111) at slightly elevated surface temperatures (~500 to 600 K). Here, scanning tunneling microscopy shows that small Ti-rich islands covered by a Cu single layer form preferentially on ascending step edges of Cu(111) during Ti deposition below about 400 K but that a Ti–Cu(111) alloy replaces these small islands during deposition between 500 and 600 K, producing an alloy in the brims of the steps. Larger partially Cu-covered Ti-containing islands also form on the Cu(111) terraces at temperatures between 300 and 700 K. After surface exposure to CO at low temperatures, reflection absorption infrared spectroscopy (RAIRS) reveals distinct C–O stretch bands at 2102 and 2050 cm –1 attributed to CO adsorbed on Cu-covered Ti-containing domains vs sites in the Ti–Cu(111) surface alloy. Calculations using density functional theory (DFT) suggest that the lower frequency C–O stretch band originates specifically from CO adsorbed on isolated Ti atoms in the Ti–Cu(111) surface alloy and predicts a higher C–O stretch frequency for CO adsorbed on Cu above subsurface Ti ensembles. DFT further predicts that CO preferentially adsorbs in flat-lying configurations on contiguous Ti surface structures with more than one Ti atom and thus that CO adsorbed on such structures should not be observed with RAIRS. The ability to generate a single atom Ti–Cu(111) alloy will provide future opportunities to investigate the surface chemistry promoted by a representative early transition metal dopant on a Cu(111) host surface.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Materials Data on K2Ta3Cl9 by Materials Project
K2Ta3Cl9 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. K is bonded in a 6-coordinate geometry to six Cl atoms. There are a spread of K–Cl bond distances ranging from 3.09–3.67 Å. There are two inequivalent Ta sites. In the first Ta site, Ta is bonded to five Cl atoms to form distorted corner-sharing TaCl5 square pyramids. There are a spread of Ta–Cl bond distances ranging from 2.47–2.59 Å. In the second Ta site, Ta is bonded to five Cl atoms to form distorted corner-sharing TaCl5 square pyramids. There are a spread of Ta–Cl bond distances ranging from 2.47–2.64 Å. There are six inequivalent Cl sites. In the first Cl site, Cl is bonded in a 2-coordinate geometry to two equivalent K and two equivalent Ta atoms. In the second Cl site, Cl is bonded to three equivalent K and one Ta atom to form a mixture of edge and corner-sharing ClK3Ta tetrahedra. In the third Cl site, Cl is bonded in a trigonal planar geometry to two equivalent K and one Ta atom. In the fourth Cl site, Cl is bonded in a 3-coordinate geometry to one K and two Ta atoms. In the fifth Cl site, Cl is bonded in a 2-coordinate geometry to two equivalent Ta atoms. In the sixth Cl site, Cl is bonded in a 2-coordinate geometry to two Ta atoms.
36 MATERIALS SCIENCE↗
Materials Data on K2IO9 by Materials Project
K2O9I crystallizes in the triclinic P-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 seven O atoms. There are a spread of K–O bond distances ranging from 2.76–3.10 Å. In the second K site, K is bonded in a 7-coordinate geometry to seven O atoms. There are a spread of K–O bond distances ranging from 2.72–3.05 Å. There are nine inequivalent O sites. In the first O site, O is bonded in a distorted trigonal planar geometry to two equivalent K and one I atom. The O–I bond length is 1.80 Å. In the second O site, O is bonded in a 3-coordinate geometry to two equivalent K and one I atom. The O–I bond length is 1.80 Å. In the third O site, O is bonded in a linear geometry to one K and one I atom. The O–I bond length is 1.80 Å. In the fourth O site, O is bonded in a distorted bent 150 degrees geometry to one K and one I atom. The O–I bond length is 1.80 Å. In the fifth O site, O is bonded in a bent 120 degrees geometry to one K and one O atom. The O–O bond length is 1.33 Å. In the sixth O site, O is bonded to three K and one O atom to form distorted edge-sharing OK3O tetrahedra. The O–O bond length is 1.40 Å. In the seventh O site, O is bonded in a distorted trigonal non-coplanar geometry to two equivalent K and one O atom. The O–O bond length is 1.23 Å. In the eighth O site, O is bonded in a bent 120 degrees geometry to one K and one O atom. In the ninth O site, O is bonded in a 3-coordinate geometry to one K and two O atoms. I is bonded in a tetrahedral geometry to four O atoms.
36 MATERIALS SCIENCE↗
Materials Data on K6BiH3(Cl2F)4 by Materials Project
K6BiH3(Cl2F)4 crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six Cl1- atoms to form KCl6 octahedra that share edges with two equivalent BiCl6 octahedra and edges with four equivalent KCl6 octahedra. There are a spread of K–Cl bond distances ranging from 3.08–3.36 Å. In the second K1+ site, K1+ is bonded in a 2-coordinate geometry to six Cl1- and two equivalent F1- atoms. There are a spread of K–Cl bond distances ranging from 3.25–3.37 Å. Both K–F bond lengths are 2.73 Å. Bi3+ is bonded to six Cl1- atoms to form BiCl6 octahedra that share edges with six equivalent KCl6 octahedra. There are three shorter (2.73 Å) and three longer (2.75 Å) Bi–Cl bond lengths. H1+ is bonded in a linear geometry to two F1- atoms. There is one shorter (1.01 Å) and one longer (1.40 Å) H–F bond length. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded to six K1+ atoms to form distorted ClK6 octahedra that share corners with three equivalent ClK6 octahedra, corners with six equivalent ClK4Bi square pyramids, edges with nine ClK4Bi square pyramids, and a faceface with one ClK6 octahedra. The corner-sharing octahedral tilt angles are 3°. In the second Cl1- site, Cl1- is bonded to six K1+ atoms to form ClK6 octahedra that share corners with three equivalent ClK6 octahedra, corners with six equivalent ClK4Bi square pyramids, edges with nine ClK4Bi square pyramids, and a faceface with one ClK6 octahedra. The corner-sharing octahedral tilt angles are 3°. In the third Cl1- site, Cl1- is bonded to four K1+ and one Bi3+ atom to form distorted ClK4Bi square pyramids that share corners with two equivalent ClK6 octahedra, corners with seven ClK4Bi square pyramids, edges with three ClK6 octahedra, and edges with five ClK4Bi square pyramids. The corner-sharing octahedral tilt angles are 37°. In the fourth Cl1- site, Cl1- is bonded to four K1+ and one Bi3+ atom to form distorted ClK4Bi square pyramids that share corners with two equivalent ClK6 octahedra, corners with seven ClK4Bi square pyramids, edges with three ClK6 octahedra, and edges with five ClK4Bi square pyramids. The corner-sharing octahedral tilt angles are 37°. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a trigonal planar geometry to three equivalent H1+ atoms. In the second F1- site, F1- is bonded in a distorted single-bond geometry to two equivalent K1+ and one H1+ atom.
36 MATERIALS SCIENCE↗
Materials Data on K4CrO4 by Materials Project
K4CrO4 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.70–2.89 Å. In the second K1+ site, K1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.70–3.07 Å. In the third K1+ site, K1+ is bonded to four O2- atoms to form distorted KO4 tetrahedra that share corners with four equivalent CrO4 tetrahedra, corners with two equivalent KO5 trigonal bipyramids, and edges with two equivalent KO4 tetrahedra. There are a spread of K–O bond distances ranging from 2.64–2.71 Å. In the fourth K1+ site, K1+ is bonded to five O2- atoms to form distorted KO5 trigonal bipyramids that share corners with two equivalent KO4 tetrahedra, corners with three equivalent CrO4 tetrahedra, an edgeedge with one CrO4 tetrahedra, and edges with two equivalent KO5 trigonal bipyramids. There are a spread of K–O bond distances ranging from 2.66–2.85 Å. Cr4+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with four equivalent KO4 tetrahedra, corners with three equivalent KO5 trigonal bipyramids, and an edgeedge with one KO5 trigonal bipyramid. There are a spread of Cr–O bond distances ranging from 1.81–1.84 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to five K1+ and one Cr4+ atom to form distorted edge-sharing OK5Cr octahedra. In the second O2- site, O2- is bonded in a 1-coordinate geometry to five K1+ and one Cr4+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to five K1+ and one Cr4+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to four K1+ and one Cr4+ atom.
36 MATERIALS SCIENCE↗
Spectral function of the $J_1$ – $J_2$ Heisenberg model on the triangular lattice
Spectral probes, such as neutron scattering, are crucial for characterizing excitations in quantum many-body systems and the properties of quantum materials. Among the most elusive phases of matter are quantum spin liquids, which have no long-range order even at zero temperature and host exotic fractionalized excitations with nontrivial statistics. These phases can occur in frustrated quantum magnets, such as the paradigmatic Heisenberg model with nearest- and next-nearest-neighbor exchange interactions on the triangular lattice, the so-called $J_1$ – $J_2$ model. In this work, we compute the spectral function using large-scale matrix product state simulations across the three different phases of this model's phase diagram, including a quantum spin-liquid phase at intermediate $J_2$/$J_1$. Despite a plethora of theoretical and experimental studies, the exact nature of this phase is still contested, with the dominant candidates being a gapped $\mathbb{Z}_2$, a gapless U(1) Dirac, and a spinon Fermi surface quantum spin-liquid state. We find a V-shaped spectrum near the center of the Brillouin zone ($Γ$ point), a key signature of a spinon Fermi surface, observed in prior neutron scattering experiments. However, we find a small gap near the $Γ$ point, ruling out such a phase. Furthermore, we find localized gapless excitations at the corner of the Brillouin zone boundary (K point) and the middle of the edge of the Brillouin zone boundary (M point), ruling out the gapped $\mathbb{Z}_2$ spin-liquid phase. Here, our results imply that the intermediate spin-liquid phase is a gapless $U(1)$ Dirac spin liquid, and provide clear signatures to detect this phase in future neutron scattering experiments.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Materials Data on KBe2BO3F2 by Materials Project
KBe2BO3F2 crystallizes in the trigonal R-3c space group. The structure is three-dimensional. K1+ is bonded to six equivalent F1- atoms to form distorted KF6 octahedra that share corners with six equivalent BeO3F tetrahedra and edges with six equivalent KF6 octahedra. All K–F bond lengths are 2.81 Å. Be2+ is bonded to three equivalent O2- and one F1- atom to form BeO3F tetrahedra that share corners with three equivalent KF6 octahedra and corners with three equivalent BeO3F tetrahedra. The corner-sharing octahedral tilt angles are 66°. All Be–O bond lengths are 1.64 Å. The Be–F bond length is 1.55 Å. B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.38 Å. O2- is bonded in a trigonal planar geometry to two equivalent Be2+ and one B3+ atom. F1- is bonded in a distorted single-bond geometry to three equivalent K1+ and one Be2+ atom.
36 MATERIALS SCIENCE↗
Trip-Induced Transition Measurements in a Hypersonic Boundary Layer Using Molecular Tagging Velocimetry
Measurements of mean streamwise velocity, fluctuating streamwise velocity, and instantaneous streamwise velocity profiles in a hypersonic boundary layer were obtained over a 10-degree half-angle wedge model. A laser-induced fluorescence-based molecular tagging velocimetry technique was used to make the measurements. The nominal edge Mach number was 4.2. Velocity profiles were measured both in an untripped boundary layer and in the wake of a 4-mm diameter cylindrical tripping element centered 75.4 mm downstream of the sharp leading edge. Three different trip heights were investigated: k = 0.53 mm, k = 1.0 mm and k = 2.0 mm. The laminar boundary layer thickness at the position of the measurements was approximately 1 mm, though the exact thickness was dependent on Reynolds number and wall temperature. All of the measurements were made starting from a streamwise location approximately 18 mm downstream of the tripping element. This measurement region continued approximately 30 mm in the streamwise direction. Additionally, measurements were made at several spanwise locations. An analysis of flow features show how the magnitude, spatial location, and spatial growth of streamwise velocity instabilities are affected by parameters such as the ratio of trip height to boundary layer thickness and roughness Reynolds number. The fluctuating component of streamwise velocity measured along the centerline of the model increased from approximately 75 m/s with no trip to +/-225 m/s with a 0.53-mm trip, and to +/-240 m/s with a 1-mm trip, while holding the freestream Reynolds number constant. These measurements were performed in the 31-inch Mach 10 Air Tunnel at the NASA Langley Research Center.
Bathel, Brett F.↗