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11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

KCo 2 As 2 : A new portal for the physics of high-purity metals

High-quality single crystals of KCo 2 As 2 with the body-centered tetragonal ThCr 2 Si 2 structure were grown using KAs self flux. Structural, magnetic, thermal, and electrical transport properties were investigated. No clear evidence for any phase transitions was found in the temperature range 2–300 K. The in-plane electrical resistivity ρ versus temperature T is highly unusual, showing a T 4 behavior below 30 K and an anomalous positive curvature up to 300 K, which is different from the linear behavior expected from the Bloch-Grüneisen theory for electron scattering by acoustic phonons. This positive curvature has been previously observed in the in-plane resistivity of high-conductivity layered delafossites such as PdCoO 2 and PtCoO 2 . The in-plane ρ(T → 0) = 0.36μΩ cm of KCo 2 As 2 is exceptionally small for this class of compounds. The material also exhibits a magnetoresistance at low T which attains a value of about 40% at T = 2 K and magnetic field H = 80 kOe. The magnetic susceptibility χ of KCo 2 As 2 is isotropic and about an order of magnitude smaller than the values for the related compounds SrCo 2 As 2 and BaCo 2 As 2 . The χ increases above 100 K, which is found from our first-principles calculations to arise from a sharp peak in the electronic density of states just above the Fermi energy E F . Heat capacity C p (T) data at low T yield an electronic density of states N(E F ) that is about 36% larger than predicted by the first-principles theory. The C p (T) data near room temperature suggest the presence of excited optic vibration modes, which may also be the source of the positive curvature in ρ(T). Angle-resolved photoemission spectroscopy measurements are compared with the theoretical predictions of the band structure and Fermi surfaces. In conclusion, our results show that KCo 2 As 2 provides a new avenue for investigating the physics of high-purity metals.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KCo(CO)4 by Materials Project

KCo(CO)4 crystallizes in the triclinic P1 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 2.76–3.26 Å. In the second K1+ site, K1+ is bonded in a distorted pentagonal planar geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.75–3.14 Å. In the third K1+ site, K1+ is bonded in a distorted pentagonal planar geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.74–3.21 Å. In the fourth K1+ site, K1+ is bonded in a distorted pentagonal planar geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.74–3.25 Å. There are four inequivalent Co1+ sites. In the first Co1+ site, Co1+ is bonded in a tetrahedral geometry to four C+1.50+ atoms. There are a spread of Co–C bond distances ranging from 1.73–1.75 Å. In the second Co1+ site, Co1+ is bonded in a tetrahedral geometry to four C+1.50+ atoms. There is three shorter (1.74 Å) and one longer (1.75 Å) Co–C bond length. In the third Co1+ site, Co1+ is bonded in a tetrahedral geometry to four C+1.50+ atoms. There is three shorter (1.74 Å) and one longer (1.75 Å) Co–C bond length. In the fourth Co1+ site, Co1+ is bonded in a tetrahedral geometry to four C+1.50+ atoms. There is three shorter (1.74 Å) and one longer (1.75 Å) Co–C bond length. There are sixteen inequivalent C+1.50+ sites. In the first C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.18 Å. In the second C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.17 Å. In the third C+1.50+ site, C+1.50+ is bonded in a distorted linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.17 Å. In the fourth C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.17 Å. In the fifth C+1.50+ site, C+1.50+ is bonded in a distorted linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.18 Å. In the sixth C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.17 Å. In the seventh C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.17 Å. In the eighth C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.17 Å. In the ninth C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.18 Å. In the tenth C+1.50+ site, C+1.50+ is bonded in a distorted linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.18 Å. In the eleventh C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.17 Å. In the twelfth C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.18 Å. In the thirteenth C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.17 Å. In the fourteenth C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.18 Å. In the fifteenth C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.18 Å. In the sixteenth C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.18 Å. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one C+1.50+ atom. In the second O2- site, O2- is bonded in a distorted linear geometry to one K1+ and one C+1.50+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C+1.50+ atom. In the fourth O2- site, O2- is bonded in a distorted linear geometry to one K1+ and one C+1.50+ atom. In the fifth O2- site, O2- is bonded in a distorted linear geometry to one K1+ and one C+1.50+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C+1.50+ atom. In the seventh O2- site, O2- is bonded in a distorted linear geometry to one K1+ and one C+1.50+ atom. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C+1.50+ atom. In the ninth O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C+1.50+ atom. In the tenth O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one C+1.50+ atom. In the eleventh O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C+1.50+ atom. In the twelfth O2- site, O2- is bonded in a distorted linear geometry to one K1+ and one C+1.50+ atom. In the thirteenth O2- site, O2- is bonded in a distorted linear geometry to one K1+ and one C+1.50+ atom. In the fourteenth O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one C+1.50+ atom. In the fifteenth O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one C+1.50+ atom. In the sixteenth O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C+1.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Materials Data on KCo by Materials Project

KCo is delta Molybdenum Boride-like structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. K is bonded in a 7-coordinate geometry to seven equivalent Co atoms. There are a spread of K–Co bond distances ranging from 3.29–3.71 Å. Co is bonded in a 9-coordinate geometry to seven equivalent K and two equivalent Co atoms. Both Co–Co bond lengths are 2.18 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KCo(CO)4 by Materials Project

KCo(CO)4 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. K1+ is bonded in a distorted pentagonal planar geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.83–3.28 Å. Co1+ is bonded in a tetrahedral geometry to four C+1.50+ atoms. There is two shorter (1.74 Å) and two longer (1.75 Å) Co–C bond length. There are four inequivalent C+1.50+ sites. In the first C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.18 Å. In the second C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.17 Å. In the third C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.17 Å. In the fourth C+1.50+ site, C+1.50+ is bonded in a linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.18 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one C+1.50+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C+1.50+ atom. In the third O2- site, O2- is bonded in a distorted linear geometry to one K1+ and one C+1.50+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C+1.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Physical properties and electronic structure of single-crystal KCo 2 As 2

We present a method for producing high quality KCo 2 As 2 crystals, stable in air and suitable for a variety of measurements. X-ray diffraction, magnetic susceptibility, electrical transport and heat capacity measurements confirm the high quality and an absence of long range magnetic order down to at least 2 K. Residual resistivity values approaching 0.25 µΩ cm are representative of the high quality and low impurity scattering, and a Sommerfeld coefficient γ = 7.3 mJ/mol K 2 signifies weaker correlations than the Fe-based counterparts. Together with Hall effect measurements, angle-resolved photoemission experiments reveal a Fermi surface consisting of electron pockets at the center and corner of the Brillouin zone, in line with theoretical predictions and in contrast to the mixed carrier types of other pnictides with the ThCr 2 Si 2 structure. A large, linear magnetoresistance of 200% at 14 T, together with an observed linear and hyperbolic, rather than parabolic, band dispersions are unusual characteristics of this compound.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials Data on KCo(PO3)3 by Materials Project

KCoP3O9 crystallizes in the hexagonal P-6c2 space group. The structure is three-dimensional. K1+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. All K–O bond lengths are 2.82 Å. Co2+ is bonded to six equivalent O2- atoms to form CoO6 octahedra that share corners with six equivalent PO4 tetrahedra. All Co–O bond lengths are 2.13 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent CoO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 42°. There are a spread of P–O bond distances ranging from 1.50–1.62 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent P5+ atoms. In the second O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one Co2+, and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KCo(N3O4)2 by Materials Project

K(NO2)4CoN2 crystallizes in the orthorhombic P2_12_12_1 space group. The structure is one-dimensional and consists of four diamino cobalt molecules and two K(NO2)4 ribbons oriented in the (1, 0, 0) direction. In each K(NO2)4 ribbon, K1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of K–O bond distances ranging from 2.84–3.11 Å. There are four inequivalent N2+ sites. In the first N2+ site, N2+ is bonded in a bent 120 degrees geometry to two O2- atoms. Both N–O bond lengths are 1.23 Å. In the second N2+ site, N2+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.24 Å) and one longer (1.25 Å) N–O bond length. In the third N2+ site, N2+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.22 Å) and one longer (1.23 Å) N–O bond length. In the fourth N2+ site, N2+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.23 Å) and one longer (1.24 Å) N–O bond length. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one N2+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one K1+ and one N2+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to two equivalent K1+ and one N2+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to two equivalent K1+ and one N2+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one N2+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one N2+ atom. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one N2+ atom. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one N2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KCo(PO3)3 by Materials Project

KCoP3O9 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 6-coordinate geometry to eight O2- atoms. There are a spread of K–O bond distances ranging from 2.62–3.26 Å. In the second K1+ site, K1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of K–O bond distances ranging from 2.73–3.03 Å. There are two inequivalent Co2+ sites. In the first Co2+ site, Co2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Co–O bond distances ranging from 1.95–2.51 Å. In the second Co2+ site, Co2+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Co–O bond distances ranging from 2.03–2.23 Å. There are six 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 CoO6 octahedra and corners with three PO4 tetrahedra. The corner-sharing octahedral tilt angles are 52°. There are a spread of P–O bond distances ranging from 1.49–1.59 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CoO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. There are a spread of P–O bond distances ranging from 1.50–1.72 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CoO6 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 1.49–1.65 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CoO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedral tilt angles are 28°. There are a spread of P–O bond distances ranging from 1.47–1.66 Å. In the fifth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CoO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedral tilt angles are 35°. There are a spread of P–O bond distances ranging from 1.50–1.67 Å. In the sixth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CoO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedral tilt angles are 27°. There are a spread of P–O bond distances ranging from 1.48–1.69 Å. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Co2+, and one P5+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Co2+, and one P5+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+, one Co2+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+, one Co2+, and two P5+ atoms. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one K1+, one Co2+, and one P5+ atom. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Co2+, and one P5+ atom. In the ninth O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one Co2+, and one P5+ atom. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Co2+ and one P5+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the twelfth O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the thirteenth O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one Co2+, and one P5+ atom. In the fourteenth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Co2+, and one P5+ atom. In the fifteenth O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one P5+ atom. In the sixteenth O2- site, O2- is bonded in a bent 120 degrees geometry to one K1+ and two P5+ atoms. In the seventeenth O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the eighteenth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Co2+, and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KCoH3(CO2)3 by Materials Project

KCo(HCOO)3 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. K1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of K–O bond distances ranging from 2.75–2.86 Å. Co2+ is bonded in an octahedral geometry to six O2- atoms. There are a spread of Co–O bond distances ranging from 2.12–2.14 Å. There are two inequivalent C2+ sites. In the first C2+ site, C2+ is bonded in a trigonal planar geometry to one H1+ and two equivalent O2- atoms. The C–H bond length is 1.11 Å. Both C–O bond lengths are 1.27 Å. In the second C2+ site, C2+ is bonded in a trigonal planar geometry to one H1+ and two O2- atoms. The C–H bond length is 1.11 Å. Both C–O bond lengths are 1.27 Å. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C2+ atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C2+ atom. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent K1+, one Co2+, and one C2+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one Co2+, and one C2+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one Co2+, and one C2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Materials Data on KCoH3(CO2)3 by Materials Project

KCo(HCOO)3 crystallizes in the hexagonal P6_322 space group. The structure is three-dimensional. K1+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. All K–O bond lengths are 2.90 Å. Co2+ is bonded in an octahedral geometry to six equivalent O2- atoms. All Co–O bond lengths are 2.14 Å. C2+ is bonded in a trigonal planar geometry to one H1+ and two equivalent O2- atoms. The C–H bond length is 1.10 Å. Both C–O bond lengths are 1.27 Å. H1+ is bonded in a single-bond geometry to one C2+ atom. O2- is bonded in a 3-coordinate geometry to one K1+, one Co2+, and one C2+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS2001

Measurements of Aerosol Vertical Profiles and Optical Properties during INDOEX 1999 Using Micro-Pulse Lidars

Micro-pulse lidar systems (MPL) were used to measure aerosol properties during the Indian Ocean Experiment (INDOEX) 1999 field phase. Measurements were made from two platforms: the NOAA ship RN Ronald H. Brown, and the Kaashidhoo Climate Observatory (KCO) in the Maldives. Sunphotometers were used to provide aerosol optical depths (AOD) needed to calibrate the MPL. This study focuses on the height distribution and optical properties (at 523 nm) of aerosols observed during the campaign. The height of the highest aerosols (top height) was calculated and found to be below 4 km for most of the cruise. The marine boundary layer (MBL) top was calculated and found to be less than 1 km. MPL results were combined with air mass trajectories, radiosonde profiles of temperature and humidity, and aerosol concentration and optical measurements. Humidity varied from approximately 80% near the surface to 50% near the top height during the entire cruise. The average value and standard deviation of aerosol optical parameters were determined for characteristic air mass regimes. Marine aerosols in the absence of any continental influence were found to have an AOD of 0.05 +/- 0.03, an extinction-to-backscatter ratio (S-ratio) of 33 +/- 6 sr, and peak extinction values around 0.05/km (near the MBL top). The marine results are shown to be in agreement with previously measured and expected values. Polluted marine areas over the Indian Ocean, influenced by continental aerosols, had AOD values in excess of 0.2, S-ratios well above 40 sr, and peak extinction values approximately 0.20/km (near the MBL top). The polluted marine results are shown to be similar to previously published values for continental aerosols. Comparisons between MPL derived extinction near the ship (75 m) and extinction calculated at ship-level using scattering measured by a nephelometer and absorption using a PSAP were conducted. The comparisons indicated that the MPL algorithm (using a constant S-ratio throughout the lower troposphere) calculates extinction near the surface in agreement with the ship-level measurements only when the MBL aerosols are well mixed with aerosols above. Finally, a review of the MPL extinction profiles showed that the model of aerosol vertical extinction developed during an earlier INDOEX field campaign (at the Maldives) did not correctly describe the true vertical distribution over the greater Indian Ocean region. Using the average extinction profile and AOD obtained during marine conditions, a new model of aerosol vertical extinction was determined for marine atmospheres over the Indian Ocean. A new model of aerosol vertical extinction for polluted marine atmospheres was also developed using the average extinction profile and AOD obtained during marine conditions influenced by continental aerosols.

Welton, Ellsworth J.↗