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All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Optical Characterization and 2,525 micron Lasing of Cr(2+):Cd(0.85)Mn(0.15)Te

Transition metal doped solids are of significant current interest for the development of tunable solid-state lasers for the near and mid-infrared (1-4 pm) spectral region. Applications of these lasers include basic research in atomic, molecular, and solid-state physics, optical communication, medicine, and environmental studies of the atmosphere. In transition metal based laser materials, absorption and emission of light arises from electronic transitions between crystal field split energy levels of 3d transition metal ions. The optical spectra generally exhibit broad bands due to the strong interaction between dopant and host (electron-phonon coupling). Broad emission bands offer the prospect of tunable laser activity over a wide wavelength range, e.g. the tuning range of Ti:Sapphire extends from 700-1100 run. The only current transition metal laser operating in the mid-infrared wavelength region (1.8-2.4 micro-m) is CO(2+):MgF2, but its performance is severely limited due to strong nonradiative decay at room temperature. Based on lifetime data, the quantum efficiency is estimated to be less than 3 deg/0 11,21. In general, the probability for non-radiative decay via multi-phonon relaxation increases with decreasing energy gap between ground and excited state. Therefore, efficient transition metal lasers beyond -1.6 micro-m are rare. Recently, tunable laser activity around 2.3 micro-m was observed from Cr doped ZnS and ZnSe. The new lasing center in these materials was identified as Cr(2+) occupying the tetrahedral Zn site. Tetrahedrally coordinated optical centers are rather unusual among transition metal lasers. Their potential usefulness, however, has been demonstrated by the recent development of near infrared laser materials such as Cr:forsterite and Cr:YAG, which are based on tetrahedrally coordinated Cr(4+) ions. According to the Laporte selection rule, electric-dipole transition within the optically active 3d-electron shells are parity forbidden. However, a static acentric electric crystal field or the coupling of asymmetric phonons can force electric-dipole transitions by the admixture of wave functions with opposite parity. Tetrahedral sites lack inversion symmetry which provides the odd-parity field necessary to relax the parity selection rule. Therefore, high absorption and emission cross sections are observed. An enhanced radiative emission rate is also expected to reduce the detrimental effect of non-radiative decay. Motivated by the initial results on Cr doped ZnS and ZnSe, we have started a comprehensive effort to study Cr(2+) doped II-VI semiconductors for solid-state laser applications. In this paper we present the optical properties and the demonstration of mid-infrared lasing from Cr doped Cd(0.85)Mn(0.15)Te.

Davis, V. R.↗
DOE OSTI2020

Materials Data on Mg30CdSnO32 by Materials Project

Mg30CdSnO32 is Molybdenum Carbide MAX Phase-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with two equivalent CdO6 octahedra, corners with two equivalent SnO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.00–2.20 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent SnO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (1.99 Å) and four longer (2.18 Å) Mg–O bond lengths. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.12–2.15 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent CdO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.04 Å) and four longer (2.17 Å) Mg–O bond lengths. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one CdO6 octahedra, an edgeedge with one SnO6 octahedra, and edges with ten MgO6 octahedra. The corner-sharing octahedra tilt angles range from 1–8°. There are four shorter (2.15 Å) and two longer (2.18 Å) Mg–O bond lengths. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 1°. There are four shorter (2.16 Å) and two longer (2.17 Å) Mg–O bond lengths. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one SnO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–7°. There are a spread of Mg–O bond distances ranging from 2.12–2.20 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one CdO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–5°. There are a spread of Mg–O bond distances ranging from 2.14–2.18 Å. Cd2+ is bonded to six O2- atoms to form CdO6 octahedra that share corners with six MgO6 octahedra and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.26 Å) and two longer (2.28 Å) Cd–O bond lengths. Sn2+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with six MgO6 octahedra and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.32 Å) and two longer (2.33 Å) Sn–O bond lengths. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded to five Mg2+ and one Sn2+ atom to form OMg5Sn octahedra that share corners with six OMg5Sn octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. In the second O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six OMg5Sn octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. In the third O2- site, O2- is bonded to five Mg2+ and one Cd2+ atom to form a mixture of edge and corner-sharing OMg5Cd octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the fourth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six equivalent OMg6 octahedra and edges with twelve OMg5Sn octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the fifth O2- site, O2- is bonded to five Mg2+ and one Sn2+ atom to form a mixture of edge and corner-sharing OMg5Sn octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the sixth O2- site, O2- is bonded to five Mg2+ and one Sn2+ atom to form a mixture of edge and corner-sharing OMg5Sn octahedra. The corner-sharing octahedra tilt angles range from 0–3°. There are two shorter (2.18 Å) and two longer (2.20 Å) O–Mg bond lengths. In the seventh O2- site, O2- is bonded to five Mg2+ and one Cd2+ atom to form OMg5Cd octahedra that share corners with six OMg5Sn octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. The O–Mg bond length is 2.06 Å. In the eighth O2- site, O2- is bonded to five Mg2+ and one Cd2+ atom to form OMg5Cd octahedra that share corners with six OMg5Sn octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are a spread of O–Mg bond distances ranging from 2.06–2.18 Å. In the ninth O2- site, O2- is bonded to six Mg2+ atoms to form a mixture of edge and corner-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the tenth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six OMg5Cd octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. In the eleventh O2- site, O2- is bonded to five Mg2+ and one Cd2+ atom to form OMg5Cd octahedra that share corners with six OMg5Sn octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. Both O–Mg bond lengths are 2.18 Å. In the twelfth O2- site, O2- is bonded to five Mg2+ and one Cd2+ atom to form OMg5Cd octahedra that share corners with six OMg5Sn octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are two shorter (2.15 Å) and two longer (2.18 Å) O–Mg bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Identification and quantification of distinct active sites in Hf-Beta zeolites for transfer hydrogenation catalysis

Despite the significant progress made in characterizing different framework heteroatom sites that exist in Lewis acidic zeolites with probe molecule adsorption and spectroscopy, methods to reliably quantify site counts remain indefinite and have been primarily limited to Sn and Ti Lewis acid sites. Here, methods to quantify framework Lewis acidic Hf 4+ sites in zeolite Beta (Hf-Beta) with two Lewis base titrants (pyridine, deuterated acetonitrile) were developed using infrared (IR) spectroscopy. Lewis acid site counts for Hf-Beta zeolites were validated by measuring integrated molar extinction coefficients (IMECs; ε, cm μmol –1 ) on Sn-Beta zeolites using identical Lewis base titrants to benchmark site counts with established literature procedures to quantify Lewis acid sites in Beta zeolites from IR spectra. Highlighting the importance of benchmarking active site counts against well-established experimental protocols, IMECs of CD 3 CN bound to open (ε(Sn; 2316 cm –1 ): 1.80 ± 0.25) and closed (ε(Sn; 2308 cm –1 ): 3.76 ± 0.33) Sn sites were ~1.8x larger than those previously reported while total Lewis acid site counts agreed with those measured by pyridine (ε(Sn; 1451 cm –1 ): 1.58 ± 0.16) on six different Sn-Beta zeolites. IMECs measured for IR peaks reflecting pyridine bound to Lewis acidic Hf sites (ε(Hf; 1448 cm –1 ): 1.54 ± 0.21) and CD 3 CN bound to open (ε(Hf; 2313 cm –1 ): 2.40 ± 0.22) and closed (ε(Hf; 2307 cm –1 ): 3.55 ± 0.41) Hf sites, gave similar counts for the total number of Lewis acidic sites across six Hf-Beta zeolites (Si/Hf = 100–413). Consistent with previous reports with Sn-Beta catalysts where open Sn sites are responsible for catalytic turnover, apparent first and zero-order MPVO rate constants (0.01–1 M cyclohexanone in 2-butanol; per total Hf, 373 K) correlated with the total number of open Hf sites, per total Hf, but not with the total number of closed Hf sites or total Lewis acid site counts. Measured initial MPVO rates (0.1 M cyclohexanone in 2-butanol, per open Hf, 373 K) were ~25x higher on hydrophobic Hf-Beta-F than on hydrophilic Hf-Beta-OH zeolites. Overall, the apparent first-order MPVO rate constants (2-butanol solvent, per open Hf, 373 K) were ~6x higher on Hf-Beta-F than on Hf-Beta-OH zeolites. The characterization methods reported here enable normalization of MPVO turnover rates on Sn- and Hf-Beta zeolites by their number of open sites. Finally, this enables performing quantitative rate comparisons across Lewis acid zeolites of varying active site identity, solvation, and pore topology used in liquid-phase catalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on SrMg30CdO32 by Materials Project

SrMg30CdO32 is alpha Po-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Sr2+ is bonded to six O2- atoms to form SrO6 octahedra that share corners with two equivalent CdO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.23 Å) and four longer (2.34 Å) Sr–O bond lengths. There are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent SrO6 octahedra, corners with four MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 1.98–2.19 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent CdO6 octahedra, corners with four MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.01–2.18 Å. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.12 Å) and two longer (2.17 Å) Mg–O bond lengths. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.13 Å) and two longer (2.16 Å) Mg–O bond lengths. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one SrO6 octahedra, an edgeedge with one CdO6 octahedra, and edges with ten MgO6 octahedra. The corner-sharing octahedra tilt angles range from 1–6°. There are a spread of Mg–O bond distances ranging from 2.09–2.23 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are a spread of Mg–O bond distances ranging from 2.15–2.17 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one SrO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–7°. There are a spread of Mg–O bond distances ranging from 2.12–2.21 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one CdO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–7°. There are a spread of Mg–O bond distances ranging from 2.14–2.18 Å. Cd2+ is bonded to six O2- atoms to form CdO6 octahedra that share corners with two equivalent SrO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.10 Å) and four longer (2.31 Å) Cd–O bond lengths. There are eleven inequivalent O2- sites. In the first O2- site, O2- is bonded to one Sr2+ and five Mg2+ atoms to form OSrMg5 octahedra that share corners with six OMg5Cd octahedra and edges with twelve OSrMg5 octahedra. The corner-sharing octahedra tilt angles range from 0–5°. In the second O2- site, O2- is bonded to five Mg2+ and one Cd2+ atom to form OMg5Cd octahedra that share corners with six OSrMg5 octahedra and edges with twelve OMg5Cd octahedra. The corner-sharing octahedra tilt angles range from 0–5°. In the third O2- site, O2- is bonded to six Mg2+ atoms to form a mixture of corner and edge-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–3°. Both O–Mg bond lengths are 2.17 Å. In the fourth O2- site, O2- is bonded to six Mg2+ atoms to form a mixture of corner and edge-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. In the fifth O2- site, O2- is bonded to one Sr2+ and five Mg2+ atoms to form a mixture of corner and edge-sharing OSrMg5 octahedra. The corner-sharing octahedra tilt angles range from 0–5°. There are a spread of O–Mg bond distances ranging from 1.98–2.21 Å. In the sixth O2- site, O2- is bonded to five Mg2+ and one Cd2+ atom to form a mixture of corner and edge-sharing OMg5Cd octahedra. The corner-sharing octahedra tilt angles range from 0–5°. There are two shorter (2.14 Å) and two longer (2.18 Å) O–Mg bond lengths. In the seventh O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six OMg6 octahedra and edges with twelve OSrMg5 octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the eighth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six equivalent OMg6 octahedra and edges with twelve OSrMg5 octahedra. The corner-sharing octahedra tilt angles range from 1–4°. In the ninth O2- site, O2- is bonded to one Sr2+, four equivalent Mg2+, and one Cd2+ atom to form OSrMg4Cd octahedra that share corners with six OSrMg4Cd octahedra and edges with twelve OSrMg5 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the tenth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six OSrMg4Cd octahedra and edges with twelve OSrMg5 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the eleventh O2- site, O2- is bonded to six Mg2+ atoms to form a mixture of corner and edge-sharing OMg6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cd5Si(PO6)2 by Materials Project

Cd5Si(PO6)2 crystallizes in the orthorhombic P2_12_12_1 space group. The structure is three-dimensional. there are five inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Cd–O bond distances ranging from 2.29–2.81 Å. In the second Cd2+ site, Cd2+ is bonded to seven O2- atoms to form distorted CdO7 pentagonal bipyramids that share a cornercorner with one SiO4 tetrahedra, corners with two equivalent PO4 tetrahedra, an edgeedge with one SiO4 tetrahedra, and an edgeedge with one PO4 tetrahedra. There are a spread of Cd–O bond distances ranging from 2.29–2.75 Å. In the third Cd2+ site, Cd2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Cd–O bond distances ranging from 2.23–2.88 Å. In the fourth Cd2+ site, Cd2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Cd–O bond distances ranging from 2.26–2.51 Å. In the fifth Cd2+ site, Cd2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Cd–O bond distances ranging from 2.22–2.61 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one CdO7 pentagonal bipyramid and an edgeedge with one CdO7 pentagonal bipyramid. There is two shorter (1.65 Å) and two longer (1.67 Å) Si–O bond length. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share an edgeedge with one CdO7 pentagonal bipyramid. There is one shorter (1.55 Å) and three longer (1.56 Å) P–O bond length. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent CdO7 pentagonal bipyramids. There are a spread of P–O bond distances ranging from 1.55–1.57 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Cd2+ and one Si4+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to three Cd2+ and one P5+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to three Cd2+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to two Cd2+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three Cd2+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to two Cd2+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to three Cd2+ and one P5+ atom. In the eighth O2- site, O2- is bonded in a 1-coordinate geometry to three Cd2+ and one Si4+ atom. In the ninth O2- site, O2- is bonded in a distorted single-bond geometry to three Cd2+ and one P5+ atom. In the tenth O2- site, O2- is bonded in a 1-coordinate geometry to three Cd2+ and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a 1-coordinate geometry to three Cd2+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to two Cd2+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na2Cd3Si3O10 by Materials Project

Na2Cd3Si3O10 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Na1+ is bonded to five O2- atoms to form distorted NaO5 square pyramids that share corners with four SiO4 tetrahedra, corners with four equivalent CdO5 trigonal bipyramids, an edgeedge with one CdO6 octahedra, an edgeedge with one NaO5 square pyramid, and an edgeedge with one SiO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.36–2.53 Å. There are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded to five O2- atoms to form distorted CdO5 trigonal bipyramids that share corners with two equivalent CdO6 octahedra, corners with four equivalent NaO5 square pyramids, corners with five SiO4 tetrahedra, corners with two equivalent CdO5 trigonal bipyramids, and an edgeedge with one CdO6 octahedra. The corner-sharing octahedra tilt angles range from 62–77°. There are a spread of Cd–O bond distances ranging from 2.26–2.38 Å. In the second Cd2+ site, Cd2+ is bonded to six O2- atoms to form CdO6 octahedra that share corners with two equivalent SiO4 tetrahedra, corners with four equivalent CdO5 trigonal bipyramids, edges with two equivalent NaO5 square pyramids, edges with two equivalent SiO4 tetrahedra, and edges with two equivalent CdO5 trigonal bipyramids. There are a spread of Cd–O bond distances ranging from 2.26–2.44 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one CdO6 octahedra, a cornercorner with one NaO5 square pyramid, a cornercorner with one SiO4 tetrahedra, corners with four equivalent CdO5 trigonal bipyramids, an edgeedge with one CdO6 octahedra, and an edgeedge with one NaO5 square pyramid. The corner-sharing octahedral tilt angles are 53°. There are a spread of Si–O bond distances ranging from 1.63–1.68 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with six equivalent NaO5 square pyramids, corners with two equivalent SiO4 tetrahedra, and corners with two equivalent CdO5 trigonal bipyramids. There is two shorter (1.63 Å) and two longer (1.68 Å) Si–O bond length. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Cd2+, and one Si4+ atom. In the second O2- site, O2- is bonded to three Cd2+ and one Si4+ atom to form distorted OCd3Si trigonal pyramids that share corners with two equivalent ONa2CdSi tetrahedra and corners with three equivalent OCd3Si trigonal pyramids. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded to two equivalent Na1+, one Cd2+, and one Si4+ atom to form distorted ONa2CdSi tetrahedra that share a cornercorner with one ONa2CdSi tetrahedra, corners with two equivalent OCd3Si trigonal pyramids, and an edgeedge with one ONa2CdSi tetrahedra. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Na1+, two Cd2+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1971

Investigation of electrode materials for alkaline batteries

A number of amalgam electrode systems were investigated for possible use as high rate anodes and cathodes. The systems examined include: lithium, sodium, and potassium in Group 1, magnesium, calcium, and barium in Group 2, aluminum in Group 3, lead in Group 4, copper in Group 1b, and zinc and cadmium in Group 2b. The K(Hg) and Na(Hg) anodes in 10 VF and 15 VF (an unambiguous expression of concentration that indicates the number of formula weights of solute dissolved in a liter of solution) hydroxide solutions have proven satisfactory; some of these have produced current densities of more than 8 A/sq cm. None of the amalgam cathodes have approached this performance although the TI(Hg) has delivered 1 A/sq cm. Se(Hg) and Te(Hg) cathodes have given very stable discharges. Zn(Hg) and Cd(Hg) electrodes did not show good high rate characteristics, 200 to 300 mA/sq cm being about the maximum current densities obtainable. Both anodes are charged through a two-step process in which M(Hg) is first formed electrochemically and subsequently reduces Zn(II or Cd(II) to form the corresponding amalgam. The second step is extremely rapid for zinc and very slow for cadmium.

Arcand, G. M.↗
DOE OSTI2023

Assessment of deep levels with selenium concentration in Cd 1–x Zn x Te 1–y Se y room temperature detector materials

Incorporation of Se into Cd 1–x Zn x Te (CZT) to form the quaternary compound semiconductor Cd 1–x Zn x Te 1–y Se y (CZTS) has proven to be an effective solution for compensating the major flaws associated with CZT, including poor homogeneity and high concentrations of electronically active deep levels that limit the performance of CZT detectors. In order to investigate how deep levels are affected by the Se concentration in CZTS, we performed photoinduced current transient spectroscopy (PICTS) measurements on CZTS crystals grown by the traveling heater method (THM) with 10% atomic Zn and varying atomic percentage of Se from 1.5% to 7.0%. The PICTS scans for up to 4% Se showed an exponential reduction in the capture cross section of deep levels associated with Te secondary phases in conjunction with an increase in a deep level positioned near the mid-gap, which initially increases the electron trapping time before degrading again at higher Se concentrations. The PICTS peaks present in 7% Se were anomalous relative to the other crystals and are expected to originate from transition metal impurities found in the lower-purity CdSe precursor material.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na2ZrCd(CO3)8 by Materials Project

Na2ZrCd(C2O5)4(O2)2 crystallizes in the hexagonal P6_222 space group. The structure is three-dimensional and consists of twelve water molecules and one Na2ZrCd(C2O5)4 framework. In the Na2ZrCd(C2O5)4 framework, there are two inequivalent Na sites. In the first Na site, Na is bonded in a 8-coordinate geometry to eight O atoms. There are four shorter (2.58 Å) and four longer (2.66 Å) Na–O bond lengths. In the second Na site, Na is bonded in a 8-coordinate geometry to eight O atoms. There are four shorter (2.53 Å) and four longer (2.67 Å) Na–O bond lengths. Zr is bonded in a 8-coordinate geometry to eight O atoms. There are four shorter (2.21 Å) and four longer (2.25 Å) Zr–O bond lengths. Cd is bonded in a 8-coordinate geometry to eight O atoms. There are four shorter (2.40 Å) and four longer (2.43 Å) Cd–O bond lengths. There are two inequivalent C sites. In the first C site, C is bonded in a distorted bent 120 degrees geometry to two O atoms. There is one shorter (1.25 Å) and one longer (1.28 Å) C–O bond length. In the second C site, C is bonded in a distorted bent 120 degrees geometry to two O atoms. There is one shorter (1.24 Å) and one longer (1.28 Å) C–O bond length. There are five inequivalent O sites. In the first O site, O is bonded in a distorted single-bond geometry to one Na, one Cd, and one C atom. In the second O site, O is bonded in a bent 120 degrees geometry to one Zr and one C atom. In the third O site, O is bonded in a bent 120 degrees geometry to two Na atoms. In the fourth O site, O is bonded in a distorted trigonal planar geometry to one Na, one Zr, and one C atom. In the fifth O site, O is bonded in a distorted bent 120 degrees geometry to one Cd and one C atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na2MnCdFe(PO4)3 by Materials Project

Na2MnFeCd(PO4)3 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to eight O2- atoms to form distorted NaO8 hexagonal bipyramids that share corners with two equivalent PO4 tetrahedra, an edgeedge with one CdO6 octahedra, edges with two equivalent MnO6 octahedra, edges with two equivalent FeO6 octahedra, and edges with three PO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.56–2.89 Å. In the second Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.35–2.75 Å. In the third Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.35–2.63 Å. Mn2+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with six PO4 tetrahedra, an edgeedge with one NaO8 hexagonal bipyramid, an edgeedge with one FeO6 octahedra, and an edgeedge with one CdO6 octahedra. There are a spread of Mn–O bond distances ranging from 2.08–2.35 Å. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six PO4 tetrahedra, an edgeedge with one NaO8 hexagonal bipyramid, and an edgeedge with one MnO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.97–2.21 Å. There are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded to six O2- atoms to form distorted CdO6 octahedra that share corners with six PO4 tetrahedra, an edgeedge with one NaO8 hexagonal bipyramid, and edges with two equivalent MnO6 octahedra. There are a spread of Cd–O bond distances ranging from 2.32–2.36 Å. In the second Cd2+ site, Cd2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Cd–O bond distances ranging from 2.30–2.42 Å. There are four inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NaO8 hexagonal bipyramid, a cornercorner with one CdO6 octahedra, corners with two equivalent MnO6 octahedra, and corners with two equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 37–60°. There are a spread of P–O bond distances ranging from 1.55–1.59 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CdO6 octahedra, corners with two equivalent MnO6 octahedra, corners with two equivalent FeO6 octahedra, and an edgeedge with one NaO8 hexagonal bipyramid. The corner-sharing octahedra tilt angles range from 41–59°. There are a spread of P–O bond distances ranging from 1.54–1.58 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent MnO6 octahedra, corners with two equivalent FeO6 octahedra, and an edgeedge with one NaO8 hexagonal bipyramid. The corner-sharing octahedral tilt angles are 50°. There is two shorter (1.53 Å) and two longer (1.58 Å) P–O bond length. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent MnO6 octahedra, corners with two equivalent FeO6 octahedra, and corners with two equivalent CdO6 octahedra. The corner-sharing octahedra tilt angles range from 49–63°. There is two shorter (1.55 Å) and two longer (1.56 Å) P–O bond length. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Mn2+, and one P5+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Fe3+, and one P5+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, one Mn2+, one Cd2+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Fe3+, one Cd2+, and one P5+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, one Mn2+, one Cd2+, and one P5+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Fe3+, one Cd2+, and one P5+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+, one Cd2+, and one P5+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+, one Cd2+, and one P5+ atom. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+, one Mn2+, and one P5+ atom. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Fe3+, and one P5+ atom. In the eleventh O2- site, O2- is bonded in a 3-coordinate geometry to one Mn2+, one Fe3+, and one P5+ atom. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to one Mn2+, one Fe3+, and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaVCdO4 by Materials Project

NaCdVO4 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Na1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are two shorter (2.29 Å) and two longer (2.49 Å) Na–O bond lengths. V5+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with six equivalent CdO6 octahedra. The corner-sharing octahedra tilt angles range from 44–53°. There is two shorter (1.72 Å) and two longer (1.78 Å) V–O bond length. Cd2+ is bonded to six O2- atoms to form CdO6 octahedra that share corners with six equivalent VO4 tetrahedra and edges with two equivalent CdO6 octahedra. There are two shorter (2.28 Å) and four longer (2.38 Å) Cd–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, one V5+, and two equivalent Cd2+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one V5+, and one Cd2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Diazirine-based photo-crosslinkers for defect free fabrication of solution processed organic light-emitting diodes

The fabrication of solution deposited OLEDs is fraught with difficulties, largely due to the interlayer mixing and surface erosion during sequential deposition of the layers. We demonstrate that these problems can be circumvented by using photopolymerizable diazirine-based cross-linker capable of converting soluble organic materials into highly cross-linked insoluble networks. 3-Trifluoromethyl(aryl)diazirines photolyze readily upon the 10–15 min exposure of 365 nm UV irradiation to generate carbenes, which react with polymers or small molecules via C–H bond insertion producing highly cross-linked materials. This photo-generated cross-linking does not require any catalyst, initiator or short-wavelength UV light and is performed at room temperature, releasing molecular nitrogen as the only byproduct. To show the cross-linked polymer layers do not display inter-layer mixing, we deposited red-emitting regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) over cross-linked (10% cross-linker) blue emitting dioctyl polyfluorene (PFO) layer. The overlaid layers showed clear and well-defined boundary with no interlayer mixing. The surface morphology of the solution deposited layers was investigated by AFM to show that the cross-linked layers exhibited significant decrease in surface roughness. This is also shown on the example of the hole transporting material 4,4'-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl (NPB) which displayed roughness average to decrease from 6.4 nm to 1.0 nm. The effect of decreased surface roughness on the performance of phosphorescent OLEDs was investigated by fabricating devices with configuration of ITO/PEDOT:PSS/NPB:(0%/5%/10%) cross-linker/MCP:6% Ir(mppy) 3 /TPBI/CsF/Al. Furthermore, following the diazirine-mediated cross-linking, the OLEDs displayed a decrease in turn-on voltage from 3.8 V to 3.0 V along with a six-fold enhancement of external quantum efficiency (EQE max ) from 1.1% to 6.8% and maximum luminous efficiency increase from 3.8 cd A -1 to 22.9 cd A -1 . These results demonstrate that the simple diazirine mediated photo-cross-linking using mild conditions compatible with organic layers is a promising strategy for improving the performance of the solution-processed OLEDs.

36 MATERIALS SCIENCE↗
NASA NTRS2005

Carbon Dynamics in Vegetation and Soils

The overall goals of CD-08 team in Phase I were to quantify the contributions of different components of the carbon cycle to overall ecosystem carbon balance in Amazonian tropical forests and to undertake process studies at a number of sites along the eastern LBA transect to understand how and why these fluxes vary with site, season, and year. We divided this work into a number of specific tasks: (1) determining the average rate (and variability) of tree growth over the past 3 decades; (2) determining age demographics of tree populations, using radiocarbon to determine tree age; (3) assessing the rate of production and decomposition of dead wood debris; (4) determining turnover rates for organic matter in soils and the mean age of C respired from soil using radiocarbon measurements; and (5) comparing our results with models and constructing models to predict the potential of tropical forests to function as sources or sinks of C. This report summarizes the considerable progress made towards our original goals, which have led to increased understanding of the potential for central Amazon forests to act as sources or sinks of carbon with altered productivity. The overall picture of tropical forest C dynamics emerging from our Phase I studies suggests that the fraction of gross primary production allocated to growth in these forests is only 25-30%, as opposed to the 50% assumed by many ecosystem models. Consequent slow tree growth rates mean greater mean tree age for a given diameter, as reflected in our measurements and models of tree age. Radiocarbon measurements in leaf and root litter suggest that carbon stays in living tree biomass for several years up to a decade before being added to soils, where decomposition is rapid. The time lags predicted from 14C, when coupled with climate variation on similar time scales, can lead to significant interannual variation in net ecosystem C exchange.

Trumbore, Susan↗
DOE OSTI2020

Materials Data on Na2Cd2Fe(PO4)3 by Materials Project

Na2FeCd2(PO4)3 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.31–2.76 Å. In the second Na1+ site, Na1+ is bonded to eight O2- atoms to form distorted NaO8 hexagonal bipyramids that share corners with two equivalent PO4 tetrahedra, edges with two equivalent FeO6 octahedra, edges with three CdO6 octahedra, and edges with three PO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.58–2.83 Å. In the third Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.33–2.69 Å. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six PO4 tetrahedra, an edgeedge with one NaO8 hexagonal bipyramid, and an edgeedge with one CdO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.98–2.17 Å. There are three inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded to six O2- atoms to form distorted CdO6 octahedra that share corners with six PO4 tetrahedra, an edgeedge with one NaO8 hexagonal bipyramid, an edgeedge with one FeO6 octahedra, and an edgeedge with one CdO6 octahedra. There are a spread of Cd–O bond distances ranging from 2.18–2.40 Å. In the second Cd2+ site, Cd2+ is bonded to six O2- atoms to form distorted CdO6 octahedra that share corners with six PO4 tetrahedra, an edgeedge with one NaO8 hexagonal bipyramid, and edges with two equivalent CdO6 octahedra. There are a spread of Cd–O bond distances ranging from 2.32–2.39 Å. In the third Cd2+ site, Cd2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Cd–O bond distances ranging from 2.31–2.88 Å. There are four inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent FeO6 octahedra and corners with four CdO6 octahedra. The corner-sharing octahedra tilt angles range from 49–61°. There is two shorter (1.55 Å) and two longer (1.57 Å) P–O bond length. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent FeO6 octahedra, corners with two equivalent CdO6 octahedra, and an edgeedge with one NaO8 hexagonal bipyramid. The corner-sharing octahedra tilt angles range from 47–54°. There is two shorter (1.53 Å) and two longer (1.58 Å) P–O bond length. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NaO8 hexagonal bipyramid, corners with two equivalent FeO6 octahedra, and corners with three CdO6 octahedra. The corner-sharing octahedra tilt angles range from 35–62°. There are a spread of P–O bond distances ranging from 1.55–1.59 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent FeO6 octahedra, corners with three CdO6 octahedra, and an edgeedge with one NaO8 hexagonal bipyramid. The corner-sharing octahedra tilt angles range from 40–64°. There are a spread of P–O bond distances ranging from 1.54–1.58 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Fe3+, and one P5+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, two Cd2+, and one P5+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, two Cd2+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Fe3+, one Cd2+, and one P5+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Cd2+, and one P5+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Fe3+, and one P5+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+, one Cd2+, and one P5+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+, one Cd2+, and one P5+ atom. In the ninth O2- site, O2- is bonded in a 1-coordinate geometry to one Fe3+, one Cd2+, and one P5+ atom. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to one Fe3+, one Cd2+, and one P5+ atom. In the eleventh O2- site, O2- is bonded in a 3-coordinate geometry to one Fe3+, one Cd2+, and one P5+ atom. In the twelfth O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, two Cd2+, and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CdSiO3 by Materials Project

CdSiO3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are three inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded to six O2- atoms to form distorted CdO6 octahedra that share corners with six SiO4 tetrahedra and edges with six CdO6 octahedra. There are a spread of Cd–O bond distances ranging from 2.34–2.42 Å. In the second Cd2+ site, Cd2+ is bonded to six O2- atoms to form distorted CdO6 octahedra that share corners with five SiO4 tetrahedra, edges with four CdO6 octahedra, and an edgeedge with one SiO4 tetrahedra. There are a spread of Cd–O bond distances ranging from 2.21–2.56 Å. In the third Cd2+ site, Cd2+ is bonded to six O2- atoms to form distorted CdO6 octahedra that share corners with five SiO4 tetrahedra, edges with four CdO6 octahedra, and an edgeedge with one SiO4 tetrahedra. There are a spread of Cd–O bond distances ranging from 2.27–2.50 Å. There are three inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with six CdO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 44–75°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with six CdO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 44–74°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four CdO6 octahedra, corners with two SiO4 tetrahedra, and edges with two CdO6 octahedra. The corner-sharing octahedra tilt angles range from 14–69°. There are a spread of Si–O bond distances ranging from 1.63–1.68 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Cd2+ and one Si4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Cd2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Cd2+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Cd2+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Cd2+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one Cd2+ and two Si4+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Cd2+ and one Si4+ atom. In the ninth O2- site, O2- is bonded to three Cd2+ and one Si4+ atom to form distorted corner-sharing OCd3Si tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Conceptual Design of Passive Neutron Albedo Reactivity and Active Neutron Albedo Reactivity Instruments for Various Arrangements of Pebble Bed Reactor Pebbles

MCNP6 simulations were performed to assess the anticipated capability of the Passive Neutron Albedo Reactivity technique for nuclear safeguards measurements of irradiated pebble/pebbles. Two physical setups were examined. One with a single pebble of three different burnups and one with 27 pebbles in a cube. For all cases the sensitivity to removing all the fissile material was examined. For both of the physical setups, 4 assay cases were examined: (a) singles count rates for which the only source neutrons were the inherent neutrons in the fuel, (b) singles count rates again except this time two relatively weak AmLi sources were placed above and below the top central pebble and the combined effect of both neutron source terms were examined, (c) doubles count rates for which the only source neutrons were the inherent neutrons in the fuel, and (d) doubles count rates again except this time two relatively weak AmLi sources were placed above and below the top central pebble and the combined effect of both neutron source terms were examined. Finally, a few parameters such as Cd near the 3 He tubes were perturbed to see if the results could be improved.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Microbial potentiometric sensor technology for real-time detecting and monitoring of toxic metals in aquatic matrices

Considering that toxic metals can affect metabolic processes in microorganisms adversely, it can be hypothesized that these metals in water matrices would induce a decrease in metabolic activity of the biofilm microorganisms populating the surface of a sensing electrode, which could be registered as a change in the open-circuit potential (OCP) generated by the biofilm microorganisms. The goal of this study was to test this hypothesis and demonstrate the underlying principle that microbial potentiometric sensor (MPS) technology could be used for long-term and real-time monitoring and detection of rapid changes in metal concentrations in realistic aquatic environments. To address the goal, four objective were addressed: (1) a batch reactor with three graphite-based MPS electrodes was fabricated; (2) a set of single-ion solutions and one multiple ion solution were prepared reflecting realistic concentrations of metals found in electroplating wastewaters; (3) the responses of the MPS to the simultaneous presence of multiple toxic metal ions in a single solution were measured; and (4) the changes of the MPS signals to the presence of individual metal ion solutions were examined. While the hypothesis was validated, the study also revealed that the MPS was sufficiently sensitive to not only detect, but also quantify, toxic metal ion concentrations in aqueous solutions. The coefficients of determination, which were R 2 > 0.995, and responsiveness of <1 μmol/L for some toxic metal cations, strongly support the performance of MPS technology in the echelons of expensive analytical tools capable detecting and measuring trace elements.The magnitude of the MPS response was toxic metal specific. When the molar concertation normalizes the inhibition portion of the signal area, the assessed sensitivity order was: Se>Cd>Pb>Ag>Ni> Zn. The study provides valuable information for enforcement agents, environmental professionals, and wastewater treatment operators, so toxic metal pollution and its detrimental impacts can be prevented and mitigated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Lifetimes of excited states in $^{16}$C as a benchmark for ab initio developments

Lifetimes of higher-lying states ($2_2^+$ and $4_1^+$) in 16 C have been measured, employing the Gammasphere and Microball detector arrays, as key observables to test and refine ab initio calculations based on interactions developed within chiral Effective Field Theory. The presented experimental constraints to these lifetimes of $\tau ({2_2^+}) = [244, 446]\,~\textrm{fs}$ and $\tau ({4_1^+}) = [1.8, 4]\,~\textrm{ps}$, combined with previous results on the lifetime of the $2_1^+$ state of 16 C, provide a rather complete set of key observables to benchmark the theoretical developments. We present No-Core Shell-Model calculations using state-of-the-art chiral 2- (NN) and 3-nucleon (3N) interactions at next-to-next-to-next-to-leading order for both the NN and the 3N contributions and a generalized natural-orbital basis (instead of the conventional harmonic-oscillator single-particle basis) which reproduce, for the first time, the experimental findings remarkably well. The level of agreement of the new calculations as compared to the CD-Bonn meson-exchange NN interaction is notable and presents a critical benchmark for theory.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗