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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Tc2As3 by Materials Project

Tc2As3 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent Tc+0.50+ sites. In the first Tc+0.50+ site, Tc+0.50+ is bonded to six As+0.33- atoms to form a mixture of distorted edge, face, and corner-sharing TcAs6 octahedra. The corner-sharing octahedra tilt angles range from 40–60°. There are a spread of Tc–As bond distances ranging from 2.47–2.71 Å. In the second Tc+0.50+ site, Tc+0.50+ is bonded to six As+0.33- atoms to form a mixture of distorted edge, face, and corner-sharing TcAs6 octahedra. The corner-sharing octahedra tilt angles range from 40–59°. There are a spread of Tc–As bond distances ranging from 2.48–2.60 Å. In the third Tc+0.50+ site, Tc+0.50+ is bonded to six As+0.33- atoms to form a mixture of edge, face, and corner-sharing TcAs6 octahedra. The corner-sharing octahedra tilt angles range from 40–60°. There are a spread of Tc–As bond distances ranging from 2.46–2.58 Å. In the fourth Tc+0.50+ site, Tc+0.50+ is bonded to six As+0.33- atoms to form a mixture of edge, face, and corner-sharing TcAs6 octahedra. The corner-sharing octahedra tilt angles range from 40–59°. There are a spread of Tc–As bond distances ranging from 2.45–2.58 Å. There are six inequivalent As+0.33- sites. In the first As+0.33- site, As+0.33- is bonded in a 5-coordinate geometry to four Tc+0.50+ and one As+0.33- atom. The As–As bond length is 2.49 Å. In the second As+0.33- site, As+0.33- is bonded in a 5-coordinate geometry to four Tc+0.50+ and one As+0.33- atom. In the third As+0.33- site, As+0.33- is bonded in a distorted rectangular see-saw-like geometry to four Tc+0.50+ atoms. In the fourth As+0.33- site, As+0.33- is bonded in a 4-coordinate geometry to four Tc+0.50+ atoms. In the fifth As+0.33- site, As+0.33- is bonded in a 5-coordinate geometry to four Tc+0.50+ and one As+0.33- atom. The As–As bond length is 2.82 Å. In the sixth As+0.33- site, As+0.33- is bonded in a 5-coordinate geometry to four Tc+0.50+ and one As+0.33- atom. The As–As bond length is 2.70 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tc2P3 by Materials Project

Tc2P3 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent Tc+0.50+ sites. In the first Tc+0.50+ site, Tc+0.50+ is bonded to six P+0.33- atoms to form a mixture of distorted face, edge, and corner-sharing TcP6 octahedra. The corner-sharing octahedra tilt angles range from 46–60°. There are a spread of Tc–P bond distances ranging from 2.33–2.75 Å. In the second Tc+0.50+ site, Tc+0.50+ is bonded to six P+0.33- atoms to form a mixture of distorted face, edge, and corner-sharing TcP6 octahedra. The corner-sharing octahedra tilt angles range from 43–57°. There are a spread of Tc–P bond distances ranging from 2.30–2.71 Å. In the third Tc+0.50+ site, Tc+0.50+ is bonded to six P+0.33- atoms to form a mixture of face, edge, and corner-sharing TcP6 octahedra. The corner-sharing octahedra tilt angles range from 43–60°. There are a spread of Tc–P bond distances ranging from 2.35–2.45 Å. In the fourth Tc+0.50+ site, Tc+0.50+ is bonded to six P+0.33- atoms to form a mixture of face, edge, and corner-sharing TcP6 octahedra. The corner-sharing octahedra tilt angles range from 46–58°. There are a spread of Tc–P bond distances ranging from 2.35–2.47 Å. There are six inequivalent P+0.33- sites. In the first P+0.33- site, P+0.33- is bonded in a 5-coordinate geometry to four Tc+0.50+ and one P+0.33- atom. The P–P bond length is 2.24 Å. In the second P+0.33- site, P+0.33- is bonded in a 5-coordinate geometry to four Tc+0.50+ and one P+0.33- atom. In the third P+0.33- site, P+0.33- is bonded in a distorted rectangular see-saw-like geometry to four Tc+0.50+ atoms. In the fourth P+0.33- site, P+0.33- is bonded in a 4-coordinate geometry to four Tc+0.50+ atoms. In the fifth P+0.33- site, P+0.33- is bonded in a 5-coordinate geometry to four Tc+0.50+ and one P+0.33- atom. The P–P bond length is 2.42 Å. In the sixth P+0.33- site, P+0.33- is bonded in a 5-coordinate geometry to four Tc+0.50+ and one P+0.33- atom. The P–P bond length is 2.39 Å.

36 MATERIALS SCIENCE↗
NASA NTRSDate not supplied

Assimilation of SMAP Observations Over Land Improves the Simulation and Prediction of Tropical Cyclone Idai

This work is focused on the role of soil moisture in the prediction of tropical cyclones (TCs) approaching land and after landfall. Soil moisture conditions can impact the circulation and structure of an existing tropical cyclone (TC) when part or all of the circulation is over land. For example, dry land surface conditions may lead to faster dissipation of a TC over land (often associated with changes in precipitation structure), whereas very wet conditions may help sustain or in rare cases re-intensify a TC. Moreover, the presence of strong soil moisture gradients may affect the symmetry and development of the TC circulation leading to changes in its over-land track. While the link between soil moisture conditions and TC evolution in proximity to land is relatively well understood in theory, applications of these findings in the context of numerical weather prediction (NWP) have been limited. Here we present a case study that explores the potential of improving TC predictions through an improved soil moisture initialization in an NWP framework. Specifically, we examine the impact of assimilating observations from the NASA Soil Moisture Active Passive (SMAP) mission into the NASA Goddard Earth Observing System (GEOS) global weather model on the prediction of South-West Indian Ocean TC Idai (2019). SMAP provides accurate L-band (1.4 GHz) brightness temperatures (Tb) observations that are sensitive to soil moisture globally and at high revisit times of 2-3 days. It has previously been shown that the assimilation of SMAP Tb observations significantly improves modeled land surface states. Thus, it is expected that SMAP can be used to constrain land surface initial conditions and potentially benefit TC forecasts. Here we present two sets of retrospective forecasts of TC Idai that are compared in an Observing System Experiment framework at ¼ degree resolution: (i) forecasts initialized from an analysis that is comparable to the GEOS operational analysis (without SMAP Tb assimilation) and (ii) forecasts initialized from an analysis that additionally assimilates SMAP brightness temperature observations over land using a weakly-coupled land analysis. We find that the assimilation of SMAP meaningfully improves the representation of TC Idai’s structure as well as the prediction of its intensity and track. The analyzed TC size, as measured by the wind speed radius, is improved by up to 18% in the analysis with SMAP assimilation relative to the control run. The forecast intensity error, measured against the observed intensity, is reduced by up to 23%. At the 1/4-degree resolution used here, GEOS unavoidably under-estimates TC intensity and over-estimates TC size. The SMAP assimilation therefore corrects the model in the right direction, leading to a storm that is more energetic and more compact. Furthermore, we find that the along-track forecast error is reduced by up to 34%, indicating a more accurate propagation speed, which is consistent with the fact that TC speed over land is strongly affected by surface processes. The impact of SMAP assimilation on the forecast cross-track error is neutral. Across the TC forecast skill metrics used here, the improvements from SMAP DA are largest at lead times of 36 to 72 hours, suggesting that the predictability of forecasts at shorter lead times may be dominated by short-term convective processes, while the land and its longer memory gains in importance as a source of predictability on a 2-3 day timescale. We further investigated the underlying mechanisms leading to the skill improvements from SMAP data assimilation by isolating the land areas that directly influence TC Idai using a back trajectory analysis. We find that the assimilation of SMAP leads to wetter soil moisture conditions that cause an increased latent heat flux, which ultimately results in TC analyzed representation that has higher column-integrated total moisture content and total energy compared to the analysis in the control run without SMAP assimilation. Overall, the results highlight that the assimilation of SMAP observations into a global numerical weather prediction model can lead to pronounced improvements of TC predictions. This is a crucial step towards a better mitigation of the socio-economic impact of landfalling TCs and thus safeguarding human lives. Finally, our study presents an event-based approach that assesses the impact of land data assimilation for a particular weather event rather than by globally averaging differences in skill. We argue that global skill assessments – while necessary – can mute the impact of land data assimilation, because the land’s influence on the atmosphere is constrained to certain locations and certain times. Instead, the event-based approach better highlights the true potential of land data assimilation in the context of NWP, especially for extreme events when accurate predictions are critical.

Jana Kolassa↗
NASA NTRSDate not supplied

Assimilation of SMAP Observations Over Land Improves the Simulation and Prediction of Tropical Cyclone Idai

This work is focused on the role of soil moisture in the prediction of tropical cyclones (TCs) approaching land and after landfall. Soil moisture conditions can impact the circulation and structure of an existing tropical cyclone (TC) when part or all of the circulation is over land. For example, dry land surface conditions may lead to faster dissipation of a TC over land (often associated with changes in precipitation structure), whereas very wet conditions may help sustain or in rare cases re-intensify a TC. Moreover, the presence of strong soil moisture gradients may affect the symmetry and development of the TC circulation leading to changes in its over-land track. While the link between soil moisture conditions and TC evolution in proximity to land is relatively well understood in theory, applications of these findings in the context of numerical weather prediction (NWP) have been limited. Here we present a case study that explores the potential of improving TC predictions through an improved soil moisture initialization in an NWP framework. Specifically, we examine the impact of assimilating observations from the NASA Soil Moisture Active Passive (SMAP) mission into the NASA Goddard Earth Observing System (GEOS) global weather model on the prediction of South-West Indian Ocean TC Idai (2019). SMAP provides accurate L-band (1.4 GHz) brightness temperatures (Tb) observations that are sensitive to soil moisture globally and at high revisit times of 2-3 days. It has previously been shown that the assimilation of SMAP Tb observations significantly improves modeled land surface states. Thus, it is expected that SMAP can be used to constrain land surface initial conditions and potentially benefit TC forecasts. Here we present two sets of retrospective forecasts of TC Idai that are compared in an Observing System Experiment framework at ¼ degree resolution: (i) forecasts initialized from an analysis that is comparable to the GEOS operational analysis (without SMAP Tb assimilation) and (ii) forecasts initialized from an analysis that additionally assimilates SMAP brightness temperature observations over land using a weakly-coupled land analysis. We find that the assimilation of SMAP meaningfully improves the representation of TC Idai’s structure as well as the prediction of its intensity and track. The analyzed TC size, as measured by the wind speed radius, is improved by up to 18% in the analysis with SMAP assimilation relative to the control run. The forecast intensity error, measured against the observed intensity, is reduced by up to 23%. At the 1/4-degree resolution used here, GEOS unavoidably under-estimates TC intensity and over-estimates TC size. The SMAP assimilation therefore corrects the model in the right direction, leading to a storm that is more energetic and more compact. Furthermore, we find that the along-track forecast error is reduced by up to 34%, indicating a more accurate propagation speed, which is consistent with the fact that TC speed over land is strongly affected by surface processes. The impact of SMAP assimilation on the forecast cross-track error is neutral. Across the TC forecast skill metrics used here, the improvements from SMAP DA are largest at lead times of 36 to 72 hours, suggesting that the predictability of forecasts at shorter lead times may be dominated by short-term convective processes, while the land and its longer memory gains in importance as a source of predictability on a 2-3 day timescale. We further investigated the underlying mechanisms leading to the skill improvements from SMAP data assimilation by isolating the land areas that directly influence TC Idai using a back trajectory analysis. We find that the assimilation of SMAP leads to wetter soil moisture conditions that cause an increased latent heat flux, which ultimately results in TC analyzed representation that has higher column-integrated total moisture content and total energy compared to the analysis in the control run without SMAP assimilation. Overall, the results highlight that the assimilation of SMAP observations into a global numerical weather prediction model can lead to pronounced improvements of TC predictions. This is a crucial step towards a better mitigation of the socio-economic impact of landfalling TCs and thus safeguarding human lives. Finally, our study presents an event-based approach that assesses the impact of land data assimilation for a particular weather event rather than by globally averaging differences in skill. We argue that global skill assessments – while necessary – can mute the impact of land data assimilation, because the land’s influence on the atmosphere is constrained to certain locations and certain times. Instead, the event-based approach better highlights the true potential of land data assimilation in the context of NWP, especially for extreme events when accurate predictions are critical.

Jana Kolassa↗
DOE OSTI2020

Materials Data on Cs4Tc6S13 by Materials Project

Cs4Tc6S13 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Cs1+ sites. In the first Cs1+ site, Cs1+ is bonded in a 12-coordinate geometry to one Cs1+ and eleven S2- atoms. The Cs–Cs bond length is 3.99 Å. There are a spread of Cs–S bond distances ranging from 3.41–4.25 Å. In the second Cs1+ site, Cs1+ is bonded in a 6-coordinate geometry to one Cs1+ and six S2- atoms. There are a spread of Cs–S bond distances ranging from 3.37–3.69 Å. There are three inequivalent Tc+3.67+ sites. In the first Tc+3.67+ site, Tc+3.67+ is bonded to five S2- atoms to form edge-sharing TcS5 square pyramids. There are a spread of Tc–S bond distances ranging from 2.40–2.58 Å. In the second Tc+3.67+ site, Tc+3.67+ is bonded to five S2- atoms to form a mixture of edge and corner-sharing TcS5 square pyramids. There are a spread of Tc–S bond distances ranging from 2.38–2.48 Å. In the third Tc+3.67+ site, Tc+3.67+ is bonded to five S2- atoms to form edge-sharing TcS5 square pyramids. There are a spread of Tc–S bond distances ranging from 2.40–2.46 Å. There are seven inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to three Cs1+ and three Tc+3.67+ atoms. In the second S2- site, S2- is bonded in a 4-coordinate geometry to one Cs1+ and three Tc+3.67+ atoms. In the third S2- site, S2- is bonded in a 2-coordinate geometry to four Cs1+ and two equivalent Tc+3.67+ atoms. In the fourth S2- site, S2- is bonded in a 6-coordinate geometry to three Cs1+ and three Tc+3.67+ atoms. In the fifth S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Cs1+ and three Tc+3.67+ atoms. In the sixth S2- site, S2- is bonded in a 1-coordinate geometry to three Cs1+ and one Tc+3.67+ atom. In the seventh S2- site, S2- is bonded in a 1-coordinate geometry to three Cs1+, one Tc+3.67+, and one S2- atom. The S–S bond length is 2.13 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K4Tc2H6C8O21 by Materials Project

(K4Tc2C8H5O21)2H2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional and consists of one hydrogen molecule and one K4Tc2C8H5O21 framework. In the K4Tc2C8H5O21 framework, 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 2.79–2.98 Å. In the second 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 2.60–2.86 Å. In the third 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 2.76–3.07 Å. In the fourth K1+ site, K1+ is bonded in a 8-coordinate geometry to one H1+ and seven O2- atoms. The K–H bond length is 2.82 Å. There are a spread of K–O bond distances ranging from 2.78–3.16 Å. There are two inequivalent Tc sites. In the first Tc site, Tc is bonded to six O2- atoms to form distorted edge-sharing TcO6 octahedra. There are a spread of Tc–O bond distances ranging from 1.90–2.10 Å. In the second Tc site, Tc is bonded to six O2- atoms to form distorted edge-sharing TcO6 octahedra. There are a spread of Tc–O bond distances ranging from 1.74–2.14 Å. There are eight inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.24 Å) and one longer (1.31 Å) C–O bond length. In the second C4+ site, C4+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.24 Å) and one longer (1.30 Å) C–O bond length. In the third C4+ site, C4+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.23 Å) and one longer (1.33 Å) C–O bond length. In the fourth C4+ site, C4+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.23 Å) and one longer (1.32 Å) C–O bond length. In the fifth C4+ site, C4+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.25 Å) and one longer (1.31 Å) C–O bond length. In the sixth C4+ site, C4+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.26 Å) and one longer (1.27 Å) C–O bond length. In the seventh C4+ site, C4+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.25 Å) and one longer (1.29 Å) C–O bond length. In the eighth C4+ site, C4+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.23 Å) and one longer (1.31 Å) C–O bond length. There are five inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one K1+ and one O2- atom. The H–O bond length is 0.98 Å. There are twenty-one inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one Tc, and one C4+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one K1+, one Tc, and one C4+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one Tc, and one C4+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Tc, and one C4+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Tc, and one C4+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one K1+ and one Tc atom. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Tc and one C4+ atom. In the eighth O2- site, O2- is bonded in a bent 120 degrees geometry to one Tc and one C4+ atom. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+ and two Tc atoms. In the tenth O2- site, O2- is bonded in a distorted single-bond geometry to two Tc and one H1+ atom. In the eleventh O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one C4+ atom. In the twelfth O2- site, O2- is bonded in a 1-coordinate geometry to two K1+ and one C4+ atom. In the thirteenth O2- site, O2- is bonded in a single-bond geometry to one K1+ and one C4+ atom. In the fourteenth O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C4+ atom. In the fifteenth O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one C4+ atom. In the sixteenth O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one C4+ atom. In the seventeenth O2- site, O2- is bonded in a single-bond geometry to one K1+ and one C4+ atom. In the eighteenth O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C4+ atom. In the nineteenth O2- site, O2- is bonded in a water-like geometry to two K1+ and two H1+ atoms. In the twentieth O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one C4+ atom. In the twenty-first O2- site, O2- is bonded in a water-like geometry to two K1+ and two H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2(TcS2)3 by Materials Project

K2(TcS2)3 crystallizes in the monoclinic C2/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 S2- atoms. There are a spread of K–S bond distances ranging from 3.14–3.54 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 3.17–3.48 Å. In the third 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 3.10–3.62 Å. There are three inequivalent Tc+3.33+ sites. In the first Tc+3.33+ site, Tc+3.33+ is bonded to five S2- atoms to form edge-sharing TcS5 square pyramids. There are a spread of Tc–S bond distances ranging from 2.39–2.50 Å. In the second Tc+3.33+ site, Tc+3.33+ is bonded to five S2- atoms to form a mixture of edge and corner-sharing TcS5 square pyramids. There are a spread of Tc–S bond distances ranging from 2.38–2.51 Å. In the third Tc+3.33+ site, Tc+3.33+ is bonded to five S2- atoms to form a mixture of edge and corner-sharing TcS5 square pyramids. There are a spread of Tc–S bond distances ranging from 2.38–2.51 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to one K1+ and three Tc+3.33+ atoms. In the second S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent K1+ and three Tc+3.33+ atoms. In the third S2- site, S2- is bonded in a 5-coordinate geometry to two K1+ and three Tc+3.33+ atoms. In the fourth S2- site, S2- is bonded in a 6-coordinate geometry to three K1+ and three Tc+3.33+ atoms. In the fifth S2- site, S2- is bonded in a 5-coordinate geometry to three K1+, one Tc+3.33+, and one S2- atom. The S–S bond length is 2.12 Å. In the sixth S2- site, S2- is bonded in a 5-coordinate geometry to three K1+ and two Tc+3.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2(TcSe2)3 by Materials Project

K2(TcSe2)3 crystallizes in the monoclinic C2/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 Se2- atoms. There are a spread of K–Se bond distances ranging from 3.30–3.67 Å. In the second K1+ site, K1+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of K–Se bond distances ranging from 3.32–3.61 Å. In the third K1+ site, K1+ is bonded in a 7-coordinate geometry to eight Se2- atoms. There are a spread of K–Se bond distances ranging from 3.24–3.89 Å. There are three inequivalent Tc+3.33+ sites. In the first Tc+3.33+ site, Tc+3.33+ is bonded to five Se2- atoms to form edge-sharing TcSe5 square pyramids. There are a spread of Tc–Se bond distances ranging from 2.51–2.63 Å. In the second Tc+3.33+ site, Tc+3.33+ is bonded to five Se2- atoms to form a mixture of corner and edge-sharing TcSe5 square pyramids. There are a spread of Tc–Se bond distances ranging from 2.50–2.68 Å. In the third Tc+3.33+ site, Tc+3.33+ is bonded to five Se2- atoms to form a mixture of corner and edge-sharing TcSe5 square pyramids. There are a spread of Tc–Se bond distances ranging from 2.50–2.68 Å. There are six inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to two K1+ and three Tc+3.33+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent K1+ and three Tc+3.33+ atoms. In the third Se2- site, Se2- is bonded in a 5-coordinate geometry to two K1+ and three Tc+3.33+ atoms. In the fourth Se2- site, Se2- is bonded in a 6-coordinate geometry to three K1+ and three Tc+3.33+ atoms. In the fifth Se2- site, Se2- is bonded in a 5-coordinate geometry to three K1+, one Tc+3.33+, and one Se2- atom. The Se–Se bond length is 2.45 Å. In the sixth Se2- site, Se2- is bonded in a 5-coordinate geometry to three K1+ and two Tc+3.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb2(TcSe2)3 by Materials Project

Rb2(TcSe2)3 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are three inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are a spread of Rb–Se bond distances ranging from 3.44–3.72 Å. In the second Rb1+ site, Rb1+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Rb–Se bond distances ranging from 3.40–3.72 Å. In the third Rb1+ site, Rb1+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Rb–Se bond distances ranging from 3.34–3.96 Å. There are three inequivalent Tc+3.33+ sites. In the first Tc+3.33+ site, Tc+3.33+ is bonded to five Se2- atoms to form edge-sharing TcSe5 square pyramids. There are a spread of Tc–Se bond distances ranging from 2.52–2.66 Å. In the second Tc+3.33+ site, Tc+3.33+ is bonded to five Se2- atoms to form a mixture of edge and corner-sharing TcSe5 square pyramids. There are a spread of Tc–Se bond distances ranging from 2.50–2.68 Å. In the third Tc+3.33+ site, Tc+3.33+ is bonded to five Se2- atoms to form a mixture of edge and corner-sharing TcSe5 square pyramids. There are a spread of Tc–Se bond distances ranging from 2.50–2.68 Å. There are six inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to one Rb1+ and three Tc+3.33+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent Rb1+ and three Tc+3.33+ atoms. In the third Se2- site, Se2- is bonded in a 5-coordinate geometry to two Rb1+ and three Tc+3.33+ atoms. In the fourth Se2- site, Se2- is bonded in a 7-coordinate geometry to four Rb1+ and three Tc+3.33+ atoms. In the fifth Se2- site, Se2- is bonded in a 5-coordinate geometry to three Rb1+, one Tc+3.33+, and one Se2- atom. The Se–Se bond length is 2.47 Å. In the sixth Se2- site, Se2- is bonded in a 5-coordinate geometry to three Rb1+ and two Tc+3.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tc3Pd by Materials Project

Tc3Pd is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are three inequivalent Tc+0.67- sites. In the first Tc+0.67- site, Tc+0.67- is bonded to eight Tc+0.67- and four equivalent Pd2+ atoms to form distorted TcTc8Pd4 cuboctahedra that share corners with four equivalent PdTc12 cuboctahedra, corners with fourteen TcTc8Pd4 cuboctahedra, edges with six equivalent PdTc12 cuboctahedra, edges with twelve TcTc8Pd4 cuboctahedra, faces with four equivalent PdTc12 cuboctahedra, and faces with sixteen TcTc8Pd4 cuboctahedra. There are a spread of Tc–Tc bond distances ranging from 2.64–2.91 Å. There are two shorter (2.77 Å) and two longer (2.78 Å) Tc–Pd bond lengths. In the second Tc+0.67- site, Tc+0.67- is bonded to eight equivalent Tc+0.67- and four equivalent Pd2+ atoms to form distorted TcTc8Pd4 cuboctahedra that share corners with four equivalent PdTc12 cuboctahedra, corners with fourteen TcTc8Pd4 cuboctahedra, edges with six equivalent PdTc12 cuboctahedra, edges with twelve equivalent TcTc8Pd4 cuboctahedra, faces with four equivalent PdTc12 cuboctahedra, and faces with sixteen TcTc8Pd4 cuboctahedra. There are two shorter (2.77 Å) and two longer (2.78 Å) Tc–Pd bond lengths. In the third Tc+0.67- site, Tc+0.67- is bonded to eight equivalent Tc+0.67- and four equivalent Pd2+ atoms to form distorted TcTc8Pd4 cuboctahedra that share corners with four equivalent PdTc12 cuboctahedra, corners with fourteen TcTc8Pd4 cuboctahedra, edges with six equivalent PdTc12 cuboctahedra, edges with twelve equivalent TcTc8Pd4 cuboctahedra, faces with four equivalent PdTc12 cuboctahedra, and faces with sixteen TcTc8Pd4 cuboctahedra. There are two shorter (2.77 Å) and two longer (2.78 Å) Tc–Pd bond lengths. Pd2+ is bonded to twelve Tc+0.67- atoms to form PdTc12 cuboctahedra that share corners with six equivalent PdTc12 cuboctahedra, corners with twelve TcTc8Pd4 cuboctahedra, edges with eighteen TcTc8Pd4 cuboctahedra, faces with eight equivalent PdTc12 cuboctahedra, and faces with twelve TcTc8Pd4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tc3C4NCl6 by Materials Project

(TcCl2)3C4N crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of four C4N clusters and four TcCl2 clusters. In each C4N cluster, there are four inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.56 Å. In the second C4+ site, C4+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.68 Å. In the third C4+ site, C4+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.43 Å. In the fourth C4+ site, C4+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.58 Å. N3- is bonded in a 4-coordinate geometry to four C4+ atoms. In each TcCl2 cluster, there are three inequivalent Tc+2.33- sites. In the first Tc+2.33- site, Tc+2.33- is bonded in a distorted T-shaped geometry to three Cl1- atoms. There are a spread of Tc–Cl bond distances ranging from 2.30–2.37 Å. In the second Tc+2.33- site, Tc+2.33- is bonded in a distorted T-shaped geometry to three Cl1- atoms. There are two shorter (2.37 Å) and one longer (2.38 Å) Tc–Cl bond lengths. In the third Tc+2.33- site, Tc+2.33- is bonded in a distorted T-shaped geometry to three Cl1- atoms. There are a spread of Tc–Cl bond distances ranging from 2.31–2.37 Å. There are six inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 2-coordinate geometry to two Tc+2.33- atoms. In the second Cl1- site, Cl1- is bonded in a 2-coordinate geometry to two Tc+2.33- atoms. In the third Cl1- site, Cl1- is bonded in a 2-coordinate geometry to two Tc+2.33- atoms. In the fourth Cl1- site, Cl1- is bonded in a distorted single-bond geometry to one Tc+2.33- atom. In the fifth Cl1- site, Cl1- is bonded in a single-bond geometry to one Tc+2.33- atom. In the sixth Cl1- site, Cl1- is bonded in a single-bond geometry to one Tc+2.33- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Tropical Cyclone Wind Shear-Relative Asymmetry in Reanalyses

Abstract While tropical cyclones (TCs) are axisymmetric vortices to the first order, they often exhibit noteworthy structural asymmetries. These often result from environmental vertical wind shear, which tilts the vortex and induces a wavenumber 1 pattern in the circulation and precipitation fields. Reanalyses and climate models have improved in representing the TC structure and climatology, but their relatively coarse resolution and dependence on parameterized physics cast doubt on their ability to capture the asymmetric TC structure. We perform the most comprehensive process-oriented assessment of TC asymmetry to date in reanalyses. Specifically, we analyze the composite shear-relative TC structure in ERA5 and Climate Forecast System Reanalysis (CFSR), which vary in their resolutions, physical parameterization suites, and data assimilation techniques. These structures are compared with aircraft reconnaissance radar observations. In agreement with the observations, the strongest tangential winds are usually found left-of-shear, while inner core rainfall, ascent, vortex tilt, and low-level inflow are favored directly downshear or in the downshear-left quadrant. Outer rainband convection generally peaks in the downshear-right quadrant. Thermodynamic asymmetries are also apparent, with anomalous low-level moisture right-of-shear, midlevel warmth in the upshear-right quadrant (uptilt), and cloud properties suggestive of a realistic precipitation life cycle from growth to fallout. We also decompose rainfall contributions from the convective parameterization and large-scale cloud schemes and highlight the roles of vorticity advection, buoyancy advection, and diabatic processes in driving asymmetric vertical motions in the inner core and outer rainband regions. Our results suggest that process-level studies of TC asymmetry and TC–wind shear interaction under future warming are viable using climate models. Significance Statement Asymmetries are common in tropical cyclones (TCs), influencing their intensity, track, and hazards. Vertical wind shear often plays a leading-order role in causing these asymmetries. It is uncertain how well asymmetric structures and processes are captured in reanalyses and global climate models (GCMs) with grid spacings of 0.25° and coarser. In this study, we first evaluate TC asymmetry in reanalyses, which have the benefit of being forced by observations. This helps to assess whether the resolutions associated with GCMs sufficiently capture asymmetric structures and processes and motivates upcoming work with free-running GCMs to study how TC asymmetry may change in a warming climate.

Carstens, Jacob D.↗
DOE OSTI2026

HDG-1 Experiment Irradiation Monitoring Data Qualification Final Report

SUMMARY The U.S. Department of Energy (DOE) Advanced Reactor Technologies (ART) Graphite Research and Development (GRD) Program is conducting a series of six experiments to quantify the effects of irradiation on nuclear-grade graphite. This report documents the qualification of irradiation monitoring data for the fifth experiment, High Dose Graphite-1 (HDG-1). Qualified monitoring data are required by the ART program to support the design and licensing of the first high-temperature reactor (HTR) nuclear plant. Data are classified as Qualified if they meet the usage requirements described in the experiment planning and quality assurance (QA) documents, Failed if they do not meet those requirements and provide no usable information, or Trend if they do not fully meet all requirements but still provide useful information subject to an assessment of how any deficiencies may affect a particular use of the data. HDG-1 irradiation began with Advanced Test Reactor (ATR) Cycle 168B on August 24, 2020, and concluded after Cycle 173C on January 27, 2025. The HDG-1 capsule was removed from the reactor core twice—during core internal change (CIC) Cycle 170A and powered axial locator mechanism (PALM) Cycle 172A—to prevent overheating of the graphite specimens during high-power PALM cycles. The capsule was therefore irradiated during a total of seven normal ATR cycles: 168B, 169A, 171A, 171B, 173A, 173B, and 173C. Irradiation monitoring data evaluated in this report include thermocouple (TC) temperature, gas flow rate, gas moisture, gas pressure, specimen load, and graphite stack displacement. Temperature. A total of 14,508,065 TC temperature records were captured. Of these, 13,901,785 (95.8%) are Qualified and 606,280 (4.2%) are Failed. The principal source of failed temperature data was the instrument failure of TC-9 (Zone 2) on June 24, 2024, and TC-10 (Zone 1) on July 5, 2024, near the end of Cycle 173A, which resulted in 595,554 Failed readings. An additional 379 missing values and 10,347 slightly negative values from TC-13 during ATR outages are also Failed. Neither TC-9 nor TC-10 was used as a temperature-control TC, and their failures did not compromise capsule condition monitoring. Correlation analysis of all 13 TCs found no evidence of virtual junction formation. Control chart analysis revealed clear downward drift of approximately 80°C for TC-6 (Zone 3) relative to other stable TCs, and possible downward drift of approximately 60°C for TC-13 relative to the Zone 5 control TC (TC-1), though TC-13 remained consistent with the Zone 2 control TC (TC-12). Gas flow. A total of 20,088,090 gas flow rate records were captured. Of these, 19,941,463 (99.3%) are Qualified and 146,627 (0.7%) are Failed due to missing values. All argon, helium, and total gas flow data were within expected ranges throughout the irradiation. Gas moisture. A total of 1,116,005 outlet gas moisture values were captured. Of these, 1,101,421 (98.7%) are Qualified and 14,584 (1.3%) are Failed, comprising 14,556 out-of-range values and 28 missing values. The out-of-range moisture values exceeded 22,000 ppmv for approximately 1 week at the beginning of Cycle 173A, when accumulated moisture evaporated after the capsule was retrieved from water storage during PALM Cycle 172A and reinserted into the east flux trap. Moisture levels returned to below 25 ppmv for the remaining three cycles, and the transient high-moisture event did not affect the integrity of specimen irradiation. Gas pressure. A total of 7,812,035 gas pressure values were captured. Of these, 6,642,048 (85.0%) are Qualified and 1,169,987 (15.0%) outlet pressure values are Failed, comprising 718,537 zero outlet pressure values due to sensor failure from Cycle 168B through Cycle 171B, 54,550 missing values, and 396,900 too-low outlet pressure values, ranging from 1.1 to 1.6 psia after sensor replacement during Cycle 173A. Load. A total of 6,696,030 load values were captured. Of these, 6,694,580 (99.98%) are Qualified and 1,450 (0.02%) are Failed due to missing values. Applied loads to the six specimen stacks were stable throughout the irradiation. Stack displacement. A total of 6,696,030 displacement values were captured. Of these, 5,713,297 (85.32%) are Qualified and 3,781 (0.06%) are Failed due to missing values. Stack displacement increased consistently throughout the irradiation, reaching approximately 3.08 in. for Channels 5 and 6 by the end of irradiation. 978,952 (14.62%) substantially elevated displacements observed for Channel 6 beginning in Cycle 171A and for Channel 5 beginning in Cycle 173A are assigned Trend status. Raising pressure. A total of 1,115,999 raising pressure values were captured. Of these, 1,115,430 (99.95%) are Qualified and 569 (0.05%) are Failed due to missing values. Ram pressure. A total of 6,696,030 ram pressure values were captured. Of these, 6,692,249 (99.95%) are Qualified and 3,484 (0.05%) are Failed due to missing values. Stack raising was perf

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

A Focused Ion Beam-Scanning Transmission Electron Microscopy with Energy-Dispersive X-ray Spectroscopy Study on Technetium Incorporation within Iron Oxides through Fe(OH) 2 (s) Mineral Transformation

Incorporation of Tc(IV) into iron oxide/hydroxide minerals has been explored and proposed as a promising pathway to preventing Tc(IV) reoxidation to environmentally mobile pertechnetate (TcO 4 - ) and improving long-term immobilization of radioactive technetium-99 (Tc). However, visual evidence evaluating the distribution of Tc(IV) incorporated within iron oxide/hydroxide phases has not been available, until now, despite potential implications on Tc(IV) stability within the host phase. For the purpose of this study Tc(IV) incorporation into iron oxide/hydroxide phases was facilitated via Fe(OH) 2 (s) oxidation and mineral transformation to magnetite (Fe 3 O 4 ). Focused ion beam - scanning transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy (FIB/STEM-EDS) methods were then combined with X-ray diffraction and absorption spectroscopy techniques to characterize and visually demonstrate that, for the first time, Tc(IV) is heterogeneously incorporated into different iron oxide/hydroxide phases as Tc(IV)-incorporated magnetite and/or TcO 2 ·2H 2 O(s) via different incorporation mechanisms. Heterogeneous distribution of Tc(IV) in magnetite suggests either (i) TcO4- is reduced quickly at the magnetite surface and then encapsulated into magnetite during continued octahedral crystal growth, or (ii) Tc(IV) alternatively partitioned into multiple layers of a blocky, plate-like morphological magnetite structure showing stratified Tc. With limited Tc-hematite (Fe 2 O 3 ) incorporation, the results suggest that TcO 2 ·2H 2 O(s) is formed and mainly associated/embedded in fibrous nanometer-sized polycrystalline hematite. This work highlights the power of modern state-of-the-art FIB/STEM-EDS approach to provide essential visual insights of the Tc-iron oxide/hydroxide incorporation and generate reliable mechanism-informed designs for waste forms relying on Tc mineral incorporation.

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

Materials Data on AlTc2Pb by Materials Project

Tc2AlPb crystallizes in the cubic F-43m space group. The structure is three-dimensional. there are two inequivalent Tc sites. In the first Tc site, Tc is bonded to four equivalent Tc and four equivalent Pb atoms to form distorted edge-sharing TcTc4Pb4 tetrahedra. All Tc–Tc bond lengths are 2.82 Å. All Tc–Pb bond lengths are 2.82 Å. In the second Tc site, Tc is bonded in a 4-coordinate geometry to four equivalent Tc, four equivalent Al, and six equivalent Pb atoms. All Tc–Al bond lengths are 2.82 Å. All Tc–Pb bond lengths are 3.25 Å. Al is bonded in a distorted body-centered cubic geometry to four equivalent Tc and four equivalent Pb atoms. All Al–Pb bond lengths are 2.82 Å. Pb is bonded in a distorted body-centered cubic geometry to ten Tc and four equivalent Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tc3Ru by Materials Project

Tc3Ru is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Tc+1.67- sites. In the first Tc+1.67- site, Tc+1.67- is bonded to eight equivalent Tc+1.67- and four equivalent Ru5+ atoms to form distorted TcTc8Ru4 cuboctahedra that share corners with four equivalent RuTc12 cuboctahedra, corners with fourteen equivalent TcTc8Ru4 cuboctahedra, edges with six equivalent RuTc12 cuboctahedra, edges with twelve equivalent TcTc8Ru4 cuboctahedra, faces with four equivalent RuTc12 cuboctahedra, and faces with sixteen TcTc8Ru4 cuboctahedra. There are a spread of Tc–Tc bond distances ranging from 2.69–2.79 Å. There are two shorter (2.71 Å) and two longer (2.76 Å) Tc–Ru bond lengths. In the second Tc+1.67- site, Tc+1.67- is bonded to eight equivalent Tc+1.67- and four equivalent Ru5+ atoms to form distorted TcTc8Ru4 cuboctahedra that share corners with four equivalent RuTc12 cuboctahedra, corners with fourteen TcTc8Ru4 cuboctahedra, edges with six equivalent RuTc12 cuboctahedra, edges with twelve equivalent TcTc8Ru4 cuboctahedra, faces with four equivalent RuTc12 cuboctahedra, and faces with sixteen TcTc8Ru4 cuboctahedra. There are a spread of Tc–Tc bond distances ranging from 2.69–2.79 Å. There are two shorter (2.71 Å) and two longer (2.76 Å) Tc–Ru bond lengths. Ru5+ is bonded to twelve Tc+1.67- atoms to form RuTc12 cuboctahedra that share corners with six equivalent RuTc12 cuboctahedra, corners with twelve TcTc8Ru4 cuboctahedra, edges with eighteen TcTc8Ru4 cuboctahedra, faces with eight equivalent RuTc12 cuboctahedra, and faces with twelve TcTc8Ru4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tc3Pt by Materials Project

Tc3Pt is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Tc+1.67- sites. In the first Tc+1.67- site, Tc+1.67- is bonded to eight Tc+1.67- and four equivalent Pt5+ atoms to form distorted TcTc8Pt4 cuboctahedra that share corners with four equivalent PtTc12 cuboctahedra, corners with fourteen TcTc8Pt4 cuboctahedra, edges with six equivalent PtTc12 cuboctahedra, edges with twelve TcTc8Pt4 cuboctahedra, faces with four equivalent PtTc12 cuboctahedra, and faces with sixteen TcTc8Pt4 cuboctahedra. There are a spread of Tc–Tc bond distances ranging from 2.65–2.91 Å. There are two shorter (2.77 Å) and two longer (2.78 Å) Tc–Pt bond lengths. In the second Tc+1.67- site, Tc+1.67- is bonded to eight Tc+1.67- and four equivalent Pt5+ atoms to form distorted TcTc8Pt4 cuboctahedra that share corners with four equivalent PtTc12 cuboctahedra, corners with fourteen TcTc8Pt4 cuboctahedra, edges with six equivalent PtTc12 cuboctahedra, edges with twelve TcTc8Pt4 cuboctahedra, faces with four equivalent PtTc12 cuboctahedra, and faces with sixteen TcTc8Pt4 cuboctahedra. Both Tc–Tc bond lengths are 2.68 Å. There are two shorter (2.77 Å) and two longer (2.78 Å) Tc–Pt bond lengths. Pt5+ is bonded to twelve Tc+1.67- atoms to form PtTc12 cuboctahedra that share corners with six equivalent PtTc12 cuboctahedra, corners with twelve TcTc8Pt4 cuboctahedra, edges with eighteen TcTc8Pt4 cuboctahedra, faces with eight equivalent PtTc12 cuboctahedra, and faces with twelve TcTc8Pt4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tc3Sn by Materials Project

Tc3Sn is Magnesium-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Tc+1.33- sites. In the first Tc+1.33- site, Tc+1.33- is bonded to eight Tc+1.33- and four equivalent Sn4+ atoms to form TcTc8Sn4 cuboctahedra that share corners with four equivalent SnTc12 cuboctahedra, corners with fourteen TcTc8Sn4 cuboctahedra, edges with six equivalent SnTc12 cuboctahedra, edges with twelve TcTc8Sn4 cuboctahedra, faces with four equivalent SnTc12 cuboctahedra, and faces with sixteen TcTc8Sn4 cuboctahedra. There are a spread of Tc–Tc bond distances ranging from 2.80–2.86 Å. All Tc–Sn bond lengths are 2.83 Å. In the second Tc+1.33- site, Tc+1.33- is bonded to eight Tc+1.33- and four equivalent Sn4+ atoms to form TcTc8Sn4 cuboctahedra that share corners with four equivalent SnTc12 cuboctahedra, corners with fourteen TcTc8Sn4 cuboctahedra, edges with six equivalent SnTc12 cuboctahedra, edges with twelve TcTc8Sn4 cuboctahedra, faces with four equivalent SnTc12 cuboctahedra, and faces with sixteen TcTc8Sn4 cuboctahedra. Both Tc–Tc bond lengths are 2.81 Å. All Tc–Sn bond lengths are 2.83 Å. Sn4+ is bonded to twelve Tc+1.33- atoms to form SnTc12 cuboctahedra that share corners with six equivalent SnTc12 cuboctahedra, corners with twelve TcTc8Sn4 cuboctahedra, edges with eighteen TcTc8Sn4 cuboctahedra, faces with eight equivalent SnTc12 cuboctahedra, and faces with twelve TcTc8Sn4 cuboctahedra.

36 MATERIALS SCIENCE↗