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NASA NTRS2010

Human Factors Research for Space Exploration: Measurement, Modeling, and Mitigation

As part of NASA's Human Research Program, the Space Human Factors Engineering Project serves as the bridge between Human Factors research and Human Spaceflight applications. Our goal is to be responsive to the operational community while addressing issues at a sufficient level of abstraction to ensure that our tools and solutions generalize beyond the point design. In this panel, representatives from four of our research domains will discuss the challenges they face in solving current problems while also enabling future capabilities. Historically, engineering-dominated organizations have tended to view good Human Factors (HF) as a desire rather than a requirement in system design and development. Our field has made significant gains in the past decade, however; the Department of Defense, for example, now recognizes Human-System Integration (HSI), of which HF is a component, as an integral part of their divisions hardware acquisition processes. And our own agency was far more accepting of HF/HSI requirements during the most recent vehicle systems definition than in any prior cycle. Nonetheless, HF subject matter experts at NASA often find themselves in catch up mode... coping with legacy systems (hardware and software) and procedures that were designed with little regard for the human element, and too often with an attitude of we can deal with any operator issues during training. Our challenge, then, is to segregate the true knowledge gaps in Space Human Factors from the prior failures to incorporate best (or even good) HF design principles. Further, we strive to extract the overarching core HF issues from the point-design-specific concerns that capture the operators (and managers) attention. Generally, our approach embraces a 3M approach to Human Factors: Measurement, Modeling, and Mitigation. Our first step is to measure human performance, to move from subjective anecdotes to objective, quantified data. Next we model the phenomenon, using appropriate methods in our field, modifying them to suit the unique aspects of the space environment. Finally, we develop technologies, tools, and procedures to mitigate the decrements in human performance and capabilities that occur in space environments. When successful, we decrease risks to crew safety and to mission success. When extremely successful (or lucky), we devise generalizable solutions that advance the state of our practice. Our panel is composed of researchers from diverse domains of our project... from different boxes, if you will, of the Human Factors Analysis and Classification System (HFACS).

Kaiser, Mary K.↗

NASA NTRSDate not supplied

The Effects of Autogenic Feedback Training Exercise on Heart Rate Variability

INTRODUCTION: The development of Motion Sickness (MS) symptoms is correlated with increased sympathetic influence and irregular patterns of vagal activity. Such autonomic actions can be characterized by indices of heart rate variability (HRV), which reflect autonomic balance through neurocardiac function. Nonpharmacological interventions aimed at attenuating MS symptoms may therefore produce an effect on HRV. One such intervention that has been shown to mitigate MS symptoms is Autogenic Feedback Training Exercise (AFTE), which combines principles of autogenic therapy and biofeedback. AFTE teaches individuals to manipulate various physiological parameters in provocative environments and shows promise as a potential MS intervention in military aviators. The effects of AFTE on HRV have not previously been examined. Understanding HRV changes following AFTE may help to elucidate its indirect effects and inform its implementation for MS mitigation. METHODS: Twenty-four subjects received 2 hours of AFTE over 4 days. Pre- and post-AFTE rotating chair tests, which included stationary periods of baseline data, were conducted to evaluate the effects of AFTE. HRV data were recorded by SOMNOtouch™ NIBP. Post hoc analysis of pre- and post-AFTE short-term HRV (RMSSD, LF, HF, LF/HF) was performed. RESULTS: RMSSD, HF, and LF/HF were not significantly changed following AFTE. However, LF showed a statistically significant (p=0.015) decrease following AFTE. DISCUSSION: AFTE prescribes a respiratory rate of 15 breaths per minute (BPM), which is typically faster than participants’ pre-AFTE BPM (M=12.65). Healthy individuals can increase respiratory sinus arrhythmia (RSA) by slow, deep breathing. However, increasing the respiratory rate to 15 BPM may decrease RSA and subsequently HF. Increasing RSA potentially negates any influence of AFTE on HF, resulting in no significant change. RMSSD is correlated with HF power and was likewise not affected by AFTE. LF power, however, decreased significantly following AFTE, potentially indicating a lower sympathetic response in the post-AFTE measurement.

motion sickness↗

NASA NTRSDate not supplied

Identifying Human Factors Research for Unmanned Aircraft Systems and Advanced Air Mobility

This paper identifies some of the key human factors (HF) challenges when integrating Unmanned Aircraft Systems (UAS) and Advanced Air Mobility (AAM) into the civil airspace. Unique HF considerations—those which are derived from the key differentiating aspects of UAS/AAM compared to conventional aviation—are the primary basis for identifying HF research opportunities. By identifying what makes UAS and AAM fundamentally different from conventional aviation, from a human integration perspective, HF research can be targeted to effectively inform best practices, standards, policy, guidance, and regulations associated with aircraft and air traffic systems and operations. HF research areas are discussed within the following topic areas: Sustained low-altitude operations; loss of natural sensing; novel aircraft; novel operations; link management and lost link; link performance; distributed pilot teams; and increased automation. The identified research descriptions are intended to serve as illustrative examples of what research is fundamental, and why. They are not intended to prescribe, prioritize or exclude research.

AAM↗

NASA NTRSDate not supplied

Identifying Human Factors Research for Unmanned Aircraft Systems (UAS) and Advanced Air Mobility (AAM)

AAM↗

NASA NTRS2025

Habitability and Human Factors Assessment (iSHORT, SHAQ, and SHU)

BACKGROUND As long-duration off-planet habitats become a reality, a consideration of habitability and human factors (HF) is crucial. The habitat is more than just a place to live and work. It is also the crew’s perception of the space, and the psychological impacts of size, layout, and usage over time; all of which can support or strain behavioral health and performance (BHP). A previous International Space Station (ISS) habitability study used the iSHORT (Space Habitability Observation Reporting Tool) to collect detailed data about habitability and human factors and inform NASA Standards. Of the previous iSHORT study, only one of the six ISS subjects had a duration of one year; all other ISS and ground analog subjects had shorter mission durations from one week to six months. It is necessary to collect new data with a focus on long-duration exploration missions of > 6 months and on planetary surface habitat design. New data is also needed to compare the iSHORT to other habitability measures. One measure, the SHAQ (Subjective Habitability and Acceptability Questionnaire), assesses the intersection of psychology and habitability. Another complementary measure, the Scale for Habitat Usability (SHU), is a brief subjective scale that captures how habitat design impacts perceived usability of the built environment in relation to task performance. OBJECTIVE Our study aims to (1) understand how individual well-being and team dynamics may relate to HF concerns over time, (2) capture how habitability and HF change over time, (3) compare the three habitability measures (iSHORT, SHAQ, SHU), (4) assess habitats to capture HF design concerns and related BHP impacts of a planetary habitat, and (5) inform future standards for HF design. METHOD Data are being collected on crews living and working in long-duration spaceflight analogs. Individual-level data collections are repeated at regular intervals throughout the missions on several habitat areas, activities, and key equipment (i.e., points of interest). These points of interest (POIs) include the kitchen/galley, crew quarters, and other work and living areas. Assessments include evaluations of privacy, comfort, convenience, control, efficiency, and social density through the lens of subsequent outcomes like sleep, individual performance, group activities performance, stress, mood, and social interactions. Pre- and post-mission evaluations will also allow comparison with homes, pre- and post-mission hotels, and a retrospective reflection of living and working in a long-duration analog. INITIAL DATA COLLECTIONS In this poster, we will describe the measures and data yield. Since the research protocol was designed, the study team has collected iSHORT Standalone four times, nine collections of SHAQ, and three collections of iSHORT with SHAQ. Data collection is ongoing. SUMMARY A novel assessment suite has been developed to further aid the comparison and complementary understanding of the habitability and human factors measures, which will allow for efficient deployment of these measures in analogs and/or spaceflight in near-term research as well as support well-being and performance through design.

J C W Miller↗

DOE OSTI2020

Materials Data on HfSi2 by Materials Project

HfSi2 is Zirconium Disilicide structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Hf is bonded in a 10-coordinate geometry to ten Si atoms. There are a spread of Hf–Si bond distances ranging from 2.70–2.96 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 8-coordinate geometry to six equivalent Hf and two equivalent Si atoms. Both Si–Si bond lengths are 2.42 Å. In the second Si site, Si is bonded in a 8-coordinate geometry to four equivalent Hf and four equivalent Si atoms. All Si–Si bond lengths are 2.60 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on HfGa3 by Materials Project

HfGa3 is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Hf is bonded to twelve Ga atoms to form HfGa12 cuboctahedra that share corners with four equivalent HfGa12 cuboctahedra, edges with eight equivalent HfGa12 cuboctahedra, edges with sixteen equivalent GaHf4Ga8 cuboctahedra, faces with four equivalent HfGa12 cuboctahedra, and faces with eight equivalent GaHf4Ga8 cuboctahedra. There are four shorter (2.76 Å) and eight longer (3.00 Å) Hf–Ga bond lengths. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded in a square co-planar geometry to four equivalent Hf and eight equivalent Ga atoms. All Ga–Ga bond lengths are 3.00 Å. In the second Ga site, Ga is bonded to four equivalent Hf and eight Ga atoms to form distorted GaHf4Ga8 cuboctahedra that share corners with twelve equivalent GaHf4Ga8 cuboctahedra, edges with eight equivalent HfGa12 cuboctahedra, edges with eight equivalent GaHf4Ga8 cuboctahedra, faces with four equivalent HfGa12 cuboctahedra, and faces with ten equivalent GaHf4Ga8 cuboctahedra. All Ga–Ga bond lengths are 2.76 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on HfGa2 by Materials Project

HfGa2 crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. Hf is bonded in a 10-coordinate geometry to ten Ga atoms. There are a spread of Hf–Ga bond distances ranging from 2.80–3.00 Å. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded in a distorted square co-planar geometry to four equivalent Hf and four equivalent Ga atoms. There are two shorter (3.03 Å) and two longer (3.06 Å) Ga–Ga bond lengths. In the second Ga site, Ga is bonded in a 12-coordinate geometry to six equivalent Hf and six Ga atoms. Both Ga–Ga bond lengths are 2.77 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Hf2Ga3 by Materials Project

Hf2Ga3 crystallizes in the orthorhombic Fdd2 space group. The structure is three-dimensional. Hf is bonded in a 7-coordinate geometry to nine Ga atoms. There are a spread of Hf–Ga bond distances ranging from 2.79–3.16 Å. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded in a 10-coordinate geometry to six equivalent Hf and four equivalent Ga atoms. There are two shorter (2.62 Å) and two longer (2.72 Å) Ga–Ga bond lengths. In the second Ga site, Ga is bonded in a 10-coordinate geometry to six equivalent Hf and four Ga atoms. Both Ga–Ga bond lengths are 2.75 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on HfGe2 by Materials Project

HfGe2 is Zirconium Disilicide structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Hf is bonded in a 10-coordinate geometry to ten Ge atoms. There are a spread of Hf–Ge bond distances ranging from 2.78–3.13 Å. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 4-coordinate geometry to six equivalent Hf and two equivalent Ge atoms. Both Ge–Ge bond lengths are 2.63 Å. In the second Ge site, Ge is bonded in a 8-coordinate geometry to four equivalent Hf and four equivalent Ge atoms. All Ge–Ge bond lengths are 2.70 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on HfRe2 by Materials Project

HfRe2 is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Hf is bonded in a 12-coordinate geometry to twelve Re atoms. There are three shorter (3.08 Å) and nine longer (3.10 Å) Hf–Re bond lengths. There are two inequivalent Re sites. In the first Re site, Re is bonded to six equivalent Hf and six equivalent Re atoms to form a mixture of face, edge, and corner-sharing ReHf6Re6 cuboctahedra. All Re–Re bond lengths are 2.67 Å. In the second Re site, Re is bonded to six equivalent Hf and six Re atoms to form a mixture of face, edge, and corner-sharing ReHf6Re6 cuboctahedra. There are two shorter (2.56 Å) and two longer (2.72 Å) Re–Re bond lengths.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on HfAl3 by Materials Project

Al3Hf is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Hf is bonded to twelve Al atoms to form HfAl12 cuboctahedra that share corners with four equivalent HfAl12 cuboctahedra, edges with eight equivalent HfAl12 cuboctahedra, edges with sixteen equivalent AlHf4Al8 cuboctahedra, faces with four equivalent HfAl12 cuboctahedra, and faces with eight equivalent AlHf4Al8 cuboctahedra. There are four shorter (2.79 Å) and eight longer (2.98 Å) Hf–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a distorted square co-planar geometry to four equivalent Hf and eight equivalent Al atoms. All Al–Al bond lengths are 2.98 Å. In the second Al site, Al is bonded to four equivalent Hf and eight Al atoms to form AlHf4Al8 cuboctahedra that share corners with twelve equivalent AlHf4Al8 cuboctahedra, edges with eight equivalent HfAl12 cuboctahedra, edges with eight equivalent AlHf4Al8 cuboctahedra, faces with four equivalent HfAl12 cuboctahedra, and faces with ten equivalent AlHf4Al8 cuboctahedra. All Al–Al bond lengths are 2.79 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on KHfH2OF5 by Materials Project

KHfH2OF5 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 10-coordinate geometry to ten F1- atoms. There are a spread of K–F bond distances ranging from 2.70–3.34 Å. In the second K1+ site, K1+ is bonded in a 8-coordinate geometry to one O2- and seven F1- atoms. The K–O bond length is 2.92 Å. There are a spread of K–F bond distances ranging from 2.67–2.85 Å. There are two inequivalent Hf4+ sites. In the first Hf4+ site, Hf4+ is bonded in a 8-coordinate geometry to one O2- and seven F1- atoms. The Hf–O bond length is 2.30 Å. There are a spread of Hf–F bond distances ranging from 2.00–2.34 Å. In the second Hf4+ site, Hf4+ is bonded in a 8-coordinate geometry to one O2- and seven F1- atoms. The Hf–O bond length is 2.30 Å. There are a spread of Hf–F bond distances ranging from 2.01–2.31 Å. There are four 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 0.98 Å. In the second H1+ site, H1+ is bonded in a distorted linear geometry to one O2- and one F1- atom. The H–O bond length is 1.00 Å. The H–F bond length is 1.59 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 distorted single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted water-like geometry to one K1+, one Hf4+, and two H1+ atoms. In the second O2- site, O2- is bonded in a distorted water-like geometry to one Hf4+ and two H1+ atoms. There are ten inequivalent F1- sites. In the first F1- site, F1- is bonded in a 1-coordinate geometry to two K1+ and one Hf4+ atom. In the second F1- site, F1- is bonded in a 1-coordinate geometry to two equivalent K1+ and one Hf4+ atom. In the third F1- site, F1- is bonded in a 1-coordinate geometry to two K1+ and one Hf4+ atom. In the fourth F1- site, F1- is bonded in a 2-coordinate geometry to two K1+ and two Hf4+ atoms. In the fifth F1- site, F1- is bonded in a linear geometry to one K1+ and two Hf4+ atoms. In the sixth F1- site, F1- is bonded in a 3-coordinate geometry to two equivalent K1+, one Hf4+, and one H1+ atom. In the seventh F1- site, F1- is bonded in a 1-coordinate geometry to two equivalent K1+ and one Hf4+ atom. In the eighth F1- site, F1- is bonded in a 2-coordinate geometry to one K1+ and two Hf4+ atoms. In the ninth F1- site, F1- is bonded in a 1-coordinate geometry to two K1+ and one Hf4+ atom. In the tenth F1- site, F1- is bonded in a 1-coordinate geometry to one K1+ and two Hf4+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Hf2Al3C4 by Materials Project

Hf2Al3C4 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Hf is bonded to six C atoms to form HfC6 octahedra that share corners with three equivalent HfC6 octahedra, corners with three equivalent AlC4 tetrahedra, edges with nine equivalent HfC6 octahedra, and edges with three equivalent AlC4 tetrahedra. The corner-sharing octahedral tilt angles are 0°. There are three shorter (2.31 Å) and three longer (2.46 Å) Hf–C bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded to four C atoms to form AlC4 tetrahedra that share corners with three equivalent HfC6 octahedra, corners with seven equivalent AlC4 tetrahedra, and edges with three equivalent HfC6 octahedra. The corner-sharing octahedral tilt angles are 18°. There are one shorter (2.03 Å) and three longer (2.05 Å) Al–C bond lengths. In the second Al site, Al is bonded in a trigonal planar geometry to three equivalent C atoms. All Al–C bond lengths are 1.93 Å. There are three inequivalent C sites. In the first C site, C is bonded to three equivalent Hf and three equivalent Al atoms to form distorted CHf3Al3 octahedra that share corners with three equivalent CHf6 octahedra, corners with three equivalent CAl5 trigonal bipyramids, and edges with nine CHf3Al3 octahedra. The corner-sharing octahedral tilt angles are 5°. In the second C site, C is bonded to five Al atoms to form CAl5 trigonal bipyramids that share corners with six equivalent CHf3Al3 octahedra and corners with six equivalent CAl5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 70°. In the third C site, C is bonded to six equivalent Hf atoms to form a mixture of edge and corner-sharing CHf6 octahedra. The corner-sharing octahedral tilt angles are 5°.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on HfNi5 by Materials Project

HfNi5 crystallizes in the cubic F-43m space group. The structure is three-dimensional. Hf is bonded in a 12-coordinate geometry to sixteen Ni atoms. There are twelve shorter (2.76 Å) and four longer (2.88 Å) Hf–Ni bond lengths. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded to three equivalent Hf and nine Ni atoms to form a mixture of distorted face, edge, and corner-sharing NiHf3Ni9 cuboctahedra. There are a spread of Ni–Ni bond distances ranging from 2.34–2.76 Å. In the second Ni site, Ni is bonded in a 4-coordinate geometry to four equivalent Hf and twelve equivalent Ni atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Hf2N2O by Materials Project

Hf2ON2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Hf4+ sites. In the first Hf4+ site, Hf4+ is bonded in a 8-coordinate geometry to six N3- and two equivalent O2- atoms. There are a spread of Hf–N bond distances ranging from 2.17–2.32 Å. There are one shorter (2.45 Å) and one longer (2.60 Å) Hf–O bond lengths. In the second Hf4+ site, Hf4+ is bonded to four N3- and three equivalent O2- atoms to form distorted edge-sharing HfN4O3 pentagonal bipyramids. There are a spread of Hf–N bond distances ranging from 2.16–2.26 Å. There are two shorter (2.15 Å) and one longer (2.44 Å) Hf–O bond lengths. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded to five Hf4+ atoms to form a mixture of distorted corner, edge, and face-sharing NHf5 square pyramids. In the second N3- site, N3- is bonded to five Hf4+ atoms to form a mixture of distorted corner, edge, and face-sharing NHf5 square pyramids. O2- is bonded in a 2-coordinate geometry to five Hf4+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on HfTiO4 by Materials Project

HfTiO4 is Hydrophilite-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Hf4+ sites. In the first Hf4+ site, Hf4+ is bonded to six O2- atoms to form HfO6 octahedra that share corners with two equivalent TiO6 octahedra, corners with six HfO6 octahedra, and edges with two TiO6 octahedra. The corner-sharing octahedra tilt angles range from 50–58°. There are a spread of Hf–O bond distances ranging from 2.03–2.15 Å. In the second Hf4+ site, Hf4+ is bonded to six O2- atoms to form HfO6 octahedra that share corners with four equivalent HfO6 octahedra, corners with four TiO6 octahedra, an edgeedge with one HfO6 octahedra, and an edgeedge with one TiO6 octahedra. The corner-sharing octahedra tilt angles range from 50–58°. There are a spread of Hf–O bond distances ranging from 2.04–2.15 Å. In the third Hf4+ site, Hf4+ is bonded to six O2- atoms to form distorted HfO6 octahedra that share corners with two equivalent HfO6 octahedra, corners with six TiO6 octahedra, and edges with two HfO6 octahedra. The corner-sharing octahedra tilt angles range from 48–56°. There are a spread of Hf–O bond distances ranging from 2.02–2.22 Å. In the fourth Hf4+ site, Hf4+ is bonded to six O2- atoms to form distorted HfO6 octahedra that share corners with eight TiO6 octahedra, an edgeedge with one HfO6 octahedra, and an edgeedge with one TiO6 octahedra. The corner-sharing octahedra tilt angles range from 48–56°. There are a spread of Hf–O bond distances ranging from 2.03–2.20 Å. There are four inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to six O2- atoms to form distorted TiO6 octahedra that share corners with four HfO6 octahedra, corners with four equivalent TiO6 octahedra, an edgeedge with one HfO6 octahedra, and an edgeedge with one TiO6 octahedra. The corner-sharing octahedra tilt angles range from 47–54°. There are a spread of Ti–O bond distances ranging from 1.87–2.21 Å. In the second Ti4+ site, Ti4+ is bonded to six O2- atoms to form distorted TiO6 octahedra that share corners with two equivalent TiO6 octahedra, corners with six HfO6 octahedra, and edges with two TiO6 octahedra. The corner-sharing octahedra tilt angles range from 48–56°. There are a spread of Ti–O bond distances ranging from 1.91–2.13 Å. In the third Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with eight HfO6 octahedra, an edgeedge with one HfO6 octahedra, and an edgeedge with one TiO6 octahedra. The corner-sharing octahedra tilt angles range from 48–55°. There are a spread of Ti–O bond distances ranging from 1.90–2.13 Å. In the fourth Ti4+ site, Ti4+ is bonded to six O2- atoms to form distorted TiO6 octahedra that share corners with two equivalent HfO6 octahedra, corners with six TiO6 octahedra, and edges with two HfO6 octahedra. The corner-sharing octahedra tilt angles range from 47–55°. There are a spread of Ti–O bond distances ranging from 1.88–2.24 Å. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Hf4+ and two Ti4+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Hf4+ and two Ti4+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two Hf4+ and one Ti4+ atom. In the fourth O2- site, O2- is bonded in a trigonal planar geometry to one Hf4+ and two Ti4+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Hf4+ and two Ti4+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Hf4+ and two Ti4+ atoms. In the seventh O2- site, O2- is bonded in a trigonal planar geometry to three Hf4+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Hf4+ and one Ti4+ atom. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Hf4+ and two Ti4+ atoms. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Hf4+ and one Ti4+ atom. In the eleventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two Hf4+ and one Ti4+ atom. In the twelfth O2- site, O2- is bonded in a trigonal planar geometry to two Hf4+ and one Ti4+ atom. In the thirteenth O2- site, O2- is bonded in a trigonal planar geometry to two Hf4+ and one Ti4+ atom. In the fourteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Hf4+ and two Ti4+ atoms. In the fifteenth O2- site, O2- is bonded in a trigonal planar geometry to two Hf4+ and one Ti4+ atom. In the sixteenth O2- site, O2- is bonded in a 3-coordinate geometry to three Ti4+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Hf2N2O by Materials Project

Hf2ON2 is Ilmenite-like structured and crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. there are two inequivalent Hf4+ sites. In the first Hf4+ site, Hf4+ is bonded to three N3- and three equivalent O2- atoms to form a mixture of distorted face, edge, and corner-sharing HfN3O3 octahedra. The corner-sharing octahedra tilt angles range from 47–63°. There are a spread of Hf–N bond distances ranging from 2.06–2.23 Å. There are a spread of Hf–O bond distances ranging from 2.12–2.31 Å. In the second Hf4+ site, Hf4+ is bonded to five N3- and one O2- atom to form distorted HfN5O octahedra that share corners with nine HfN3O3 octahedra, edges with three HfN3O3 octahedra, and a faceface with one HfN5O octahedra. The corner-sharing octahedra tilt angles range from 47–63°. There are a spread of Hf–N bond distances ranging from 2.10–2.29 Å. The Hf–O bond length is 2.17 Å. There are three inequivalent N3- sites. In the first N3- site, N3- is bonded to four Hf4+ atoms to form distorted NHf4 trigonal pyramids that share corners with four equivalent OHf4 trigonal pyramids, corners with eight NHf4 trigonal pyramids, an edgeedge with one OHf4 trigonal pyramid, and edges with three NHf4 trigonal pyramids. In the second N3- site, N3- is bonded to four Hf4+ atoms to form distorted NHf4 trigonal pyramids that share corners with four equivalent OHf4 trigonal pyramids, corners with eight equivalent NHf4 trigonal pyramids, edges with two equivalent NHf4 trigonal pyramids, and edges with two equivalent OHf4 trigonal pyramids. In the third N3- site, N3- is bonded to four Hf4+ atoms to form distorted NHf4 trigonal pyramids that share corners with four equivalent NHf4 trigonal pyramids, corners with eight equivalent OHf4 trigonal pyramids, and edges with four NHf4 trigonal pyramids. O2- is bonded to four Hf4+ atoms to form distorted OHf4 trigonal pyramids that share corners with two equivalent OHf4 trigonal pyramids, corners with ten NHf4 trigonal pyramids, edges with two NHf4 trigonal pyramids, and edges with two equivalent OHf4 trigonal pyramids.

36 MATERIALS SCIENCE↗