Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “B(HO)2”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Off-shell pion properties: Electromagnetic form factors and light-front wave functions

The off-shell pion electromagnetic form factors are explored with corresponding off-shell light-front wave functions modeled by constituent quark and antiquark. We apply the Mandelstam approach for the microscopic computation of the form factors relating the model parameters with the pion decay constant and charge radius. Analyzing the existing data on the cross sections for the Sullivan process, 1 H(e,e',π + )⁢n, Charged pion form factor between Q 2 = 0.60, and 2.45 GeV 2 . I. Measurements of the cross section for the 1 H⁡(e,e'⁢π + )⁢n reaction, we extract the off-shell pion form factor using the relation derived from the generalized Ward-Takahashi identity for the pion electromagnetic current. They are compared with our previous results from exactly solvable manifestly covariant model of a (3+1)-dimensional fermion field theory. We find that the adopted constituent quark model reproduces the extracted off-shell form factor F 1 ⁡(Q 2 ,t) from the experimental data within a few percent difference and matches well with our previous theoretical simulation which exhibits a variation of about 10% for the extracted off-shell pion form factor g(Q 2 ,t). We also identify the pion valence parton distribution function (PDF) and transverse momentum distribution (TMD) in terms of the light-front wave function and discuss their off-shell properties.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS2024

Offset-Stoichiometric Reflowable Composite Bonding Method with Adhesive for Mitigating Strict Faying Surface Tolerances

Inherent susceptibility of adhesive bonds to miniscule quantities of contamination can cause undetectable weakened bonds. For this reason, the Federal Aviation Administration (FAA) places strict regulations on adhesively bonded joints in primary aircraft structures. To meet certification requirements aircraft manufactures resort to redundant load paths in the form of fasteners which inherently add weight to the structure and increase manufacturing time. In prior work, a secondary bonding technique called AERoBOND was developed, which utilized off-stoichiometric epoxymatrix resins to facilitate reflow and diffusion of the resin within the joint interface during a secondary bonding/cure process, thus achieving a bond similar to a co-cured joint. However, the AERoBOND process required tight spatial tolerances between the two parts being joined. This study examined the utilization of conventional adhesive with the AERoBOND method to act as a filler in the joint line, effectively reducing the need for tight tolerances on the joining parts and serving as a flexible alternative for existing manufacturing processes. Ultrasonic inspection, optical microscopy, and ASTM International standard tests were performed to analyze the joints for defects and to quantify the mode-I and mode-II interlaminar fracture toughness and short beam strength of the proposed methodology with varying manufacturing parameters. The comprehensive results indicate that the AERoBOND+ method with and without surface preparation performs comparably to co-cured and conventional, adhesively bonded joints when secondary cured in an autoclave with 791 kPa of pressure. As an example, the AERoBOND+ panel without surface preparation bonded with 791 kPa of pressure (referred to as AB+3 throughout paper) had a mode-I fracture toughness (G Ic ) of 0.643 kJ/m 2 and a mode-II fracture toughness (G IIc ) of 4.000 kJ/m 2 in the non-precracked condition and 4.218 kJ/m 2 in the precracked condition at the adhesive-to-prepreg interface. These results were 96%, 142%, and 217%, respectively, of a co-cured baseline panel (referred to as C1 throughout paper).

Composites↗
DOE OSTI2020

Templated epitaxy of TiO 2 (B) on a perovskite

The bronze-phase TiO 2 (B) has an open atomic framework that makes it a good candidate for applications in photochemical and electrochemical conversion of energy. However, the synthesis of bronze-phase TiO 2 (B) thin films on perovskite substrates, such as SrTiO 3 (STO), which is one of the most conventional versatile substrates for oxide epitaxy, has been extremely challenging owing to the preferential formation of the anatase TiO 2 over TiO 2 (B). The main reason is that the anatase TiO 2 has not only a smaller lattice mismatch than TiO 2 (B), but also a better structural symmetry match when grown on STO. Here, we demonstrate a way to circumventing this problem by using a VO 2 (B) buffer layer, yielding the growth of a high-quality single crystalline TiO 2 (B) film on a (001)-oriented STO substrate. Finally, from the resulting TiO 2 (B) film, we found that this film has a large optical bandgap of ~3.6 eV, which is close to the known theoretical value, the largest among TiO 2 polymorphs, and useful for developing high-power energy devices.

36 MATERIALS SCIENCE↗
DOE OSTI2023

In Situ High-Temperature Structural Analysis of High-Entropy Rare-Earth Sesquioxides

High-entropy rare-earth (RE) sesquioxides (RE 2 O 3 ) containing five cations in equimolar amounts have been investigated for a variety of applications, but little is known about their polymorphic behavior and coefficient of thermal expansion. Here, in this work, we evaluate the effect of the average ionic radius (AIR) on the polymorphism of high-entropy RE 2 O 3 . Powder samples of compositions 1 (Lu,Y,Ho,Nd,La) 2 O 3 (AIR = 0.938 Å) and 2 (Gd,Eu,Sm,Nd,La) 2 O 3 (AIR = 0.982 Å) were synthesized via a wet chemical method, and bead samples were prepared for aerodynamic levitation by melting the powders in a copper hearth. Structural transitions were monitored upon cooling from the melt to 1000 °C via in situ X-ray diffraction on aerodynamically levitated samples. The phase evolution was liquid, hexagonal H-type, and monoclinic B-type for composition 1 and liquid, cubic X-type, H-type, and B-type for composition 2. Based on their AIR, the general polymorphic transformations of the high-entropy RE 2 O 3 follow the trend of single-RE RE 2 O 3 , but the transition temperatures differ from those of single-RE RE 2 O 3 . The coefficient of thermal expansion values of the B-type phase of compositions 1 and 2 are similar to those of Gd 2 O 3 and previously published high-entropy RE 2 O 3 .

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

Materials Data on HoB7Mo3 by Materials Project

HoMo3B7 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ho3+ is bonded in a 12-coordinate geometry to thirteen B+1.29- atoms. There are a spread of Ho–B bond distances ranging from 2.68–3.34 Å. There are three inequivalent Mo2+ sites. In the first Mo2+ site, Mo2+ is bonded to twelve B+1.29- atoms to form face-sharing MoB12 cuboctahedra. There are a spread of Mo–B bond distances ranging from 2.37–2.49 Å. In the second Mo2+ site, Mo2+ is bonded in a 9-coordinate geometry to nine B+1.29- atoms. There are a spread of Mo–B bond distances ranging from 2.24–2.33 Å. In the third Mo2+ site, Mo2+ is bonded in a 9-coordinate geometry to nine B+1.29- atoms. There are a spread of Mo–B bond distances ranging from 2.24–2.35 Å. There are seven inequivalent B+1.29- sites. In the first B+1.29- site, B+1.29- is bonded in a 9-coordinate geometry to one Ho3+, five Mo2+, and three B+1.29- atoms. There is two shorter (1.81 Å) and one longer (1.85 Å) B–B bond length. In the second B+1.29- site, B+1.29- is bonded in a 2-coordinate geometry to two equivalent Ho3+, five Mo2+, and two equivalent B+1.29- atoms. Both B–B bond lengths are 1.80 Å. In the third B+1.29- site, B+1.29- is bonded in a 3-coordinate geometry to three equivalent Ho3+, three equivalent Mo2+, and three B+1.29- atoms. There is one shorter (1.76 Å) and two longer (1.82 Å) B–B bond length. In the fourth B+1.29- site, B+1.29- is bonded in a 3-coordinate geometry to one Ho3+, five Mo2+, and three B+1.29- atoms. Both B–B bond lengths are 1.79 Å. In the fifth B+1.29- site, B+1.29- is bonded in a 3-coordinate geometry to two equivalent Ho3+, four Mo2+, and three B+1.29- atoms. The B–B bond length is 1.77 Å. In the sixth B+1.29- site, B+1.29- is bonded in a 3-coordinate geometry to two equivalent Ho3+, four Mo2+, and three B+1.29- atoms. In the seventh B+1.29- site, B+1.29- is bonded in a 9-coordinate geometry to two equivalent Ho3+, four Mo2+, and three B+1.29- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Mechanoadaptive strain and functional osseointegration of dental implants in rats

Spatiotemporal implant-bone biomechanics and mechanoadaptive strains in peri-implant tissue are poorly understood. Physical and chemical characteristics of an implant-bone complex (IBC) were correlated in three-dimensional space (along the length and around a dental implant) to gather insights into time related integration of the implant with the cortical portion of a jaw bone in a rat. Rats (N = 9) were divided into three experimental groups with three rats per time point; 3-, 11-, and 24-day. All rats were fed crumbled hard pellets mixed with water (soft-food diet) for the first 3 days followed by a hard-food diet with intact hard-food pellets (groups of 11- and 24-day only). Biomechanics of the IBCs harvested from rats at each time point was evaluated by performing mechanical testing in situ in tandem with X-ray imaging. The effect of physical association (contact area) of a loaded implant with adapting peri-implant tissue, and resulting strain within was mapped by using digital volume correlation (DVC) technique. The IBC stiffness at respective time points was correlated with mechanical strain in peri-implant tissue. Results illustrated that IBC stiffness at 11-day was lower than that observed at 3-day. However, at 24-day, IBC stiffness recovered to that which was observed at 3-day. Furthermore, correlative microscopy and spectroscopy illustrated that the lower IBC stiffness was constituted by softer and less mineralized peri-implant tissue that contained varying expressions of osteoconductive elements. Lower IBC stiffness observed at 11-day was constituted by less mineralized peri-implant tissue with osteoconductive elements that included phosphorus (P) which was co-localized with higher expression of zinc (Zn), and lower expression of calcium (Ca). Higher IBC stiffness at 24-day was constituted by mineralized peri-implant tissue with higher expressions of osteoconductive elements including Ca and P, and lower expressions of Zn. These spatiotemporal correlative maps of peri-implant tissue architecture, heterogeneous distribution of mineral density, and elemental colocalization underscore mechanoadaptive physicochemical properties of peri-implant tissue that facilitate functional osseointegration of an implant. These results provided insights into 1) plausible "prescription" of mechanical loads as an osteoinductive "therapeutic dose" to encourage osteoconductive elements in the peri-implant tissue that would facilitate functional osseointegration of the implant; 2) a "critical temporal window" between 3 and 11 days, and perhaps it is this acute phase during which key candidate regenerative molecules can be harnessed to accelerate osseointegration of an implant under load.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Chemistry and P-V-T equation of state of FeO 2 H x at the base of Earth’s lower mantle and their geophysical implications

The hydrogen-absorbing ability of a mantle mineral in its structure determines the capacity of the water reservoirs hosted by the mineral. Water reservoirs at the base of Earth’s mantle directly influence the fate of water brought down by slab subduction and the seismic heterogeneity such as ultralow-velocity zones (ULVZs) at the core-mantle boundary. Pyrite-FeO 2 H x (0 ≤ x ≤ 1) presents a possibility of such reservoirs in the deep mantle. Ever since the discovery of this mineral phase, however, its chemistry at the lower mantle conditions has been debated. We conducted kinetics experiments of pyrite-FeO 2 H x dehydrogenation at 110 GPa/2100 K, 110 GPa/2300 K, and 120 GPa/2300 K and P-V-T equation of state analysis using in situ synchrotron X-ray diffraction. We found that x approaches 0.80, 0.75, and 0.79, respectively, at the above conditions. The collective P-V-T data yield K 0 = 241(13) GPa, K' = 4.2(4), dK/dT = –0.028(1) GPa/K, α 0 = 4.32(13) × 10 –5 K –1 , and α 1 = 0.31(10) × 10 –8 K –2 for the composition of x = 0.75 ± 0.04. Our first-principles calculations indicate that FeO 2 H 0.75 with a slightly distorted pyrite structure is stable at 100 GPa. These results indicate that this mineral is likely present in the deep mantle with rather a partially dehydrogenated composition than FeO 2 or FeOOH. Furthermore, the results also clarify the difference between the ULVZs originated from pyrite-FeO 2 H x and those from partial melting in terms of shear and compressional wave seismic velocity reduction ratio δlnV S /δlnV P .

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

Mineralogy of the deep lower mantle in the presence of H 2 O

Understanding the mineralogy of the Earth's interior is a prerequisite for unravelling the evolution and dynamics of our planet. Here, we conducted high pressure-temperature experiments mimicking the conditions of the deep lower mantle (DLM, 1800–2890 km in depth) and observed surprising mineralogical transformations in the presence of water. Ferropericlase, (Mg, Fe)O, which is the most abundant oxide mineral in Earth, reacts with H 2 O to form a previously unknown (Mg, Fe)O 2 H x (x ≤ 1) phase. The (Mg, Fe)O 2 H x has a pyrite structure and it coexists with the dominant silicate phases, bridgmanite and post-perovskite. Depending on Mg content and geotherm temperatures, the transformation may occur at 1800 km for (Mg 0.6 Fe 0.4 )O or beyond 2300 km for (Mg 0.7 Fe 0.3 )O. The (Mg, Fe)O 2 H x is an oxygen excess phase that stores an excessive amount of oxygen beyond the charge balance of maximum cation valences (Mg 2+ , Fe 3+ and H + ). This important phase has a number of far-reaching implications including extreme redox inhomogeneity, deep-oxygen reservoirs in the DLM and an internal source for modulating oxygen in the atmosphere.

58 GEOSCIENCES↗
NASA NTRS2012

Metasomatic Control of Water in Garnet and Pyroxene from Kaapvaal Craton Mantle Xenoliths

Fourier transform infrared spectrometry (FTIR) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) were used to determine water, rare earth (REE), lithophile (LILE), and high field strength (HFSE) element contents in garnet and pyroxene from mantle xenoliths, Kaapvaal craton, southern Africa. Water enters these nominally anhydrous minerals as protons bonded to structural oxygen in lattice defects. Pyroxene water contents (150-400 ppm in clinopyroxene; 40-250 ppm in orthopyroxene) correlate with their Al, Fe, Ca and Na and are homogeneous within a mineral grains and a xenolith. Garnets from Jagersfontein are chemically zoned for Cr, Ca, Ti and water contents. Garnets contain 0 to 20 ppm H2 Despite the fast diffusion rate of H in mantle m inerals, the observations above indicate that the water contents of mantle xenolith minerals were not disturbed during kimberlite entrainment and that the measured water data represent mantle values. Trace elements in all minerals show various degrees of light REE and LILE enrichments indicative of minimal to strong metasomatism. Water contents of peridotite minerals from the Kaapvaal lithosphere are not related to the degree of depletion of the peridotites. Instead, metasomatism exerts a clear control on the amount of water of mantle minerals. Xenoliths from each location record specific types of metasomatism with different outcomes for the water contents of mantle minerals. At pressures . 5.5 GPa, highly alkaline melts metasomatized Liqhobong and Kimberley peridotites, and increased the water contents of their olivine, pyroxenes and garnet. At higher pressures, the circulation of ultramafic melts reacting with peridotite resulted in co-variation of Ca, Ti and water at the edge of garnets at Jagersfontein, overall decreasing their water content, and lowered the water content of olivines at Finsch Mine. The calculated water content of these melts varies depending on whether the water content of the peridotite (2 wt% HO. 2O) or individual m inerals (<0.5-13 wt% H2O) are used, and also depend on the mineral-melt water partition coefficients. These metasomatic events are thought to have occurred during the Archean and Proterozoic, meaning that the water contents measured here have been preserved since that time and can be used to investigate viscocity and longevity of cratonic mantle roots.

Peslier, Anne H.↗
DOE OSTI2020

Materials Data on HoCo(BO2)5 by Materials Project

HoCo(BO2)5 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ho3+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ho–O bond distances ranging from 2.25–2.92 Å. Co2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Co–O bond distances ranging from 2.06–2.43 Å. There are five inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.37 Å) and two longer (1.38 Å) B–O bond length. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.35–1.40 Å. In the third B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.47–1.51 Å. In the fourth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.47–1.50 Å. In the fifth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.47–1.50 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one Ho3+, two equivalent Co2+, and one B3+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+, one Co2+, and two B3+ atoms. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one Ho3+ and two B3+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and two B3+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ho3+ and two B3+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Co2+ and two B3+ atoms. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one Ho3+, one Co2+, and two B3+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Co2+ and two B3+ atoms. In the ninth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and two B3+ atoms. In the tenth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ho3+ and one B3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Resonant and bound states of charged defects in two-dimensional semiconductors

A detailed understanding of charged defects in two-dimensional semiconductors is needed for the development of ultrathin electronic devices. Here, we study negatively charged acceptor impurities in monolayer WS 2 using a combination of scanning tunnelling spectroscopy and large-scale atomistic electronic structure calculations. We observe several localized defect states of hydrogenic wave function character in the vicinity of the valence band edge. Some of these defect states are bound, while others are resonant. The resonant states result from the multi-valley valence band structure of WS$_2$, whereby localized states originating from the secondary valence band maximum at Γ hybridize with continuum states from the primary valence band maximum at K/K$^{\prime}$. Resonant states have important consequences for electron transport as they can trap mobile carriers for several tens of picoseconds.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

High-resolution laser-induced fluorescence spectroscopy of 28 Si 16 O + and 29 Si 16 O + in a cryogenic buffer-gas cell

Here, the electronic, laser-induced fluorescence spectrum of the B 2 Σ + ← X 2 Σ + transition in 28 Si 16 O + and 29 Si 16 O + has been recorded in a cryogenic buffer gas cell at K. Molecular constants are extracted for both 28 Si 16 O + and 29 Si 16 O + , including the Fermi contact hyperfine constant for both the B and X states of 29 Si 16 O + , and used in a discussion of the suitability of SiO in future quantum information experiments.

47 OTHER INSTRUMENTATION↗
NASA NTRS1994

The relationship between interplanetary discontinuities and Alfven waves: Ulysses observations

The rate of occurrence of interplanetary discontinuities (ROID) is examined using Ulysses magnetic field and plasma data from 1 to 5 AU radial distance from the Sun and at high heliographic latitudes. We find two regions where the ROID is high: in stream-stream interaction regions and in Alfven wave trains. This latter feature is particularly obvious at high latitudes when Ulysses enters a high speed stream associated with a polar coronal hole. These streams are characterized by the presence of continuous, large-amplitude (Delta (vector 13)/absolute value of B is about 1-2 Alfven waves and an extraordinarily high ROID value (approximately 150 discontinuities/day). In a number of intervals examined, it is found that (rotational) discontinuities are an integral part of the Alfven waves. The nonlinear Alfven waves are spherically polarized, i.e., the tip of the perturbation vector resides on the surface of a sphere (a consequence of constant absolute value of B). The slowly rotating part of the wave rotates approximately 270 deg in phase. There is a slight arc in the B(sub 1) - B(sub 2) hodogram, suggesting an almost linear polarization. The phase rotation associated with the discontinuity is about 90 deg, lies in the same plane as the slowly rotaing part of the Alfven wave, and therefore completes the 360 deg phase rotation. The best description of the overall Alfven wave plus discontinuity is a spherical, arc-polarized, phase-steepened wave.

Tsurutani, B. T.↗
DOE OSTI2021

Structural, Vibrational, and Electronic Properties of 1D-TlInTe 2 under High Pressure: A Combined Experimental and Theoretical Study

Analogous to 2D layered transition-metal dichalcogenides, the TlSe family of quasi-one dimensional chain materials with the Zintl-type structure exhibits novel phenomena under high pressure. In the present work, we have systematically investigated the high-pressure behavior of TlInTe 2 using Raman spectroscopy, synchrotron X-ray diffraction (XRD), and transport measurements, in combination with first principles crystal structure prediction (CSP) based on evolutionary approach. We found that TlInTe2 undergoes a pressure-induced semiconductor-to-semimetal transition at 4 GPa, followed by a superconducting transition at 5.7 GPa (with T c = 3.8 K). An unusual giant phonon mode (A g ) softening appears at ~10–12 GPa as a result of the interaction of optical phonons with the conduction electrons. The high-pressure XRD and Raman spectroscopy studies reveal that there is no structural phase transitions observed up to the maximum pressure achieved (33.5 GPa), which is in agreement with our CSP calculations. In addition, our calculations predict two high-pressure phases above 35 GPa following the phase transition sequence as I4/mcm (B37) → Pbcm → Pm$\bar{3}$m (B2). Electronic structure calculations suggest Lifshitz (L1 & L2-type) transitions near the superconducting transition pressure. Furthermore, our findings on TlInTe 2 open up a new avenue to study unexplored high-pressure novel phenomena in TlSe family induced by Lifshitz transition (electronic driven), giant phonon softening, and electron–phonon coupling.

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

Composition and Dynamical Processes of Ions in Giant Magnetospheres: The Importance of In Situ Measurements for Advancing the Current Knowledge [Slides]

In this white paper, we emphasize the importance of in situ ion composition measurements provided by plasma mass spectrometers in planetary magnetospheres (Uranus and Neptune) aimed for future planetary missions. We present our current understanding on magnetospheres of Uranus and Neptune that are largely based on Plasma Science Investigation (PLS, faraday cups) and Low Energy Charged Particle (LECP) instrument on Voyager 2 and what measurements need to be made to improve it. We emphasize that the future missions equipped with plasma mass spectrometers must visit these magnetospheres again to advance our current knowledge. Finally, this white paper summarizes key science questions that needs to be addressed which all of them requires a direct ion composition measurements from a plasma spectrometer.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Materials Data on Ho2B4O9 by Materials Project

Ho2B4O9 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are five inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ho–O bond distances ranging from 2.27–2.69 Å. In the second Ho3+ site, Ho3+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ho–O bond distances ranging from 2.26–2.86 Å. In the third Ho3+ site, Ho3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ho–O bond distances ranging from 2.29–2.81 Å. In the fourth Ho3+ site, Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.22–2.78 Å. In the fifth Ho3+ site, Ho3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ho–O bond distances ranging from 2.25–2.73 Å. There are ten inequivalent B3+ sites. In the first B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.49–1.52 Å. In the second B3+ site, B3+ is bonded to four O2- atoms to form a mixture of edge and corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.44–1.51 Å. In the third B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.40–1.59 Å. In the fourth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.43–1.54 Å. In the fifth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.46–1.50 Å. In the sixth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.42–1.52 Å. In the seventh B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.45–1.50 Å. In the eighth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.43–1.52 Å. In the ninth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.44–1.52 Å. In the tenth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.45–1.51 Å. There are twenty-three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ho3+ and two B3+ atoms. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ho3+ and two B3+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Ho3+ and two equivalent B3+ atoms. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ho3+ and two B3+ atoms. In the sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ho3+ and two B3+ atoms. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ho3+ and two B3+ atoms. In the ninth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ho3+ and two B3+ atoms. In the tenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and two equivalent B3+ atoms. In the eleventh O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the twelfth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ho3+ and two B3+ atoms. In the thirteenth O2- site, O2- is bonded in a 2-coordinate geometry to one Ho3+ and two B3+ atoms. In the fourteenth O2- site, O2- is bonded in a 2-coordinate geometry to two Ho3+ and two B3+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ho3+ and two equivalent B3+ atoms. In the sixteenth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ho3+ and two B3+ atoms. In the seventeenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ho3+ and two B3+ atoms. In the eighteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ho3+ and two B3+ atoms. In the nineteenth O2- site, O2- is bonded in a distorted single-bond geometry to two Ho3+ and one B3+ atom. In the twentieth O2- site, O2- is bonded in a 2-coordinate geometry to two Ho3+ and two B3+ atoms. In the twenty-first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ho3+ and two B3+ atoms. In the twenty-second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ho3+ and two B3+ atoms. In the twenty-third O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Circulating SARS-CoV-2 spike N439K variants maintain fitness while evading antibody-mediated immunity

SARS-CoV-2 can mutate and evade immunity, with consequences for efficacy of emerging vaccines and antibody therapeutics. Here, we demonstrate that the immunodominant SARS-CoV-2 spike (S) receptor binding motif (RBM) is a highly variable region of S and provide epidemiological, clinical, and molecular characterization of a prevalent, sentinel RBM mutation, N439K. We demonstrate N439K S protein has enhanced binding affinity to the hACE2 receptor, and N439K viruses have similar in vitro replication fitness and cause infections with similar clinical outcomes as compared to wild type. We show the N439K mutation confers resistance against several neutralizing monoclonal antibodies, including one authorized for emergency use by the US Food and Drug Administration (FDA), and reduces the activity of some polyclonal sera from persons recovered from infection. Immune evasion mutations that maintain virulence and fitness such as N439K can emerge within SARS-CoV-2 S, highlighting the need for ongoing molecular surveillance to guide development and usage of vaccines and therapeutics.

60 APPLIED LIFE SCIENCES↗