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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on IrOs by Materials Project

OsIr is Magnesium-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Os is bonded to six equivalent Os and six equivalent Ir atoms to form OsIr6Os6 cuboctahedra that share corners with eighteen equivalent OsIr6Os6 cuboctahedra, edges with six equivalent OsIr6Os6 cuboctahedra, edges with twelve equivalent IrIr6Os6 cuboctahedra, faces with eight equivalent OsIr6Os6 cuboctahedra, and faces with twelve equivalent IrIr6Os6 cuboctahedra. All Os–Os bond lengths are 2.76 Å. All Os–Ir bond lengths are 2.71 Å. Ir is bonded to six equivalent Os and six equivalent Ir atoms to form IrIr6Os6 cuboctahedra that share corners with eighteen equivalent IrIr6Os6 cuboctahedra, edges with six equivalent IrIr6Os6 cuboctahedra, edges with twelve equivalent OsIr6Os6 cuboctahedra, faces with eight equivalent IrIr6Os6 cuboctahedra, and faces with twelve equivalent OsIr6Os6 cuboctahedra. All Ir–Ir bond lengths are 2.76 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LaGe3Os by Materials Project

LaOsGe3 crystallizes in the tetragonal I4mm space group. The structure is three-dimensional. La is bonded in a 12-coordinate geometry to five equivalent Os and twelve Ge atoms. There are one shorter (3.49 Å) and four longer (3.54 Å) La–Os bond lengths. There are a spread of La–Ge bond distances ranging from 3.26–3.47 Å. Os is bonded in a 5-coordinate geometry to five equivalent La and five Ge atoms. There are one shorter (2.39 Å) and four longer (2.47 Å) Os–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 1-coordinate geometry to four equivalent La, one Os, and four equivalent Ge atoms. All Ge–Ge bond lengths are 2.79 Å. In the second Ge site, Ge is bonded in a 2-coordinate geometry to four equivalent La, two equivalent Os, and two equivalent Ge atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbBOs by Materials Project

NbOsB crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are three inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded in a 11-coordinate geometry to six Os2- and five B3- atoms. There are a spread of Nb–Os bond distances ranging from 2.77–2.88 Å. There are a spread of Nb–B bond distances ranging from 2.35–2.71 Å. In the second Nb5+ site, Nb5+ is bonded in a 10-coordinate geometry to four Os2- and six B3- atoms. There are two shorter (2.76 Å) and two longer (2.77 Å) Nb–Os bond lengths. There are a spread of Nb–B bond distances ranging from 2.34–2.40 Å. In the third Nb5+ site, Nb5+ is bonded in a 2-coordinate geometry to eight Os2- and four B3- atoms. There are a spread of Nb–Os bond distances ranging from 2.80–2.92 Å. There are a spread of Nb–B bond distances ranging from 2.44–2.77 Å. There are three inequivalent Os2- sites. In the first Os2- site, Os2- is bonded in a 2-coordinate geometry to six Nb5+ and three B3- atoms. There are two shorter (2.24 Å) and one longer (2.58 Å) Os–B bond lengths. In the second Os2- site, Os2- is bonded in a 2-coordinate geometry to six Nb5+ and three B3- atoms. There are two shorter (2.23 Å) and one longer (2.46 Å) Os–B bond lengths. In the third Os2- site, Os2- is bonded in a 9-coordinate geometry to six Nb5+ and three B3- atoms. There are two shorter (2.26 Å) and one longer (2.45 Å) Os–B bond lengths. There are three inequivalent B3- sites. In the first B3- site, B3- is bonded in a 9-coordinate geometry to six Nb5+, one Os2-, and two B3- atoms. There is one shorter (1.89 Å) and one longer (1.95 Å) B–B bond length. In the second B3- site, B3- is bonded in a 9-coordinate geometry to three Nb5+ and six Os2- atoms. In the third B3- site, B3- is bonded in a 9-coordinate geometry to six Nb5+, two Os2-, and one B3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ZnOs3 by Materials Project

Os3Zn is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Os+0.67- is bonded to eight equivalent Os+0.67- and four equivalent Zn2+ atoms to form distorted OsZn4Os8 cuboctahedra that share corners with four equivalent ZnOs12 cuboctahedra, corners with fourteen equivalent OsZn4Os8 cuboctahedra, edges with six equivalent ZnOs12 cuboctahedra, edges with twelve equivalent OsZn4Os8 cuboctahedra, faces with four equivalent ZnOs12 cuboctahedra, and faces with sixteen equivalent OsZn4Os8 cuboctahedra. There are a spread of Os–Os bond distances ranging from 2.67–2.82 Å. There are two shorter (2.67 Å) and two longer (2.75 Å) Os–Zn bond lengths. Zn2+ is bonded to twelve equivalent Os+0.67- atoms to form ZnOs12 cuboctahedra that share corners with six equivalent ZnOs12 cuboctahedra, corners with twelve equivalent OsZn4Os8 cuboctahedra, edges with eighteen equivalent OsZn4Os8 cuboctahedra, faces with eight equivalent ZnOs12 cuboctahedra, and faces with twelve equivalent OsZn4Os8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H2Os3C8(SO4)2 by Materials Project

Os3C8H2(SO4)2 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of four Os3C8H2(SO4)2 clusters. there are two inequivalent Os2- sites. In the first Os2- site, Os2- is bonded to two equivalent C3+, two equivalent H1+, and two equivalent S2- atoms to form distorted face-sharing OsH2C2S2 octahedra. Both Os–C bond lengths are 1.89 Å. Both Os–H bond lengths are 1.76 Å. Both Os–S bond lengths are 2.46 Å. In the second Os2- site, Os2- is bonded to three C3+, one H1+, and two equivalent S2- atoms to form distorted OsHC3S2 octahedra that share an edgeedge with one OsHC3S2 octahedra and a faceface with one OsH2C2S2 octahedra. There are a spread of Os–C bond distances ranging from 1.88–1.93 Å. The Os–H bond length is 2.01 Å. Both Os–S bond lengths are 2.44 Å. There are four inequivalent C3+ sites. In the first C3+ site, C3+ is bonded in a linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.16 Å. In the second C3+ site, C3+ is bonded in a linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.17 Å. In the third C3+ site, C3+ is bonded in a linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C3+ site, C3+ is bonded in a linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.16 Å. H1+ is bonded in an L-shaped geometry to two Os2- atoms. S2- is bonded in a 3-coordinate geometry to three Os2- atoms. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C3+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C3+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C3+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ScGeOs by Materials Project

ScOsGe crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Sc is bonded in a 11-coordinate geometry to six equivalent Os and five Ge atoms. There are two shorter (2.96 Å) and four longer (3.01 Å) Sc–Os bond lengths. There are four shorter (2.75 Å) and one longer (2.81 Å) Sc–Ge bond lengths. Os is bonded in a 10-coordinate geometry to six equivalent Sc and four Ge atoms. There are two shorter (2.49 Å) and two longer (2.64 Å) Os–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to six equivalent Sc and three equivalent Os atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to three equivalent Sc and six equivalent Os atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaOs3 by Materials Project

TaOs3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ta5+ is bonded to twelve equivalent Os+1.67- atoms to form TaOs12 cuboctahedra that share corners with twelve equivalent TaOs12 cuboctahedra, edges with twenty-four equivalent OsTa4Os8 cuboctahedra, faces with six equivalent TaOs12 cuboctahedra, and faces with twelve equivalent OsTa4Os8 cuboctahedra. All Ta–Os bond lengths are 2.78 Å. Os+1.67- is bonded to four equivalent Ta5+ and eight equivalent Os+1.67- atoms to form distorted OsTa4Os8 cuboctahedra that share corners with twelve equivalent OsTa4Os8 cuboctahedra, edges with eight equivalent TaOs12 cuboctahedra, edges with sixteen equivalent OsTa4Os8 cuboctahedra, faces with four equivalent TaOs12 cuboctahedra, and faces with fourteen equivalent OsTa4Os8 cuboctahedra. All Os–Os bond lengths are 2.78 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaOsO9 by Materials Project

BaOsO9 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Ba–O bond distances ranging from 2.74–3.12 Å. Os is bonded in a distorted octahedral geometry to six O atoms. There are a spread of Os–O bond distances ranging from 1.77–2.04 Å. There are six inequivalent O sites. In the first O site, O is bonded in a distorted water-like geometry to one Ba and one O atom. The O–O bond length is 1.29 Å. In the second O site, O is bonded in a bent 120 degrees geometry to two equivalent O atoms. In the third O site, O is bonded in a water-like geometry to one Ba and one Os atom. In the fourth O site, O is bonded in a distorted bent 150 degrees geometry to one Ba and one Os atom. In the fifth O site, O is bonded in a distorted water-like geometry to one Ba and one Os atom. In the sixth O site, O is bonded in a distorted single-bond geometry to two equivalent Ba and one Os atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Microstructural evolution and transmutation in tungsten under ion and neutron irradiation

This study aims to compare the effects of neutron and self-ion irradiation on the mechanical properties and microstructural evolution in W. Neutron irradiation at the HFR reactor to 1.67 dpa at 800 °C resulted in the formation of large Re and Os rich clusters and voids. The post-irradiation composition was measured using APT and verfified against FISPACT modelling. The measured Re and Os concentration was used to create alloys with equivalent concentrations of Re and Os. These alloys were exposed to self-ion irradiation to a peak dose of 1.7 dpa at 800 °C. APT showed that self-ion irradiation leads to the formation of small Os clusters, wheras under neutron irradiation large Re/Os clusters form. Voids are formed by both ion and neutron irradiation, but the voids formed by neutron irradiation are larger. By comparing the behaviour of W-1.4Re and W-1.4Re-0.1Os, suppression of Re cluster formation was observed. Irradiation hardening was measured using nanoindentation and was found to be 2.7 GPa, after neutron irradiation and 1.6 GPa and 0.6 GPa for the self-ion irradiated W-1.4Re and W-1.4Re-0.1Os. The higher hardening is attributed to the barrier strength of large voids and Re/Os clusters that are observed after neutron irradiation.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Locoregional Treatment of Glioblastoma With Targeted α Therapy: [213Bi]Bi-DOTA–Substance P Versus [225Ac]Ac-DOTA–Substance P—Analysis of Influence Parameters

Background Glioblastoma (GB) is the most malignant primary brain tumor. Therefore, introduction of new treatment options is critically important. The aim of this study was to assess local treatment with α emitters [ 213 Bi]Bi-DOTA–substance P (SP) and [ 225 Ac]Ac-DOTA-SP. Methods Treatment was performed as salvage therapy in patients with recurrent primary and secondary GB. [ 213 Bi]Bi-DOTA-SP with injected activity 1.85 GBq per cycle was used in 20 primary (48.2 ± 11.8 years old) and in 9 secondary (38.8 ± 10.8 years old) GB patients and [ 225 Ac]Ac-DOTA-SP in 15 primary (45.1 ± 9.9 years old) and in 6 secondary (37.8 ± 6.4 years old) GB patients with a dose escalation scheme (10, 20, and 30 MBq). Results Local treatment with [ 213 Bi]Bi-DOTA-SP and [ 225 Ac]Ac-DOTA-SP was well tolerated with only few adverse effects. There was no statistically significant difference between [ 213 Bi]Bi-DOTA-SP and [ 225 Ac]Ac-DOTA-SP groups in survival parameters. For primary GB, survival parameters of patients treated with [ 213 Bi]Bi-DOTA-SP and [ 225 Ac]Ac-DOTA-SP were as follows(in months): progression-free survival time, 2.7 versus 2.4; OS-d (overall survival from time of diagnosis to death from any cause), 23.6 versus 21.0; OS-t (overall survival from the start of treatment to death from any cause), 7.5 versus 5.0; and OS-r (overall survival from recurrence in primary tumors to death from any cause), 10.9 versus 12.0. Survival parameters of secondary GB patients treated with [ 213 Bi]Bi-DOTA-SP and [ 225 Ac]Ac-DOTA-SP were as follows (in months): progression-free survival time, 5.8 versus 2.4; OS-d, 52.3 versus 65.0; OS-t, 16.4 versus 16.0; and OS-c (overall survival from conversion into secondary GB multiforme to death from any cause), 18.4 versus 36.0. Conclusions The similarity results of 213 Bi or 225 Ac may suggest that the local treatment of brain tumors can be greatly simplified. The experience to date shows that local radioisotope treatment of brain tumors requires further dosimetry studies, taking into account the complexity of biological processes.

Radiology, Nuclear Medicine & Medical Imaging↗
DOE OSTI2020

Robust Online Sequential RVFLNs for Data Modeling of Dynamic Time-Varying Systems with Application of an Ironmaking Blast Furnace

In a world where the increasing complexity of modern industrial processes brings difficulties for accurate mathematical modeling, taking advantage of data has become an efficient solution to complex dynamic process modeling issue. In this paper, we develop a novel robust online sequential version of random vector functional-link networks (RVFLNs) for data-driven modeling of dynamic time-varying system and applied it in a blast furnace (BF) ironmaking process. First, to overcome the time-varying dynamics of process and to enable the RVFLNs to learn online with avoiding data saturation, an improved online sequential version of RVFLNs (OS-RFVLNs) is first presented by online sequential learning with forgetting factor. This improved OS-RVFLNs algorithm is not only suitable for the real-time and large data transfer situation, but also can adjust the sensitivity of the algorithm to different samples with the help of the introduced forgetting factor. Second, since the output weights of the improved OS-RVFLNs as well as other RVFLNs algorithms are obtained by the least squares approach, a robustness problem may occur when the training dataset is contaminated with various outliers. To solve this problem, a Cauchy distribution weighted M-estimator is introduced to improve the robustness of the improved OS- RVFLNs. For this proposed robust OS-RVFLNs (R-OS- RVFLNs), since the weights of different outlier data are properly determined by the Cauchy distribution function, their corresponding contribution on modeling can be properly distinguished. Thus robust and better modeling results can be achieved. Experiments using actual industrial data of BF ironmaking process and comparative studies have demonstrated that the proposed method produces a better estimation accuracy and stronger robustness than other methods.

Blast furnace (BF), Modelling, Dynamic systems↗
DOE OSTI2023

Acute Ozone-Induced Transcriptional Changes in Markers of Oxidative Stress and Glucocorticoid Signaling in the Rat Hippocampus and Hypothalamus Are Sex-Specific

Exposure to a prototypic air pollutant ozone (O 3 ) has been associated with the activation of neuroendocrine stress response along with neural changes in oxidative stress (OS), inflammation, and Alzheimer’s disease-like pathologies in susceptible animal models. We hypothesized that neural oxidative and transcriptional changes induced by O 3 in stress responsive regions are sex-dependent. Male and female adult Long–Evans rats were exposed to filtered air or O 3 for two consecutive days (0.8 ppm, 4 h/day) and brain regions were flash-frozen. Activities of cerebellar OS parameters and mitochondrial complex I, II, and IV enzymes were assessed to confirm prior findings. We assessed transcriptional changes in hypothalamus (HYP) and hippocampus (HIP) for markers of OS, microglial activity and glucocorticoid signaling using qPCR. Although there were no O 3 or sex-related differences in the cerebellar activities of OS and mitochondrial enzymes, the levels of protein carbonyls and complex II activities were higher in females regardless of O 3 . There were no statistical differences in baseline expression of genes related to OS (Cat, Dhcr24, Foxm1, Gpx1, Gss, Nfe2l2, Sod1) except for lower HYP Sod1 expression in air-exposed females than males, and higher HIP Gss expression in O 3 -exposed females relative to matched males. Microglial marker Aif1 expression was higher in O 3 -exposed females relative to males; O 3 inhibited Itgam only in males. The expression of Bdnf in HIP and HYP was inhibited by O 3 in both sexes. Genes related to glucocorticoid signaling (Fkbp4, Fkbp5, Hsp90aa1, Hspa4, nr3c1, nr3c2) showed sex-specific effects due to O 3 exposure. Baseline expression of HIP Fkbp4 was higher in females relative to males. O 3 inhibited Nr3c1 in female HIP and male HYP, but Nr3c2 was inhibited in male HYP. Fkbp4 expression was higher in O 3 -exposed females when compared to matched males, whereas Fkbp5 was expressed at higher levels in both brain regions of males and females. These results indicate that sex-specific brain region responses to O 3 might, in part, be caused by OS and regulation of glucocorticoid signaling.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1977

Is osmium chemically fractionated in the moon

An investigation was conducted involving the determination of Os in 53 highland samples from the Apollo 14-17 missions. The Os/Ir ratio was found to remain essentially constant at 1.05 as Os and Ir abundances vary over four orders of magnitude. The Os-Au and the Os-Ni correlation in highland samples is presented in graphs. The graphs show that the majority of highland samples have Os/Au and Os/Ni ratios somewhat below the cosmic value. But there is no reason to attribute this trend to a loss of Os by local processes, because two other refractory siderophiles, Ir and Re, show exactly the same trend. Results on more than 150 analyzed highland samples show that meteoritic groups of low (Ir, Re, Os)/Au ratio are much more common at the Apollo landing sites than are groups of high ratio.

Hertogen, J.↗
NASA NTRS1977

Trace element geochemistry and the early lunar differentiation

The results are considered of experiments in which thermal neutron activation analysis was used to measure the halogens, U, Te, Ru, Os, and Hg in lunar samples. A calorimetric method was used for P2O5. Three Apollo 17 basalts, one Apollo 11 basalt, and one Apollo 15 basalt were used for the Ru-Os study. Os and Ru were measured in seven samples of breccia 14305 in a series of experiments to check an apparent anomaly in the isotopic composition of the Hg which it contains. A lunar model for Ru-Os partition is discussed. It is suggested that Ru and Os were partitioned and fractionated in the original differentiation of the lunar surface ocean. Fractionation among near-surface materials was less than a factor of 2 according to the lithic breccia data. Fractionations among basaltic sources were very large, exceeding 100, and primarily due to Ru. A clue to Ru and Os distributions at the depths from which mare basalts were derived may be provided by the relative ages of the basalts. These are interpreted as being related to partial melting in response to temperature increases at depth with time.

Jovanovic, S.↗
NASA NTRS2021

Recommendation on Orbiting Sample Cleanliness

The National Aeronautics and Space Administration-European Space Agency (NASA-ESA) Mars Sample Return (MSR) campaign involves the collection of samples on Mars by the Perseverance (Mars 2020) rover and their return to Earth. To accomplish this, the Orbiting Sample container (OS) will be sent to Mars to accommodate the collected samples then launched from Mars and returned to Earth, where the samples will be removed for examination in the Sample Return Facility (SRF). Crucial to this entire sequence will be establishment of the required level of cleanliness inside the OS. In February 2021, the NASA Headquarters' Mars Sample Return Program and Office of Planetary Protection assembled an MSR OS Tiger Team (OSTT) to discuss the appropriate cleanliness level options of the interior of the OS. The team's remit was primarily focused on evaluating the trade-offs between Planetary Protection cleanliness levels 4a and 4b. These cleanliness levels are determined by the Committee on Space Research (COSPAR) planetary protection regulations, where 4a requires <300 bacterial spores/m^2 and <3 x 10^5 bacterial spores on the spacecraft (in this case, the interior of the OS) and 4b mandates the more stringent requirement of <30 bacterial spores on the spacecraft. This report documents the consensus opinion submitted by the OSTT that recommended the interior of the OS be cleaned to a 4a requirement with any feasible added effort toward 4b. This report provides, as well, the rationale for that decision.

Charles S. Cockell↗
DOE OSTI2020

Materials Data on U2Al3Os by Materials Project

U2OsAl3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. U is bonded in a 3-coordinate geometry to four equivalent U, three equivalent Os, and nine equivalent Al atoms. There are three shorter (3.22 Å) and one longer (3.53 Å) U–U bond lengths. All U–Os bond lengths are 3.12 Å. There are three shorter (3.10 Å) and six longer (3.20 Å) U–Al bond lengths. Os is bonded to six equivalent U and six equivalent Al atoms to form OsU6Al6 cuboctahedra that share corners with twelve equivalent AlU6Al4Os2 cuboctahedra, edges with six equivalent OsU6Al6 cuboctahedra, faces with two equivalent OsU6Al6 cuboctahedra, and faces with eighteen equivalent AlU6Al4Os2 cuboctahedra. All Os–Al bond lengths are 2.70 Å. Al is bonded to six equivalent U, two equivalent Os, and four equivalent Al atoms to form distorted AlU6Al4Os2 cuboctahedra that share corners with four equivalent OsU6Al6 cuboctahedra, corners with fourteen equivalent AlU6Al4Os2 cuboctahedra, edges with six equivalent AlU6Al4Os2 cuboctahedra, faces with six equivalent OsU6Al6 cuboctahedra, and faces with twelve equivalent AlU6Al4Os2 cuboctahedra. There are two shorter (2.65 Å) and two longer (2.69 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sc6Te2Os by Materials Project

Sc6OsTe2 crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. there are two inequivalent Sc sites. In the first Sc site, Sc is bonded in a 4-coordinate geometry to two equivalent Os and two equivalent Te atoms. Both Sc–Os bond lengths are 2.68 Å. Both Sc–Te bond lengths are 3.01 Å. In the second Sc site, Sc is bonded in a 5-coordinate geometry to one Os and four equivalent Te atoms. The Sc–Os bond length is 2.97 Å. All Sc–Te bond lengths are 3.10 Å. Os is bonded in a 9-coordinate geometry to nine Sc atoms. Te is bonded in a 9-coordinate geometry to nine Sc atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy(SiOs)2 by Materials Project

Dy(OsSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Dy3+ is bonded in a 8-coordinate geometry to eight equivalent Os+1.50- atoms. All Dy–Os bond lengths are 3.19 Å. Os+1.50- is bonded in a 4-coordinate geometry to four equivalent Dy3+ and four equivalent Si atoms. All Os–Si bond lengths are 2.40 Å. Si is bonded in a 5-coordinate geometry to four equivalent Os+1.50- and one Si atom. The Si–Si bond length is 2.48 Å.

36 MATERIALS SCIENCE↗