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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on MoSCl7O by Materials Project

MoOCl4SCl3 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four MoOCl4 clusters and four SCl3 clusters. In each MoOCl4 cluster, Mo3+ is bonded in a 1-coordinate geometry to one O2- and four Cl1- atoms. The Mo–O bond length is 1.70 Å. There are a spread of Mo–Cl bond distances ranging from 2.34–2.47 Å. O2- is bonded in a single-bond geometry to one Mo3+ atom. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 1-coordinate geometry to one Mo3+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Mo3+ atom. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one Mo3+ atom. In the fourth Cl1- site, Cl1- is bonded in a single-bond geometry to one Mo3+ atom. In each SCl3 cluster, S6+ is bonded in a trigonal non-coplanar geometry to three Cl1- atoms. There are one shorter (2.01 Å) and two longer (2.03 Å) S–Cl bond lengths. There are three inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one S6+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one S6+ atom. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one S6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Au3N3(Cl6O)2 by Materials Project

AuCl4Au2N(OCl4)2N2 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of eight ammonia molecules, four Au2N(OCl4)2 clusters, and four AuCl4 clusters. In each Au2N(OCl4)2 cluster, Au3+ is bonded in a rectangular see-saw-like geometry to four Cl1- atoms. There are a spread of Au–Cl bond distances ranging from 2.30–2.43 Å. N+2.33+ is bonded in a linear geometry to two equivalent Cl1- atoms. Both N–Cl bond lengths are 2.08 Å. O2- is bonded in a single-bond geometry to one Cl1- atom. The O–Cl bond length is 1.53 Å. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a distorted bent 120 degrees geometry to one Au3+ and one N+2.33+ atom. In the second Cl1- site, Cl1- is bonded in a distorted bent 120 degrees geometry to one Au3+ and one O2- atom. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one Au3+ atom. In the fourth Cl1- site, Cl1- is bonded in a single-bond geometry to one Au3+ atom. In each AuCl4 cluster, Au3+ is bonded in a square co-planar geometry to four Cl1- atoms. There are two shorter (2.30 Å) and two longer (2.31 Å) Au–Cl bond lengths. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one Au3+ atom. In the second Cl1- site, Cl1- is bonded in a distorted single-bond geometry to one Au3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoH22N7(ClO2)4 by Materials Project

(CoN3H6O4Cl)2(NH4)2(N3H12Cl)2(ClO4)2Cl2 crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two ammonium molecules, two hydrochloric acid molecules, two ClO4 clusters, two CoN3H6O4Cl clusters, and two N3H12Cl clusters. In each ClO4 cluster, there are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Cl1- atom. The O–Cl bond length is 1.46 Å. In the second O2- site, O2- is bonded in a single-bond geometry to one Cl1- atom. The O–Cl bond length is 1.47 Å. In the third O2- site, O2- is bonded in a single-bond geometry to one Cl1- atom. The O–Cl bond length is 1.47 Å. Cl1- is bonded in a tetrahedral geometry to four O2- atoms. In each CoN3H6O4Cl cluster, Co3+ is bonded to three N+0.71- and one O2- atom to form CoN3O tetrahedra that share a cornercorner with one ClO4 tetrahedra. There is one shorter (1.85 Å) and two longer (1.94 Å) Co–N bond length. The Co–O bond length is 2.03 Å. There are two inequivalent N+0.71- sites. In the first N+0.71- site, N+0.71- is bonded in a distorted trigonal planar geometry to one Co3+ and two equivalent H1+ atoms. Both N–H bond lengths are 1.03 Å. In the second N+0.71- site, N+0.71- is bonded in a distorted trigonal non-coplanar geometry to one Co3+ and two H1+ atoms. Both N–H bond lengths are 1.03 Å. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N+0.71- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N+0.71- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N+0.71- atom. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Cl1- atom. The O–Cl bond length is 1.46 Å. In the second O2- site, O2- is bonded in a single-bond geometry to one Cl1- atom. The O–Cl bond length is 1.47 Å. In the third O2- site, O2- is bonded in a linear geometry to one Co3+ and one Cl1- atom. The O–Cl bond length is 1.46 Å. Cl1- is bonded to four O2- atoms to form ClO4 tetrahedra that share a cornercorner with one CoN3O tetrahedra. In each N3H12Cl cluster, there are two inequivalent N+0.71- sites. In the first N+0.71- site, N+0.71- is bonded in a tetrahedral geometry to four H1+ atoms. There are a spread of N–H bond distances ranging from 1.03–1.06 Å. In the second N+0.71- site, N+0.71- is bonded in a tetrahedral geometry to four H1+ atoms. There is three shorter (1.03 Å) and one longer (1.06 Å) N–H bond length. There are seven inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N+0.71- and one Cl1- atom. The H–Cl bond length is 2.00 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N+0.71- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N+0.71- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one N+0.71- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one N+0.71- and one Cl1- atom. The H–Cl bond length is 1.97 Å. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one N+0.71- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one N+0.71- atom. Cl1- is bonded in a 3-coordinate geometry to three H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A Sodium–Antimony–Telluride Intermetallic Allows Sodium-Metal Cycling at 100% Depth of Discharge and as an Anode-Free Metal Battery

In this work, repeated cold rolling and folding is employed to fabricate a metallurgical composite of sodium–antimony–telluride Na 2 (Sb 2/6 Te 3/6 Vac 1/6 ) dispersed in electrochemically active sodium metal, termed “NST-Na.” This new intermetallic has a vacancy-rich thermodynamically stable face-centered-cubic structure and enables state-of-the-art electrochemical performance in widely employed carbonate and ether electrolytes. NST-Na achieves 100% depth-of-discharge (DOD) in 1 m NaPF 6 in G2, with 15 mAh cm –2 at 1 mA cm –2 and Coulombic efficiency (CE) of 99.4%, for 1000 h of plating/stripping. Sodium-metal batteries (SMBs) with NST-Na and Na 3 V 2 (PO 4 ) 3 (NVP) or sulfur cathodes give significantly improved energy, cycling, and CE (>99%). An anode-free battery with NST collector and NVP obtains 0.23% capacity decay per cycle. Imaging and tomography using conventional and cryogenic microscopy (Cryo-EM) indicate that the sodium metal fills the open space inside the self-supporting sodiophilic NST skeleton, resulting in dense (pore-free and solid electrolyte interphase (SEI)-free) metal deposits with flat surfaces. The baseline Na deposit consists of filament-like dendrites and “dead metal”, intermixed with pores and SEI. Density functional theory calculations show that the uniqueness of NST lies in the thermodynamic stability of the Na atoms (rather than clusters) on its surface that leads to planar wetting, and in its own stability that prevents decomposition during cycling.

36 MATERIALS SCIENCE↗
DOE OSTI2026

A kinetic model for simulating non-equilibrium mass transport in oxides applied to hematite growth under irradiation

We propose an approach to simulating the dynamic evolution and transport of charged point defects within and through the oxide scales that form during corrosion. The method follows the cluster dynamics formalism widely adopted for radiation damage in solids, which can apply in both quasi-static and far from equilibrium conditions, such as in radiation environments. By treating each charged defect as a cluster of an atomic defect and associated unit charges, the proposed model flexibly allows charge state transitions and shifts in the Fermi level by absorption and emission of charge carriers from point defects in a reaction network with rates constrained by local equilibrium. Applying this model to hematite predicts changes in self-diffusion and oxidation kinetics in irradiation environments, surprisingly showing reduced oxidation rates in many conditions, despite enhanced self-diffusion. In conclusion, the origin of this effect lies in a change in Fermi level induced by excess vacancies formed under irradiation, which in turn suppresses the transport of cation interstitials which facilitate hematite growth.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Behavior of helium cavities in ion-irradiated W-Ni-Fe ductile-phase toughened tungsten

This study reports on the distribution of helium (He) cavities in a hot-rolled W-Ni-Fe ductile-phase toughened tungsten (DPT W) composite irradiated to a dose and a helium concentration that are comparable to those in the material after 5-year irradiation in a conceptual fusion power plant. Here, the DPT W sample consists of W particles embedded in a ductile-phase NiFeW matrix with a nominal composition of 90W-7Ni-3Fe by weight. It was hot-rolled to a thickness reduction by 87% (87R DPT W). Sequential irradiation of the material with 1.2 MeV Ni + ions to a fluence of 2.15×10 16 Ni + /cm 2 and 90 keV He + ions to 6.5×10 15 He + /cm 2 was performed at 973 K. Larger He cavities with a lower number density are observed in NiFeW than W. Helium cavities are aggregated preferentially along the NiFeW/W interphase boundary. This behavior is not observed along the W/W grain boundary under the same irradiation conditions. A similar distribution of He cavities with comparable sizes is observed in 87R DPT W irradiated with He + ions only, suggesting that the He cavity distribution is not significantly affected by pre-irradiation of Ni + ions at 973 K. The data from this study does not provide any evidence for formation of visible voids or Ni precipitates in W phase irradiated with Ni + ions only. Diffusion and clustering of He atoms and mobile vacancies during ion irradiation at 973 K are responsible for the formation and growth of the He cavities.

36 MATERIALS SCIENCE↗
DOE OSTI2020

MoS 2 -supported Au 31 for CO hydrogenation: A first-principle study

While the basal plane of single-layer molybdenum disulphide (MoS 2 ) is inert, attempts have been made to functionalize it chemically through the creation of defects and/or addition of dopants. With nanoparticles as dopants, the authors present density functional theory-based calculations of the hydrogenation of CO on a 31-atom, bilayer Au cluster supported on single-layer MoS 2 (Au31/MoS 2 ). Not surprisingly, the adsorption and reaction of all species involved in the hydrogenation occur at the edges of the cluster—the regions at which the interaction between MoS 2 and the Au cluster is tracked to be the strongest. The authors find two possible mechanisms that lead to the formation of methanol: (1) CO* → CHO* → CH 2 O* → CH 3 O* → CH 3 OH* and (2) CO* → CHO* → HCOH* → CH2OH* → CH3OH*, where * indicates the adsorbed species. Detailed analysis of the reaction pathways, however, does not result in favoring one mechanism over the other. Rather, both mechanisms are facile. In addition, the rate-limiting step in each mechanism is found to be the formation of the formyl radical group (CO* + H* → CHO*).

2D materials↗
DOE OSTI2023

Multielectronic and multiatomic effects in the U O 4,5 x-ray absorption spectroscopy of uranium dioxide

In order to explain all of the spectral features observed in the U O 4,5 x-ray absorption spectrum of uranium dioxide (UO 2 ), it is necessary to include both multielectron effects and multiatomic effects. The 5d (core hole)-5f (electron) angular momentum coupling that gives rise to the giant resonance has been treated within ligand field density functional theory, and the electron scattering that generates the extended x-ray absorption fine structure has been included via the spectral simulation program FEFF: both within a UO 8 fluorite cluster picture. An atomic model is insufficient to explain all of the observed spectral features.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SICl7 by Materials Project

SCl3ICl4 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four ICl4 clusters and four SCl3 clusters. In each ICl4 cluster, I5+ is bonded in a rectangular see-saw-like geometry to four Cl1- atoms. There are a spread of I–Cl bond distances ranging from 2.47–2.61 Å. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one I5+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one I5+ atom. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one I5+ atom. In the fourth Cl1- site, Cl1- is bonded in a single-bond geometry to one I5+ atom. In each SCl3 cluster, S2+ is bonded in a distorted trigonal non-coplanar geometry to three Cl1- atoms. All S–Cl bond lengths are 2.03 Å. There are three inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one S2+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one S2+ atom. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one S2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on OsXe(O2F3)2 by Materials Project

XeOF4OsO3F2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of one OsO3F2 cluster and two XeOF4 clusters. In the OsO3F2 cluster, Os is bonded in a 6-coordinate geometry to three O and three F atoms. All Os–O bond lengths are 1.71 Å. There are a spread of Os–F bond distances ranging from 1.96–2.16 Å. There are three inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Os atom. In the second O site, O is bonded in a single-bond geometry to one Os atom. In the third O site, O is bonded in a single-bond geometry to one Os atom. There are two inequivalent F sites. In the first F site, F is bonded in a water-like geometry to two equivalent Os atoms. In the second F site, F is bonded in a single-bond geometry to one Os atom. In each XeOF4 cluster, Xe is bonded in a square pyramidal geometry to one O and four F atoms. The Xe–O bond length is 1.83 Å. There are two shorter (2.03 Å) and two longer (2.04 Å) Xe–F bond lengths. O is bonded in a single-bond geometry to one Xe atom. There are four inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one Xe atom. In the second F site, F is bonded in a single-bond geometry to one Xe atom. In the third F site, F is bonded in a single-bond geometry to one Xe atom. In the fourth F site, F is bonded in a single-bond geometry to one Xe atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MoSe2Cl4O by Materials Project

MoOCl4MoSeOCl4(Se)3 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of twelve selenium molecules, four MoOCl4 clusters, and two MoSeOCl4 clusters. In each MoOCl4 cluster, Mo4+ is bonded in a 1-coordinate geometry to one O2- and four Cl1- atoms. The Mo–O bond length is 1.69 Å. There are a spread of Mo–Cl bond distances ranging from 2.38–2.42 Å. O2- is bonded in a single-bond geometry to one Mo4+ atom. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one Mo4+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Mo4+ atom. In the third Cl1- site, Cl1- is bonded in a distorted single-bond geometry to one Mo4+ atom. In the fourth Cl1- site, Cl1- is bonded in a distorted single-bond geometry to one Mo4+ atom. In each MoSeOCl4 cluster, Mo4+ is bonded in a 1-coordinate geometry to one O2- and five Cl1- atoms. The Mo–O bond length is 1.70 Å. There are a spread of Mo–Cl bond distances ranging from 2.34–3.00 Å. Se1+ is bonded in a distorted single-bond geometry to one Cl1- atom. The Se–Cl bond length is 2.95 Å. O2- is bonded in a single-bond geometry to one Mo4+ atom. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one Mo4+ atom. In the second Cl1- site, Cl1- is bonded in a distorted water-like geometry to two equivalent Mo4+ atoms. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one Mo4+ atom. In the fourth Cl1- site, Cl1- is bonded in a distorted single-bond geometry to one Mo4+ and one Se1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MoCl5O by Materials Project

MoOCl5 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four hydrochloric acid molecules, four MoOCl4 clusters, and four MoOCl5 clusters. In each MoOCl4 cluster, Mo is bonded in a 5-coordinate geometry to one O and four Cl atoms. The Mo–O bond length is 1.69 Å. There are a spread of Mo–Cl bond distances ranging from 2.29–2.36 Å. O is bonded in a single-bond geometry to one Mo atom. There are four inequivalent Cl sites. In the first Cl site, Cl is bonded in a single-bond geometry to one Mo atom. In the second Cl site, Cl is bonded in a single-bond geometry to one Mo atom. In the third Cl site, Cl is bonded in a single-bond geometry to one Mo atom. In the fourth Cl site, Cl is bonded in a single-bond geometry to one Mo atom. In each MoOCl5 cluster, Mo is bonded in a 5-coordinate geometry to one O and four Cl atoms. The Mo–O bond length is 1.69 Å. There are a spread of Mo–Cl bond distances ranging from 2.30–2.37 Å. O is bonded in a single-bond geometry to one Mo atom. There are five inequivalent Cl sites. In the first Cl site, Cl is bonded in a single-bond geometry to one Mo atom. In the second Cl site, Cl is bonded in a single-bond geometry to one Cl atom. The Cl–Cl bond length is 2.46 Å. In the third Cl site, Cl is bonded in a single-bond geometry to one Mo atom. In the fourth Cl site, Cl is bonded in a single-bond geometry to one Mo atom. In the fifth Cl site, Cl is bonded in a distorted single-bond geometry to one Mo and one Cl atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PtRhBr6N5Cl by Materials Project

(Pt)2RhN5Br5ClRhN5Br3Cl(Br)4 crystallizes in the monoclinic P2_1/m space group. The structure is zero-dimensional and consists of eight hydrobromic acid molecules, four platinum molecules, two RhN5Br3Cl clusters, and two RhN5Br5Cl clusters. In each RhN5Br3Cl cluster, Rh4+ is bonded in a distorted octahedral geometry to five N3- and one Cl1- atom. There are a spread of Rh–N bond distances ranging from 1.88–2.08 Å. The Rh–Cl bond length is 2.45 Å. There are three inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted L-shaped geometry to one Rh4+ and one Br1+ atom. The N–Br bond length is 1.81 Å. In the second N3- site, N3- is bonded in a distorted L-shaped geometry to one Rh4+ and one Br1+ atom. The N–Br bond length is 1.89 Å. In the third N3- site, N3- is bonded in a distorted bent 120 degrees geometry to one Rh4+ and one Br1+ atom. The N–Br bond length is 1.82 Å. There are three inequivalent Br1+ sites. In the first Br1+ site, Br1+ is bonded in an L-shaped geometry to two equivalent N3- atoms. In the second Br1+ site, Br1+ is bonded in a single-bond geometry to one N3- atom. In the third Br1+ site, Br1+ is bonded in an L-shaped geometry to two equivalent N3- atoms. Cl1- is bonded in a distorted single-bond geometry to one Rh4+ atom. In each RhN5Br5Cl cluster, Rh4+ is bonded in a distorted octahedral geometry to five N3- and one Cl1- atom. There are a spread of Rh–N bond distances ranging from 1.84–2.26 Å. The Rh–Cl bond length is 2.45 Å. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted trigonal non-coplanar geometry to one Rh4+ and two equivalent Br1+ atoms. Both N–Br bond lengths are 1.97 Å. In the second N3- site, N3- is bonded in a distorted trigonal non-coplanar geometry to one Rh4+ and two equivalent Br1+ atoms. Both N–Br bond lengths are 1.95 Å. In the third N3- site, N3- is bonded in a distorted single-bond geometry to one Rh4+ and one Br1+ atom. The N–Br bond length is 2.33 Å. In the fourth N3- site, N3- is bonded in a distorted single-bond geometry to one Rh4+ and one Br1+ atom. The N–Br bond length is 1.96 Å. There are three inequivalent Br1+ sites. In the first Br1+ site, Br1+ is bonded in a single-bond geometry to one N3- atom. In the second Br1+ site, Br1+ is bonded in a single-bond geometry to one N3- atom. In the third Br1+ site, Br1+ is bonded in a 1-coordinate geometry to two N3- atoms. Cl1- is bonded in a single-bond geometry to one Rh4+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1974

Solar wind and micrometeorite alteration of the lunar regolith

Developments in the understanding of reduction processes which occur in the lunar regolith as a result of solar-wind bombardment and micrometeorite impacts are discussed. The mechanism is described by which water released during reduction is removed from the lunar surface, and the possible contribution of solar-wind sputtering to the reduction process is considered. It is shown that the overall reduction efficiency of incoming hydrogen ions may reach several per cent, which is sufficient to produce all the metallic iron observed in the regolith. Mossbauer spectroscopic data on the amount of metallic iron present as isolated atoms or small clusters in reduced grain surfaces are presented together with data on the metallic iron content of fines samples obtained by Mossbauer spectroscopy, ferromagnetic resonance, and scanning as well as transmission electron microscopy. A portable magnetic probe is described which has been designed for determining surface-exposure age profiles in intact lunar core and drive-tube samples.

Housley, R. M.↗
NASA NTRS1989

Radiation damage in scientific charge-coupled devices

Radiation damage is reported on CCDs (charge-coupled devices) that have been primarily exposed to 1.25-MeV gamma rays (Co-60 source). Two important classes of radiation damage are discussed, namely, bulk and ionization effects. Bulk damage or displacement damage is a process in which silicon atoms are displaced from their normal lattice positions by high-energy photons or particles. Single atomic displacements or cluster defect damage is produced, depending on the energy and type of radiation experienced by the detector. Bulk damage creates trapping sites within the CCD's signal channel which in turn degrades charge-transfer efficiency.

Janesick, James↗
NASA NTRS1999

Low-Energy Sputtering Studies of Boron Nitride with Xenon Ions

Sputtering of boron nitride with xenon ions was investigated using secondary ion (SIMS) and secondary neutral (SNMS) mass spectrometry. The ions generated from the ion gun were incident on the target at an angle of 50' with respect to the surface'normal. The energy of ions ranged from 100 eV to 3 keV. A flood electron gun was used to neutralize the positive charge build-up on the target surface. The intensities of sputtered neutral and charged particles, including single atoms, molecules, and clusters, were measured as a function of ion energy. Positive SIMS spectra were dominated by the two boron isotopes whereas BN- and B- were the two major constituents of the negative SIMS spectra. Nitrogen could be detected only in the SNMS spectra. The intensity-energy curves of the sputtered particles were similar in shape. The knees in P-SIMS and SNMS intensity-energy curves appear at around I keV which is significantly higher that 100 to 200 eV energy range at which knees appear in the sputtering of medium and heavy elements by ions of argon and xenon. This difference in the position of the sputter yield knee between boron nitride and heavier targets is due to the reduced ion energy differences. The isotopic composition of secondary ions of boron were measured by bombarding boron nitride with xenon ions at energies ranging from 100 eV to 1.5 keV using a quadrupole mass spectrometer. An ion gun was used to generate the ion beam. A flood electron gun was used to neutralize the positive charge buildup on the target surface. The secondary ion flux was found to be enriched in heavy isotopes at lower incident ion energies. The heavy isotope enrichment was observed to decrease with increasing primary ion energy. Beyond 350 eV, light isotopes were sputtered preferentially with the enrichment increasing to an asymptotic value of 1.27 at 1.5 keV. The trend is similar to that of the isotopic enrichment observed earlier when copper was sputtered with xenon ions in the same energy range.

Ray, P. K.↗
NASA NTRS2001

NATO Advanced Study Institute on Spectroscopy

This booklet presents an account of the course 'Spectroscopy of Systems with Spatially Confined Structures' held in Erice-Sicily, Italy, from June 15 to June 30, 2001. This meeting was organized by the International School of Atomic and Molecular Spectroscopy of the 'Ettore Majorana' Centre for Scientific Culture. The purpose of this course was to present and discuss nanometer-scale physics, a rapidly progressing field. The top-down approach of semiconductor technology will soon meet the scales of the bottom-up approaches of supramolecular chemistry and of spatially localized excitations in ionic crystals. This course dealt with the fabrication, measurement and understanding of the relevant structures and brought together the scientific communities responsible for these development. The advances in this area of physics have already let to applications in optoelectronics and will likely lead to many more. The subjects of the course included spatially resolved structures such as quantum wells, quantum wires and quantum dots, single atoms and molecules, clusters, fractal systems, and the development of related techniques like near-field spectroscopy and confocal microscopy to study such systems.

DiBartolo, Baldassare↗
NASA NTRS2022

Diffusion in Melts and Magmas

Diffusion results from random motion of particles and entities. Diffusion in melts and magmas is due to thermally excited random motion of atoms, ions, and clusters, and plays a critical role in magmatic and volcanic processes. In melts and magmas, diffusion is one of the two mechanisms of mass transfer; the other being bulk flow (referred to as convection or advection). When both are present, diffusion refers to the dispersive motion relative to the mean bulk flow in a given reference frame (Richter et al. 1998). Diffusion plays critical roles in controlling magma mixing (Watson 1982; Koyaguchi 1985, 1989; Lesher 1994; Huber et al. 2009; Guo and Zhang 2020), mineral growth and dissolution rates in magmas (e.g., Watson 1982; Harrison and Watson 1983; Zhang et al. 1989; Newcombe et al. 2014; Macris et al. 2018), bubble growth and dissolution rate in magmas (Sparks 1978; Proussevitch and Sahagian 1998; Liu and Zhang 2000; Zhang 2013), and elemental and isotope fractionation during mineral 2 growth and dissolution (Jambon 1980; Richter et al. 1999, 2003; Watson and Muller 2009; Chopra et al. 2012; Watkins et al. 2014, 2017; Holycross et al. 2016, 2018). As a result, diffusion also plays an essential role in explosive volcanic eruptions and magma crystallization. Furthermore, diffusion has important applications in geospeedometry (Lasaga 1983, 1998; Zhang 1994, 2008; Trail et al. 2016; Zhang and Xu 2016). Experimental investigation of diffusion in geologically relevant silicate melts began to flourish in the 1970’s when micro-analytical measurements of diffusion profiles became available. In addition to the vast number of papers published since then, numerous books and reviews are available for diffusion in silicate melts. Hofmann et al. (1974) edited a book titled “Geochemical Transport and Kinetics” published by Carnegie Institution of Washington. This was the first landmark book summarizing the field. Lasaga and Kirkpatrick (1981) edited a book “Kinetics of Geochemical Processes” as volume 8 of the Reviews in Mineralogy (later becoming Reviews in Mineralogy and Geochemistry) series. Zhang and Cherniak (2010) edited “Diffusion in Minerals and Melts” as volume 72 of Reviews of Mineralogy and Geochemistry series, in which one chapter focused on diffusion theory, five chapters on diffusion in silicate melts (Behrens 2010; Lesher 2010; Liang 2010; Zhang and Ni 2010; Zhang et al. 2010), and other chapters were on experimental, analytical, and computational methods, and diffusion in minerals. Several textbooks covered the principles and applications of diffusion theories (Kirkaldy and Young 1987; Shewmon 1989; Cussler 1997; Lasaga 1998; Zhang 2008; Vrentas and Vrentas 2016), and two classic books covered the mathematics of diffusion (Carslaw and Jaeger 1959; Crank 1975). In preparing for this review chapter, we thought carefully about what to cover for this vast field, and decided to briefly go through the fundamentals of diffusion (more complete review can be found in Chakraborty 1995; Zhang 2008, 2010) and solutions to often-encountered 3 diffusion problems, and then focus on post-2010 diffusion studies on silicate melts and magmas. Here, melts refer to (mostly natural) silicate liquid, and magmas refer to crystal-bearing and/or bubble-bearing melts in which the continuous phase is the melt. There is a large body of work on diffusion in glasses, especially in the materials science literature, which is not covered in this review.

Youxue Zhang↗