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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Resolving the Atomic Structure of Sequential Infiltration Synthesis Derived Inorganic Clusters

Sequential infiltration synthesis (SIS) is a route to the precision deposition of inorganic solids in analogy to atomic layer deposition but occurs within (vs upon) a soft material template. SIS has enabled exquisite nanoscale morphological complexity in various oxides through selective nucleation in block copolymers templates. However, the earliest stages of SIS growth remain unresolved, including the atomic structure of nuclei and the evolution of local coordination environments, before and after polymer template removal. We employed In K-edge extended X-ray absorption fine structure and atomic pair distribution function analysis of high-energy X-ray scattering to unravel (1) the structural evolution of InO x H y clusters inside a poly(methyl methacrylate) (PMMA) host matrix and (2) the formation of porous In 2 O 3 solids (obtained after annealing) as a function of SIS cycle number. Early SIS cycles result in InO x H y cluster growth with high aspect ratio, followed by the formation of a three-dimensional network with additional SIS cycles. That the atomic structures of the InO x H y clusters can be modeled as multinuclear clusters with bonding patterns related to those in In 2 O 3 and In(OH) 3 crystal structures suggests that SIS may be an efficient route to 3D arrays of discrete-atom-number clusters. As a result, annealing the mixed inorganic/polymer films in air removes the PMMA template and consolidates the as-grown clusters into cubic In 2 O 3 nanocrystals with structural details that also depend on SIS cycle number.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

High-Spin and Reactive Fe 13 Cluster with Exposed Metal Sites

We report atomically defined large metal clusters have applications in new reaction development and preparation of materials with tailored properties. Expanding the synthetic toolbox for reactive high nuclearity metal complexes, we report a new class of Fe clusters, Tp* 4 W 4 Fe 13 S 12 , displaying a Fe 13 core with M-M bonds that has precedent only in main group and late metal chemistry. M 13 clusters with closed shell electron configurations can show significant stability and have been classified as superatoms. In contrast, Tp* 4 W 4 Fe 13 S 12 displays a large spin ground state of S=13. This compound performs small molecule activations involving the transfer of up to 12 electrons resulting in significant cluster rearrangements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Hydrogen Localization and Cluster Formation in α-Zr from First-Principles Investigations

We report alpha-zirconium (α-Zr) is a hydrogen atom host material used in nuclear energy and semiconducting applications due to Zr's excellent properties such as corrosion resistance, low thermal neutrons cross-section, and thermodynamically favorable interstitial sequestering of H atoms. Herein we use density functional theory simulations to systematically analyze the initial stages of H insertion in the Zr matrix, and determine optimal hydrogen localization, distribution, and clustering tendencies from a thermodynamics and kinetics perspective. Our results suggest that H occupation of tetrahedral sites is strongly favored, consistent with previous experimental and theoretical studies. Further, a cooperative effect in H localization is shown where H atoms favor clustering. The H pair is found to be the most stable by occupying tetrahedral sites with pairs at second nearest-neighbor positions (TTn2). Among the four H atom clusters, the most favorable configuration has two TTn2 pairs forming "box " or "zig-zag" shaped-cluster with the pairs separated by 3.03 or 3.25 Å, respectively. Nudged elastic band simulations suggest that the formation of TTn2 is facile and is limited by the small diffusion barrier of the monomer of less than 0.1 eV. Further, the formation routes for the 4H atom clusters are also presented. The current study can serve as a foundation to systematically model H atom clustering in metals and alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Solute clustering in polycrystals: Unveiling the interplay of grain boundary junction and long-range solute attraction effects

Spectral analysis of local atomic environments has become a powerful tool for studying solute atom segregation and interactions at grain boundaries in nanocrystalline alloys. When applied to individual grain boundaries, the spectral analysis has shown that solute-solute interaction can be either attractive or repulsive, with long-range relative attraction enhancing the likelihood for solute atoms to begin clustering. In this article, we combine this analysis with a new grain-boundary structure descriptor based on grain-boundary atom coordination, to investigate the impact of grain-boundary junctions on solute atom segregation in polycrystals. Specifically, we systematically characterize the tendency of solute clusters to begin forming at various types of ordinary grain boundaries, triple junctions, and high-order junctions in Ag polycrystals containing either Ni or Cu solute atoms. Our findings demonstrate that the formation of solute clusters at grain boundaries is primarily driven by long-range relative solute attraction, rather than short-range solute-solute interactions. Furthermore, this effect is most pronounced near grain-boundary junctions. Our study highlights the multiscale nature of solute segregation at crystalline interfaces and provides new insights into the complex phenomena governing heterogeneous solute segregation in grain-boundary networks.

Grain-boundary junction↗
DOE OSTI2022

Helium interaction with solutes and impurities in neutron-irradiated nanostructured ferritic alloys: A first principles study

Density functional theory calculations are performed to explore the binding between He and alloying solutes, impurities, and transmutation products expected in neutron irradiated nanostructured ferritic alloys (NFAs), here 14YWT is taken as an example. Elements that exhibit significant binding (attraction) with an interstitial He are Y (binding energy = 0.46 eV), Mg (0.32), O (0.33), Ti (0.16), and C (0.15). Those that provide significant binding to a substitutional He are O (1.44), Y (1.24), N (0.73), H (0.56), Mg (0.52), Ti (0.34), Si (0.34), C (0.33), Al (0.32), Ni (0.26), Ta (0.23), and Mn (0.16). The presence of these elements in Fe matrix could reduce the transport of He towards oxide particles, dislocations, and internal boundaries, and could promote He bubble nucleation in the matrix. For convenience, we compile existing binding energy data of He with He n and He n V (He-vacancy) clusters. Dissociation pathway analysis reveals that, in general, the most likely dissociation of a He n V cluster is by a sequential emission of individual He atoms. Furthermore, larger bubbles are more prone to dissociation than smaller ones. In addition, we estimate the binding energy (segregation energy) of He in bulk Y 2 Ti 2 O 7 (YTO) single crystal, YTO/Fe interface, and YTO particle embedded in Fe, with respect to interstitial He in Fe, from existing formation energies of He in these structures. We also compile available data of He binding with Fe self-interstitial atom (SIA), SIA clusters, and edge and screw dislocations. Note that given the absence of DFT data, the binding with SIA clusters and dislocations are gathered from simulations with empirical potentials. Finally, the data presented in this paper is important to inform multiscale simulations of He bubble accumulation.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te3As2S(OF6)2 by Materials Project

(Te)3AsTeF6AsTe2F6(AsF6)2(SO2)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of four sulfur dioxide molecules, six tellurium molecules, four AsF6 clusters, two AsTe2F6 clusters, and two AsTeF6 clusters. In each AsF6 cluster, As5+ is bonded in an octahedral geometry to six F1- atoms. There are a spread of As–F bond distances ranging from 1.77–1.79 Å. There are six inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the fifth F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the sixth F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In each AsTe2F6 cluster, As5+ is bonded in an octahedral geometry to six F1- atoms. There are a spread of As–F bond distances ranging from 1.75–1.80 Å. There are two inequivalent Te+2.67+ sites. In the first Te+2.67+ site, Te+2.67+ is bonded in a single-bond geometry to one F1- atom. The Te–F bond length is 2.84 Å. In the second Te+2.67+ site, Te+2.67+ is bonded in a single-bond geometry to one F1- atom. The Te–F bond length is 2.82 Å. There are six inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one As5+ and one Te+2.67+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one As5+ and one Te+2.67+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the fifth F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the sixth F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In each AsTeF6 cluster, As5+ is bonded in an octahedral geometry to six F1- atoms. There are a spread of As–F bond distances ranging from 1.76–1.80 Å. Te+2.67+ is bonded in a distorted single-bond geometry to one F1- atom. The Te–F bond length is 2.86 Å. There are six inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the fifth F1- site, F1- is bonded in a single-bond geometry to one As5+ and one Te+2.67+ atom. In the sixth F1- site, F1- is bonded in a single-bond geometry to one As5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Extended x-ray emission times of clusters in intense x-ray pulses

Novel experimental spectroscopic and imaging techniques have been developed to exploit x-ray free-electron laser (XFEL) for studying structure and dynamic of non-periodic entities at atomic spatial resolution and femtosecond timescales.Recently, intensity correlation of x-ray fluorescence, based on the principle introduced by Hanbury Brown and Twiss [R. Hanbury Brown and R. Q. Twiss, Nature (London) 177, 27 (1956)], has been proposed for high-resolution imaging of a three-dimensional arrangement of atoms. To explore the applicability of this fluorescence approach, we theoretically investigate fluorescence dynamics of nonperiodic systems subject to x-ray free electron laser (XFEL) pulses over a range of fluences from the linear to nonlinear x-ray absorption regimes as a function of system size, from a single atom to a cluster of 149 171 atoms. Fluorescence dynamics in the nonlinear x-ray regime differs from that in the weak x-ray field in that intense x-ray pulses interrupt the fluorescence dynamics by multiphoton absorption creating a dense electron environment within the sample on a femtosecond timescale. In large systems, the presence of both recombination and photoionization pathways gives rise to an enhanced Kα and Kα h emission yield and an extended emission time beyond the lifetime of the core-excited states. Our analysis suggests that, in an intense x-ray pulse, the Kα h emission line can be a good candidate for fluorescence imaging as it has a higher yield and an emission time that is short relative to the x-ray-induced lattice distortion time.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

What atoms do when they get together

How atoms organize during the earliest stages of nucleation has been a subject of speculation for over a century. Using atomically resolved electron microscopy, the formation and ordering of metal clusters from individual atoms has now been observed in carbon nanotubes that serve as ‘test tubes’.

De Yoreo, James J.↗
DOE OSTI2021

Thermal gradient effect on helium and self-interstitial transport in tungsten

First-wall materials in a fusion reactor are expected to withstand harsh conditions, with high heat and particle fluxes that modify the materials microstructure. These fluxes will create strong gradients of temperature and concentration of diverse species. Besides the He ash and the hydrogenic species, neutron particles generated in the fusion reaction will collide with the material creating intrinsic defects, such as vacancies, self-interstitials atoms (SIAs), and clusters of such point defects. These defects and the He atoms will then migrate in the presence of the aforementioned gradients. In this study, we use nonequilibrium molecular dynamics to analyze the transport of He and SIAs in the presence of a thermal gradient in tungsten. We observe that, in all cases, the defects and impurity atoms tend to migrate toward the hot regions of the tungsten sample. The resulting species concentration profiles are exponential distributions, rising toward the hot regions of the sample, in agreement with irreversible thermodynamics analysis. For both He atoms and SIAs, we find that the resulting species flux is directed opposite to the heat flux, indicating that species transport is governed by a Soret effect (thermal-gradient-driven diffusion) characterized by a negative heat of transport that drives species diffusion uphill (from the cooler to the hot regions of the sample). Here, we demonstrate that the steady-state species profiles obtained accounting for the Soret effect vary significantly from those where temperature-gradient-driven transport is not considered and discuss the implications of such a Soret effect on the response to plasma exposure of plasma-facing tungsten.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Generalized representative structures for atomistic systems

A new method is presented to generate atomic structures that reproduce the essential characteristics of arbitrary material systems, phases, or ensembles. Previous methods allow one to reproduce the essential characteristics (e.g. the chemical disorder) of a large random alloy within a small crystal structure. The ability to generate small representations of random alloys, along with the restriction to crystal systems, results from using the fixed-lattice cluster correlations to describe structural characteristics. A more general description of the structural characteristics of atomic systems is obtained using complete sets of atomic environment descriptors. These are used within for generating representative atomic structures without restriction to fixed lattices. A general data-driven approach is provided here utilizing the atomic cluster expansion (ACE) basis. The N-body ACE descriptors are a complete set of atomic environment descriptors that span both chemical and spatial degrees of freedom and are used within for describing atomic structures. The generalized representative structure (GRS) method presented within generates small atomic structures that reproduce ACE descriptor distributions corresponding to arbitrary structural and chemical complexity. It is shown that systematically improvable representations of crystalline systems on fixed parent lattices, amorphous materials, liquids, and ensembles of atomic structures may be produced efficiently through optimization algorithms. With the GRS method, we highlight reduced representations of atomistic machine-learning training datasets that contain similar amounts of information and small 40–72 atom representations of liquid phases. The ability to use GRS methodology as a driver for informed novel structure generation is also demonstrated. The advantages over other data-driven methods and state-of-the-art methods restricted to high-symmetry systems are highlighted.

atomic cluster expansion↗
DOE OSTI2020

Materials Data on Ni(ClO2)2 by Materials Project

NiO4NiCl4NiO4ClO2ClO2 crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of one 67952-07-2 molecule, one oxygen molecule, one NiCl4 cluster, one NiO4 cluster, and one NiO4Cl cluster. In the NiCl4 cluster, Ni is bonded in a tetrahedral geometry to four Cl atoms. There are three shorter (2.16 Å) and one longer (2.19 Å) Ni–Cl bond lengths. There are four inequivalent Cl sites. In the first Cl site, Cl is bonded in a single-bond geometry to one Ni atom. In the second Cl site, Cl is bonded in a single-bond geometry to one Ni atom. In the third Cl site, Cl is bonded in a single-bond geometry to one Ni atom. In the fourth Cl site, Cl is bonded in a single-bond geometry to one Ni atom. In the NiO4 cluster, Ni is bonded in a trigonal planar geometry to three O atoms. There is two shorter (1.60 Å) and one longer (1.95 Å) Ni–O bond length. There are four inequivalent O sites. In the first O site, O is bonded in a distorted bent 120 degrees geometry to one Ni and one O atom. The O–O bond length is 1.25 Å. In the second O site, O is bonded in a single-bond geometry to one O atom. In the third O site, O is bonded in a single-bond geometry to one Ni atom. In the fourth O site, O is bonded in a single-bond geometry to one Ni atom. In the NiO4Cl cluster, Ni is bonded in a T-shaped geometry to three O atoms. There are a spread of Ni–O bond distances ranging from 1.76–2.04 Å. There are four inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.24 Å. In the second O site, O is bonded in a bent 120 degrees geometry to one Ni and one O atom. In the third O site, O is bonded in a single-bond geometry to one Ni atom. In the fourth O site, O is bonded in a bent 120 degrees geometry to one Ni and one Cl atom. The O–Cl bond length is 1.62 Å. Cl is bonded in a single-bond geometry to one O atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SbXe2OF15 by Materials Project

XeF5XeOF4SbF6 crystallizes in the monoclinic P2_1/m space group. The structure is zero-dimensional and consists of two SbF6 clusters, two XeF5 clusters, and two XeOF4 clusters. In each SbF6 cluster, Sb is bonded in an octahedral geometry to six F atoms. There are a spread of Sb–F bond distances ranging from 1.89–1.97 Å. There are five inequivalent F sites. In the first F site, F is bonded in a distorted single-bond geometry to one Sb atom. In the second F site, F is bonded in a single-bond geometry to one Sb atom. In the third F site, F is bonded in a single-bond geometry to one Sb atom. In the fourth F site, F is bonded in a single-bond geometry to one Sb atom. In the fifth F site, F is bonded in a single-bond geometry to one Sb atom. In each XeF5 cluster, Xe is bonded in a 5-coordinate geometry to five F atoms. There are a spread of Xe–F bond distances ranging from 1.95–1.98 Å. There are three 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 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. All Xe–F bond lengths are 2.03 Å. O is bonded in a single-bond geometry to one Xe atom. There are two 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.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pt4(O3F8)3 by Materials Project

(PtF6)2PtOF6PtO3F5(O2)2OF crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of one hypofluorous acid molecule, two oxygen molecules, two PtF6 clusters, one PtO3F5 cluster, and one PtOF6 cluster. In each PtF6 cluster, Pt is bonded in an octahedral geometry to six F atoms. There are a spread of Pt–F bond distances ranging from 1.90–1.93 Å. There are six inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one Pt atom. In the second F site, F is bonded in a single-bond geometry to one Pt atom. In the third F site, F is bonded in a single-bond geometry to one Pt atom. In the fourth F site, F is bonded in a single-bond geometry to one Pt atom. In the fifth F site, F is bonded in a single-bond geometry to one Pt atom. In the sixth F site, F is bonded in a single-bond geometry to one Pt atom. In the PtO3F5 cluster, Pt is bonded in an octahedral geometry to one O and five F atoms. The Pt–O bond length is 2.16 Å. There are a spread of Pt–F bond distances ranging from 1.91–2.17 Å. There are three inequivalent O sites. In the first O site, O is bonded in a bent 120 degrees geometry to one Pt and one O atom. The O–O bond length is 1.24 Å. In the second O site, O is bonded in a single-bond geometry to one F atom. The O–F bond length is 1.42 Å. In the third O site, O is bonded in a single-bond geometry to one O atom. There are five inequivalent F sites. In the first F site, F is bonded in a bent 120 degrees geometry to one Pt and one O atom. In the second F site, F is bonded in a single-bond geometry to one Pt atom. In the third F site, F is bonded in a single-bond geometry to one Pt atom. In the fourth F site, F is bonded in a single-bond geometry to one Pt atom. In the fifth F site, F is bonded in a single-bond geometry to one Pt atom. In the PtOF6 cluster, Pt is bonded in an octahedral geometry to six F atoms. There are a spread of Pt–F bond distances ranging from 1.91–2.25 Å. O is bonded in a single-bond geometry to one F atom. The O–F bond length is 1.40 Å. There are six inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one Pt atom. In the second F site, F is bonded in a single-bond geometry to one Pt atom. In the third F site, F is bonded in a bent 120 degrees geometry to one Pt and one O atom. In the fourth F site, F is bonded in a single-bond geometry to one Pt atom. In the fifth F site, F is bonded in a single-bond geometry to one Pt atom. In the sixth F site, F is bonded in a single-bond geometry to one Pt atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KH28S4N7O16 by Materials Project

(KNH5O4)2(H2)6(NHO)2(HNO2)2(H2S)2(NH4SO)2(N2H3SO)2(NO)2(H2O)4H2O2(SO3H)2 crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of one aminohydroperoxide molecule, three hydrogen molecules, one hydrogen sulfide molecule, one hydroxylamine molecule, one hydroxylamine molecule, two water molecules, one water molecule, one KNH5O4 cluster, one N2H3SO cluster, one NH4SO cluster, and one SO3H cluster. In the KNH5O4 cluster, K1+ is bonded in a 2-coordinate geometry to one H1+ and one O2- atom. The K–H bond length is 2.41 Å. The K–O bond length is 2.64 Å. N+1.57+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.20 Å) and one longer (2.12 Å) N–O bond length. There are five inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one H1+ atom. The H–H bond length is 0.75 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the fourth H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.64 Å) H–O bond length. In the fifth H1+ site, H1+ is bonded in a distorted L-shaped geometry to one K1+ and one H1+ atom. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to one K1+ and two H1+ atoms. In the second O2- site, O2- is bonded in a 1-coordinate geometry to one N+1.57+, one H1+, and one O2- atom. The O–O bond length is 1.44 Å. In the third O2- site, O2- is bonded in a single-bond geometry to one N+1.57+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one H1+ and one O2- atom. In the N2H3SO cluster, there are two inequivalent N+1.57+ sites. In the first N+1.57+ site, N+1.57+ is bonded in a single-bond geometry to one S2- atom. The N–S bond length is 1.48 Å. In the second N+1.57+ site, N+1.57+ is bonded in a bent 120 degrees geometry to one H1+ and one S2- atom. The N–H bond length is 1.03 Å. The N–S bond length is 1.55 Å. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one S2- atom. The H–S bond length is 1.42 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N+1.57+ atom. S2- is bonded in a tetrahedral geometry to two N+1.57+, one H1+, and one O2- atom. The S–O bond length is 1.74 Å. O2- is bonded in a distorted water-like geometry to one H1+ and one S2- atom. In the NH4SO cluster, N+1.57+ is bonded in a distorted trigonal non-coplanar geometry to two H1+ and one S2- atom. Both N–H bond lengths are 1.03 Å. The N–S bond length is 1.66 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 1.00 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N+1.57+ atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one S2- atom. The H–S bond length is 1.35 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one N+1.57+ atom. S2- is bonded in a 3-coordinate geometry to one N+1.57+, one H1+, and one O2- atom. The S–O bond length is 1.65 Å. O2- is bonded in a distorted water-like geometry to one H1+ and one S2- atom. In the SO3H cluster, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. S2- is bonded in a water-like geometry to two O2- atoms. There is one shorter (1.51 Å) and one longer (1.75 Å) S–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to one S2- and one O2- atom. The O–O bond length is 1.44 Å. In the second O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the third O2- site, O2- is bonded in a single-bond geometry to one H1+ and one O2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on As2Kr3F16 by Materials Project

Kr2F3KrAsF7AsF6 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four AsF6 clusters, four Kr2F3 clusters, and four KrAsF7 clusters. In each AsF6 cluster, As is bonded in an octahedral geometry to six F atoms. There is three shorter (1.77 Å) and three longer (1.78 Å) As–F bond length. There are six inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one As atom. In the second F site, F is bonded in a single-bond geometry to one As atom. In the third F site, F is bonded in a single-bond geometry to one As atom. In the fourth F site, F is bonded in a single-bond geometry to one As atom. In the fifth F site, F is bonded in a single-bond geometry to one As atom. In the sixth F site, F is bonded in a single-bond geometry to one As atom. In each Kr2F3 cluster, there are two inequivalent Kr sites. In the first Kr site, Kr is bonded in a linear geometry to two F atoms. There is one shorter (1.85 Å) and one longer (2.09 Å) Kr–F bond length. In the second Kr site, Kr is bonded in a linear geometry to two F atoms. There is one shorter (1.85 Å) and one longer (2.09 Å) Kr–F bond length. There are three inequivalent F sites. In the first F site, F is bonded in a bent 120 degrees geometry to two Kr atoms. In the second F site, F is bonded in a single-bond geometry to one Kr atom. In the third F site, F is bonded in a single-bond geometry to one Kr atom. In each KrAsF7 cluster, Kr is bonded in a linear geometry to two F atoms. There is one shorter (1.85 Å) and one longer (2.09 Å) Kr–F bond length. As is bonded in an octahedral geometry to six F atoms. There are a spread of As–F bond distances ranging from 1.74–2.01 Å. There are seven inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one Kr atom. In the second F site, F is bonded in a bent 120 degrees geometry to one Kr and one As atom. In the third F site, F is bonded in a single-bond geometry to one As atom. In the fourth F site, F is bonded in a single-bond geometry to one As atom. In the fifth F site, F is bonded in a single-bond geometry to one As atom. In the sixth F site, F is bonded in a single-bond geometry to one As atom. In the seventh F site, F is bonded in a single-bond geometry to one As atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Ab Initio Molecular Dynamics Study of Pd Nucleation on a γ-Al 2 O 3 Surface

We perform ab initio molecular dynamics (AIMD) free energy simulations to investigate the stability and dynamics of dispersed Pd atoms and subnanometer clusters on γ-Al 2 O 3 . We consider nucleation for varying Pd loadings on dry γ-Al 2 O 3 (100), dry γ-Al 2 O 3 (110) and wet γ-Al 2 O 3 (110) and examine temperature, entropy and water coverage effects on the stability and dynamics of Pd clusters. At low Pd loading (1.07 Pd atoms/nm 2 on the (100) and 0.75 Pd/nm 2 on the (110)), association of the Pd atoms is thermodynamically unfavorable on the dry surfaces and almost thermoneutral on the wet (110) owing to water blocking of the AlIII defect sites. In agreement with past studies, the Pd atoms are quite mobile but the diffusion free energy barriers do not increase with the water coverage, as previously suggested, but rather remain similar in magnitude owing to translational entropy at finite temperatures. At these Pd loadings, oxidized Pd(II) atoms on the wet (110) surface are dispersed and immobile. At higher Pd loading (1.12 and 1.5 Pd atoms/nm 2 ) on the (110) surface, Pd 3 and Pd 4 clusters are thermodynamically very stable and form fast. At the 1.12 Pd atoms/nm 2 loading, the formation of the Pd 3 cluster is two orders of magnitude slower when the surface is hydroxylated as the system becomes somewhat trapped before the dinuclear cluster Pd 2 collides with a Pd atom.

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

Atomic Layer Deposition for Preparing Isolated Co Sites on SiO 2 for Ethane Dehydrogenation Catalysis

Unlike Co clusters, isolated Co atoms have been shown to be selective for catalytic dehydrogenation of ethane to ethylene; however, preparation of isolated Co sites requires special preparation procedures. Here, we demonstrate that Atomic Layer Deposition (ALD) of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)cobalt(III) (Co(TMHD) 3 ) on silica and other supports is effective in producing these isolated species. Silica-supported catalysts prepared with one ALD cycle showed ethylene selectivities greater than 96% at 923 K and were stable when CO 2 was co-fed with the ethane. Co catalysts prepared by impregnation formed clusters that were significantly less active, selective, and stable. Rates and selectivities also decreased for catalysts with multiple ALD cycles. Isolated Co catalysts prepared on Al 2 O 3 and MgAl 2 O 4 showed reasonable selectivity for ethane dehydrogenation but were not as effective as their silica counterpart.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AgAsS16N16(O4F3)2 by Materials Project

AgS12(N2O)6(N2S2O)2AsF6 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two AgS12(N2O)6 clusters, two AsF6 clusters, and two N2S2O clusters. In each AgS12(N2O)6 cluster, Ag1+ is bonded in a 1-coordinate geometry to three O2- atoms. There are a spread of Ag–O bond distances ranging from 2.83–3.24 Å. There are twelve inequivalent N3+ sites. In the first N3+ site, N3+ is bonded in a bent 120 degrees geometry to two S2- atoms. There is one shorter (1.60 Å) and one longer (1.64 Å) N–S bond length. In the second N3+ site, N3+ is bonded in a bent 150 degrees geometry to two S2- atoms. There is one shorter (1.55 Å) and one longer (1.58 Å) N–S bond length. In the third N3+ site, N3+ is bonded in a bent 150 degrees geometry to two S2- atoms. There is one shorter (1.56 Å) and one longer (1.60 Å) N–S bond length. In the fourth N3+ site, N3+ is bonded in a bent 120 degrees geometry to two S2- atoms. There is one shorter (1.58 Å) and one longer (1.64 Å) N–S bond length. In the fifth N3+ site, N3+ is bonded in a bent 120 degrees geometry to two S2- atoms. There is one shorter (1.59 Å) and one longer (1.65 Å) N–S bond length. In the sixth N3+ site, N3+ is bonded in a bent 150 degrees geometry to two S2- atoms. There is one shorter (1.56 Å) and one longer (1.59 Å) N–S bond length. In the seventh N3+ site, N3+ is bonded in a bent 150 degrees geometry to two S2- atoms. There is one shorter (1.57 Å) and one longer (1.59 Å) N–S bond length. In the eighth N3+ site, N3+ is bonded in a bent 120 degrees geometry to two S2- atoms. There is one shorter (1.57 Å) and one longer (1.63 Å) N–S bond length. In the ninth N3+ site, N3+ is bonded in a bent 120 degrees geometry to two S2- atoms. There is one shorter (1.59 Å) and one longer (1.65 Å) N–S bond length. In the tenth N3+ site, N3+ is bonded in a bent 150 degrees geometry to two S2- atoms. There is one shorter (1.56 Å) and one longer (1.59 Å) N–S bond length. In the eleventh N3+ site, N3+ is bonded in a bent 150 degrees geometry to two S2- atoms. There is one shorter (1.57 Å) and one longer (1.59 Å) N–S bond length. In the twelfth N3+ site, N3+ is bonded in a bent 120 degrees geometry to two S2- atoms. There is one shorter (1.57 Å) and one longer (1.63 Å) N–S bond length. There are twelve inequivalent S2- sites. In the first S2- site, S2- is bonded in a bent 120 degrees geometry to two N3+ atoms. In the second S2- site, S2- is bonded in a bent 120 degrees geometry to two N3+ atoms. In the third S2- site, S2- is bonded in a distorted bent 120 degrees geometry to two N3+ atoms. In the fourth S2- site, S2- is bonded in a bent 120 degrees geometry to two N3+ atoms. In the fifth S2- site, S2- is bonded in a bent 120 degrees geometry to two N3+ atoms. In the sixth S2- site, S2- is bonded in a bent 120 degrees geometry to two N3+ atoms. In the seventh S2- site, S2- is bonded in a tetrahedral geometry to two N3+ and two O2- atoms. There is one shorter (1.44 Å) and one longer (1.45 Å) S–O bond length. In the eighth S2- site, S2- is bonded in a bent 120 degrees geometry to two N3+ atoms. In the ninth S2- site, S2- is bonded in a bent 120 degrees geometry to two N3+ atoms. In the tenth S2- site, S2- is bonded in a tetrahedral geometry to two N3+ and two O2- atoms. Both S–O bond lengths are 1.45 Å. In the eleventh S2- site, S2- is bonded in a tetrahedral geometry to two N3+ and two O2- atoms. There is one shorter (1.44 Å) and one longer (1.45 Å) S–O bond length. In the twelfth S2- site, S2- is bonded in a distorted bent 120 degrees geometry to two N3+ atoms. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Ag1+ and one S2- atom. In the second O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the third O2- site, O2- is bonded in a single-bond geometry to one Ag1+ and one S2- atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one Ag1+ and one S2- atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In each AsF6 cluster, As5+ is bonded in an octahedral geometry to six F1- atoms. There is one shorter (1.77 Å) and five longer (1.78 Å) As–F bond length. There are six inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the fifth F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the sixth F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In each N2S2O cluster, there are four inequivalent N3+ sites. In the first N3+ site, N3+ is bonded in a bent 150 degrees geometry to two S2- atoms. There is one shorter (1.56 Å) and one longer (1.59 Å) N–S bond length. In the second N3+ site, N3+ is bonded in a bent 120 degrees geometry to two S2- atoms. There is one shorter (1.57 Å) and one longer (1.63 Å) N–S bond length. In the third N3+ site, N3+ is bonded in a bent 120 degrees geometry to two S2- atoms. There is one shorter (1.59 Å) and one longer (1.65 Å) N–S bond length. In the fourth N3+ site, N3+ is bonded in a bent 150 degrees geometry to two S2- atoms. There is one shorter (1.56 Å) and one longer (1.60 Å) N–S bond length. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a tetrahedral geometry to two N3+ and two O2- atoms. There is one shorter (1.44 Å) and one longer (1.45 Å) S–O bond length. In the second S2- site, S2- is bonded in a bent 120 degrees geometry to two N3+ atoms. In the third S2- site, S2- is bonded in a bent 120 degrees geometry to two N3+ atoms. In the fourth S2- site, S2- is bonded in a bent 120 degrees geometry to two N3+ atoms. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the second O2- site, O2- is bonded in a single-bond geometry to one S2- atom.

36 MATERIALS SCIENCE↗