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DOE OSTI2023

Online Analytics for Remedy Support at DOE Environmental Management Sites

Environmental data is important for managing environmental restoration/waste site remediation, planning of monitoring efforts, addressing climate resilience, and engaging with stakeholders and regulators. A major challenge is how to manage the many different types and the large volume of environmental data in a way that allows practitioners and site managers to understand data implications and support decisions. The Suite Of Comprehensive Rapid Analysis Tools for Environmental Sites (SOCRATES, https://www.pnnl.gov/projects/socrates) is a web application that provides data access, visualization, and rapid analytics to help make sense of environmental data, support remedy decisions, and communicate information. Development of SOCRATES has been funded through the DOE Richland Operations Office (RL) to support communication and decision making for the Hanford Site, thus is only tied into Hanford environmental data. However, the capabilities of SOCRATES are more broadly applicable to DOE-EM sites engaged in environmental remediation and management. This report describes the work to develop mechanisms for bringing non-Hanford data into SOCRATES so that other DOE-EM sites could make use of the visualization and analysis capabilities to support communication and decision making related to managing environmental restoration/waste site remediation, optimization/exit strategies for pump-and-treat systems, planning monitoring efforts, addressing climate resilience, and/or engaging with stakeholders and regulators. The background, approach, data transfer formats, examples, and next steps for this new SOCRATES-EM software are described in this report.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Can Collaboration Succeed in Siting a Spent Nuclear Fuel Facility in the United States?—A Challenge in Political Sustainability

We examine the U.S. Department of Energy (DOE)’s collaborative process to locate, build, and operate one or more federal consolidated interim storage facilities (FCISFs) for commercial U.S. spent nuclear fuel—instead of continuing to store the material at over 70 nuclear reactor sites. Technocratic siting of nuclear facilities in the U.S., most of which did not involve meaningful public participation, was not successful. We consider increasing pressure to find at least one FCISF site, as well as the critical role of trust in engaging communities and reaching agreement—leading some observers to assert that DOE is in the “trust building business”, not the siting business. We present case studies with the following: (1) illustrating community engagement that led to a more satisfactory outcome than had been anticipated (Fernald); (2) a planned voluntary process that failed to produce an operating CISF (Office of the Nuclear Waste Negotiator); and (3) a site that demonstrates the ongoing need for negotiations to keep a site open and operational (Waste Isolation Pilot Plant). The essay concludes with the observation that a collaboration-based siting effort can succeed in the U.S., but that five main challenges—related to trust and requiring patience—will need to be addressed.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

German research and development for high level waste in light of the new site selection process - 15516

The German government decided 50 years ago, that radioactive waste is to be disposed of in Deep Geologic Repositories, preferably in a salt rock formation. Soon after, in 1967, research in the Asse salt mine was initiated. Since then substantial progress has been achieved in the development of the radioactive waste disposal programme in Germany. For a geologic repository for High Level Waste in salt a reference concept has been developed, which represented the radioactive waste management processes from transport of High Level Waste and Spent Nuclear Fuel to an interim storage site, waste conditioning and repackaging for disposal, to emplacement of the waste packages. The feasibility of the reference concept has been proven by demonstration tests for all relevant equipment: a pilot conditioning plant has been built as well as the main equipment for the entire transport chain including the shaft transport and emplacement technologies for heavy loads fulfilling strict requirements for nuclear and mining safety. Also the backfilling technology has been optimised for the purposes of a repository for radioactive waste. Finally, tests have been performed to verify thermo-mechanical models for the host rock. The demonstration tests have been performed to an extent which even would allow immediate licensing of the repository and the employed equipment. The Research and Development work was completed by further optimisation of the reference concept. Construction and operation of deep geologic repositories for low and intermediate level radioactive wastes in Germany benefited from the above mentioned but also stimulated the knowledge and experience build-up for the repositories for High Level Waste. Despite the well progressed work for a deep geologic repository in salt R and D work in Germany for already a long time also considered other host rock formations. While work for crystalline rock mainly consisted of relatively small contributions to international research projects due to the limited occurrence of suitable sites in Germany, projects and developments for repositories in clay formations have had an increasing contribution to the overall Research and Development work for radioactive waste repositories in Germany. In July 2013 a new site selection act was put into force, which set the initiating conditions for the German programme on radioactive waste management. Principally, a process was initiated to search for a site for a deep geologic repository for High Level Waste independent from earlier decisions. This means that a site shall be determined without predetermination by earlier decisions. Nevertheless, to enable a sound decision for a site selection it is necessary to be able draw back on the knowledge and experience from earlier activities. Otherwise, tedious learning processes would have to be experienced again. Since efforts to open up a site selection process again grew since the late 1990's projects had been implemented timely to capture existing knowledge. The paper at hand describes the achievements of R and D activities in Germany, the change of radioactive waste management policy and the endeavours to maintain the achievements. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Indoor Dust Remedial Investigation Sampling at the Colonie FUSRAP Site - 15578

The Colonie Formerly Utilized Sites Remedial Action Program (FUSRAP) Site is located in the Town of Colonie, Albany County, New York. The U.S. Army Corps of Engineers (USACE) is currently addressing environmental contamination associated with the Site. The area surrounding the Site consists of residential and commercial properties, known as vicinity properties. Cleanup activities have been completed on many of these VPs under the FUSRAP to address depleted uranium contamination. Soil remediation activities have been substantially completed at the Colonie FUSRAP Site and its VPs under the FUSRAP. Recent studies performed by an independent party and under FUSRAP identified uranium within indoor dust in residencies and businesses in the immediate vicinity of the Site. The studies were limited to non-living areas such as basement window sills, garages, and attics. This paper discusses the indoor dust Remedial Investigation (RI) for the VPs at the Colonie FUSRAP Site. The indoor dust sample media presented many technical challenges regarding sampling design, data reduction, and data interpretation. In addition, because the RI is focused on numerous resident-owned, rental, and commercial properties, challenges where presented regarding right-of-entry to sample and concerns were raised regarding confidentiality of the results. In response to this, a community outreach communication and education program is being developed to mitigate property-owner concerns. The paper also identifies specific action levels used to determine future actions. Ultimately, property-specific risk assessments, performed at properties exceeding the action levels, will be used to determine whether a response action is appropriate under FUSRAP. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Atomic Structure Evolution of Pt–Co Binary Catalysts: Single Metal Sites versus Intermetallic Nanocrystals

Due to their exceptional catalytic properties for the oxygen reduction reaction (ORR) and other crucial electrochemical reactions, PtCo intermetallic nanoparticle (NP) and single atomic (SA) Pt metal site catalysts have received considerable attention. However, their formation mechanisms at the atomic level during high-temperature annealing processes remain elusive. Furthermore, the thermally driven structure evolution of Pt–Co binary catalyst systems is investigated using advanced in situ electron microscopy, including PtCo intermetallic alloys and single Pt/Co metal sites. The pre-doping of CoN 4 sites in carbon supports and the initial Pt NP sizes play essential roles in forming either Pt 3 Co intermetallics or single Pt/Co metal sites. Importantly, the initial Pt NP loadings against the carbon support are critical to whether alloying to L1 2 -ordered Pt 3 Co NPs or atomizing to SA Pt sites at high temperatures. High Pt NP loadings (e.g., 20%) tend to lead to the formation of highly ordered Pt 3 Co intermetallic NPs with excellent activity and enhanced stability toward the ORR. In contrast, at a relatively low Pt loading (<6 wt%), the formation of single Pt sites in the form of PtC 3 N is thermodynamically favorable, in which a synergy between the PtC 3 N and the CoN 4 sites could enhance the catalytic activity for the ORR, but showing insufficient stability.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Atomically Dispersed Single Ni Site Catalysts for Nitrogen Reduction toward Electrochemical Ammonia Synthesis Using N 2 and H 2 O

Ammonia (NH 3 ) electrosynthesis gains significant attention as NH 3 is essentially important for fertilizer production and fuel utilization. However, electrochemical nitrogen reduction reaction (NRR) remains a great challenge because of low activity and poor selectivity. Herein, a new class of atomically dispersed Ni site electrocatalyst is reported, which exhibits the optimal NH 3 yield of 115 µg cm -2 h -1 at –0.8 V versus reversible hydrogen electrode (RHE) under neutral conditions. High faradic efficiency of 21 ± 1.9% is achieved at -0.2 V versus RHE under alkaline conditions, although the ammonia yield is lower. The Ni sites are stabilized with nitrogen, which is verified by advanced X-ray absorption spectroscopy and electron microscopy. Density functional theory calculations provide insightful understanding on the possible structure of active sites, relevant reaction pathways, and confirm that the Ni-N 3 sites are responsible for the experimentally observed activity and selectivity. Extensive controls strongly suggest that the atomically dispersed NiN 3 site-rich catalyst provides more intrinsically active sites than those in N-doped carbon, instead of possible environmental contamination. Overall, this work further indicates that single-metal site catalysts with optimal nitrogen coordination is very promising for NRR and indeed improves the scaling relationship of transition metals.

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

Improving Long-term Monitoring of Contaminated Groundwater at Sites where Attenuation-based Remedies are Deployed

This study presents an effective approach to tackle the challenge of long-term monitoring of contaminated groundwater sites where remediation leaves residual contamination in the subsurface. Traditional long-term monitoring of contaminated groundwater sites focuses on measuring contaminant concentrations and is applicable to sites where contaminant mass is removed or degraded to a level below the regulatory standard. The traditional approach is less effective at sites where risk from metals or radionuclides continues to exist in the subsurface after remedial goals are achieved. We propose a long-term monitoring strategy for this type of waste site that focuses on measuring the hydrological and geochemical parameters that control attenuation or remobilization of contaminants while de-emphasizing contaminant-concentration measurements. Furthermore, we demonstrate how this approach would be more effective than traditional long-term monitoring, using a site in South Carolina, USA, where groundwater is contaminated by several radionuclides. A comprehensive enhanced attenuation remedy has been implemented at the site to minimize discharge of contamination to surface water. The immobilization of contaminants occurs in three locations by manipulation of hydrological and geochemical parameters, as well as by natural attenuation processes. Deployment of our proposed long-term monitoring strategy will combine subsurface and surface measurements using spectroscopic tools, geophysical tools, and sensors to monitor the parameters controlling contaminant attenuation. The advantage of this approach is that it will detect the potential for contaminant remobilization from engineered and natural attenuation zones, allowing potential adverse changes to be mitigated before contaminant attenuation is reversed.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2011

Bayesian hierarchical models for soil CO{sub 2} flux and leak detection at geologic sequestration sites

Proper characterizations of background soil CO{sub 2} respiration rates are critical for interpreting CO{sub 2} leakage monitoring results at geologic sequestration sites. In this paper, a method is developed for determining temperature-dependent critical values of soil CO{sub 2} flux for preliminary leak detection inference. The method is illustrated using surface CO{sub 2} flux measurements obtained from the AmeriFlux network fit with alternative models for the soil CO{sub 2} flux versus soil temperature relationship. The models are fit first to determine pooled parameter estimates across the sites, then using a Bayesian hierarchical method to obtain both global and site-specific parameter estimates. Model comparisons are made using the deviance information criterion (DIC), which considers both goodness of fit and model complexity. The hierarchical models consistently outperform the corresponding pooled models, demonstrating the need for site-specific data and estimates when determining relationships for background soil respiration. A hierarchical model that relates the square root of the CO{sub 2} flux to a quadratic function of soil temperature is found to provide the best fit for the AmeriFlux sites among the models tested. This model also yields effective prediction intervals, consistent with the upper envelope of the flux data across the modeled sites and temperature ranges. Calculation of upper prediction intervals using the proposed method can provide a basis for setting critical values in CO{sub 2} leak detection monitoring at sequestration sites.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Deep Vadose Zone Contaminant Flux Evaluation at the Hanford BY-Cribs Site using Forward and Imposed Concentration Modeling Approaches

For sites with vadose zone contamination, the nature and extent of groundwater contaminant plumes are related to the flux into groundwater. In thick vadose zones at arid sites, transport is likely relative slow, complicating direct measurement of contaminant flux. A predictive numerical analysis was applied to estimate contaminant flux to groundwater at the Hanford BY Cribs site. The site received large amounts of waste water in the 1950’s, containing contaminants such as technicium-99 and nitrate. Recently, large increases in groundwater concentrations have been observed in site groundwater wells and, for potential remediation purposes, the assumption that the changes are the result of increased vadose zone fluxes into groundwater needed to be evaluated. The analysis approach uses forward simulations, tracking contaminants during and after disposal, and imposed concentration (IC) simulations, where concentrations, derived from electrical conductivity data obtained in 2007, are imposed on the flow field. A total of three IC methods, relating electrical conductivity to nitrate concentrations, are developed and tested. The numerical analysis shows that the forward simulations predict high fluxes during and directly after disposal, with decreasing trends starting not later than 1970. Although the IC simulations show differences in the nitrate vadose zone mass imposed in 2007 compared to forward simulations, the IC simulations also show declining nitrate fluxes over time. The predicted fluxes of the forward and IC simulations after 2007 are in reasonable agreement. Given the declining nature of the contaminant fluxes, it can be concluded that the observed concentration increases in the groundwater below the BY Cribs site cannot be explained as resulting from an increase in contaminant flux from the vadose zone. An alternative explanation, based on the observed decrease in aquifer thickness below the site, is presented.

Oostrom, Martinus↗
DOE OSTI2011

Identification and clarification of the role of key active site residues in bacterial glutathione S-transferase zeta/maleylpyruvate isomerase

Highlights: {yields} Application of site-directed mutagenesis to probe the active site residues of glutathione-dependent maleylpyruvate isomerase. {yields} Two conserved residues, Arg8 and Arg176, in zeta class glutathione S-transferases are critical for maleylpyruvate orientation and enolization. {yields} Arg109, found exclusively in NagL, participates in k{sub cat} regulation. {yields} The T11A mutant exhibited a significantly decreased K{sub m} value for glutathione with little impact on maleylpyruvate kinetics. {yields} The Thr11 residue appears to have significance in the evolution of glutathione S-transferase classes. -- Abstract: The maleylpyruvate isomerase NagL from Ralstonia sp. strain U2, which has been structurally characterized previously, catalyzes the isomerization of maleylpyruvate to fumarylpyruvate. It belongs to the class zeta glutathione S-transferases (GSTZs), part of the cytosolic GST family (cGSTs). In this study, site-directed mutagenesis was conducted to probe the functions of 13 putative active site residues. Steady-state kinetic information for mutants in the reduced glutathione (GSH) binding site, suggested that (a) Gln64 and Asp102 interact directly with the glutamyl moiety of glutathione, (b) Gln49 and Gln64 are involved in a potential electron-sharing network that influences the ionization of the GSH thiol. The information also suggests that (c) His38, Asn108 and Arg109 interact with the GSH glycine moiety, (d) His104 has a role in the ionization of the GSH sulfur and the stabilization of the maleyl terminal carboxyl group in the reaction intermediate and (e) Arg110 influences the electron distribution in the active site and therefore the ionization of the GSH thiolate. Kinetic data for mutants altered in the substrate-binding site imply that (a) Arg8 and Arg176 are critical for maleylpyruvate orientation and enolization, and (b) Arg109 (exclusive to NagL) participates in k{sub cat} regulation. Surprisingly, the T11A mutant had a decreased GSH K{sub m} value, whereas little impact on maleylpyruvate kinetics was observed, suggesting that this residue plays an important role in GSH binding. An evolutionary trend in this residue appears to have developed not only in prokaryotic and eukaryotic GSTZs, but also among the wider class of cGSTs.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Predicting on-site environmental impacts of municipal engineering works

The research findings fill a gap in the body of knowledge by presenting an effective way to evaluate the significance of on-site environmental impacts of municipal engineering works prior to the construction stage. First, 42 on-site environmental impacts of municipal engineering works were identified by means of a process-oriented approach. Then, 46 indicators and their corresponding significance limits were determined on the basis of a statistical analysis of 25 new-build and remodelling municipal engineering projects. In order to ensure the objectivity of the assessment process, direct and indirect indicators were always based on quantitative data from the municipal engineering project documents. Finally, two case studies were analysed and found to illustrate the practical use of the proposed model. The model highlights the significant environmental impacts of a particular municipal engineering project prior to the construction stage. Consequently, preventive actions can be planned and implemented during on-site activities. The results of the model also allow a comparison of proposed municipal engineering projects and alternatives with respect to the overall on-site environmental impact and the absolute importance of a particular environmental aspect. These findings are useful within the framework of the environmental impact assessment process, as they help to improve the identification and evaluation of on-site environmental aspects of municipal engineering works. The findings may also be of use to construction companies that are willing to implement an environmental management system or simply wish to improve on-site environmental performance in municipal engineering projects. -- Highlights: • We present a model to predict the environmental impacts of municipal engineering works. • It highlights significant on-site environmental impacts prior to the construction stage. • Findings are useful within the environmental impact assessment process. • They also help contractors to implement environmental management systems.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Interactions of Wind Energy Project Siting, Wind Resource Potential, and the Evolution of the U.S. Power System

The interactions of wind energy project siting, resource potential, and power system evolution are critical to understand given interest in high renewable energy systems, particularly as wind costs have fallen and grid operators implement solutions to manage variable generation. This study applies an integrative approach that combines spatially-explicit resource potential analysis with high spatial resolution U.S. electricity system modeling. Multiple wind supply curves, representing variations in siting regimes that account for interactions with built infrastructure, regulatory, physical, and social land use factors, are evaluated to determine how siting could influence prospective wind development. Different siting regimes lead to variations in future wind capacity, with the greatest impacts observed under scenarios with high demand for clean energy. With the tightest emissions limit modeled, 2050 onshore wind capacity varied by +7% (49 GW) in the least-restrictive siting regime to a decrease of 37% (270 GW) under the most-constrained case. More-stringent siting restrictions lead to higher electricity prices and emissions that should be weighed with local impacts. Under restrictive siting regimes, wind deployment is also sensitive to transmission availability and wind plant design. Overall, the findings highlight the importance of local land use considerations in regional and national power system planning.

17 WIND ENERGY↗
DOE OSTI2015

Assessment of contaminant levels and trophic relations at a World Heritage Site by measurements in a characteristic shorebird species

The River Elbe is responsible for influxes of contaminants into the Wadden Sea World Heritage Site. We investigated levels of polychlorinated biphenyls (PCBs), oxychlordane (OxC), hexachlorobenzene (HCB), hexachlorocyclohexanes (α-, β-, γ-HCHs), dichlorodiphenyltrichloroethane (DDT) and its metabolites, and polybrominated diphenyl ethers (PBDEs) in blood and feathers from Eurasian oystercatchers (Haematopus ostralegus; n=28) at the Elbe and compared it with a non-riverine site about 90 km further north. (1) Mean levels of all contaminants in feathers and serum were significantly higher at the river (∑PCBs: 27.6 ng/g feather, 37.0 ng/ml serum; ∑DDTs: 5.3 ng/g feather, 4.4 ng/ml serum) compared with the non-riverine site (∑PCBs: 6.5 ng/g feather, 1.2 ng/ml serum; ∑DDTs: 1.4 ng/g feather, 0.5 ng/ml serum). Mean ∑HCH and HCB levels were <1.8 ng/g in feather and <1.8 ng/ml in serum at both sites. (2) Levels of most detectable compounds in serum and feathers were significantly related, but levels were not consistently higher in either tissue. (3) There was no significant relationship between trophic level in individual oystercatchers (expressed as δ15N) or the degree of terrestrial feeding (expressed as δ13C) and contaminant loads. (4) PBDEs were not detected in significant amounts at either site. The results of this study indicate that the outflow from one of Europe′s largest river systems is associated with significant historical contamination, reflected by the accumulation of contaminants in body tissues in a coastal benthivore predator. - Highlights: • Contaminants in Oystercatchers from the Elbe river and a non-riverine site were measured. • Mean levels of contaminants were higher at the river than at the non-riverine site. • Levels of most contaminants in serum and feathers were significantly related. • No relationship between trophic level (δ15N) and contaminant level was found. • One of Europe′s largest river systems is associated with major historical contamination.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Quantitative site-specific reactivity profiling of S-nitrosylation in mouse skeletal muscle using cysteinyl peptide enrichment coupled with mass spectrometry

S-nitrosylation (SNO) is an important reversible thiol oxidation event that has been increasingly recognized for its role in cell signaling. While many proteins susceptible to S-nitrosylation have been reported, site-specific identification of physiologically relevant SNO modifications remains an analytical challenge due to the low-abundance and labile nature of the modification. Herein we present further improvement and optimization of the recently reported, resin-assisted cysteinyl peptide enrichment protocol for SNO identification and the extension of this application to mouse skeletal muscle to identify specific sites sensitive to S-nitrosylation by quantitative reactivity profiling. The results of our data indicate that the protein- and peptide-level enrichment protocols provide comparable specificity and coverage of SNO-peptide identifications. S-nitrosylation reactivity profiling was performed by quantitatively comparing the site-specific SNO modification levels in samples treated with S-nitrosoglutathione (GSNO), an NO donor, at two different physiologically relevant concentrations (i.e., 10 μM and 100 μM). The reactivity profiling experiments overall identified 489 SNO-modified cysteine sites from 197 proteins with the specificity of 95.2% at the unique-peptide-level based on the percentage of Cys-peptides. Among these sites, 260 sites from 135 proteins were observed with relatively high reactivity to S-nitrosylation; such SNO-sensitive sites are more likely to be physiologically relevant. Many of the SNO-sensitive proteins are preferentially localized in mitochondria, contractile fiber and actin cytoskeleton, suggesting the susceptibility of these subcellular compartments to redox regulation. Moreover, the SNO-sensitive proteins seem to be primarily involved in metabolic pathways, including TCA cycle, glycolysis/gluconeogenesis, glutathione metabolism, and fatty acid metabolism, suggesting the importance of redox regulation in muscle metabolism and insulin action.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Promotion of protolytic pentane conversion on H-MFI zeolite by proximity of extra-framework aluminum oxide and Brønsted acid sites

The activity of strong Brønsted acid sites in H-MFI zeolites for pentane cracking and dehydrogenation is enhanced by the presence of extra-framework aluminum in spatial proximity. The steric proximity of these two sites is deduced from the perturbation of OH groups on extra-framework aluminum oxide by pyridine or pentane adsorbed on Brønsted acid sites manifested in the IR spectra. The turnover frequencies of overall cracking and dehydrogenation on such sites are about 50 and 80 times higher than on isolated strong Brønsted acid sites. While pentane does not adsorb stronger, the site pair stabilizes cracking and dehydrogenation transition states mainly via increasing the activation entropy. This is interpreted as a later transition state for the cracking and dehydrogenation. The results suggest that controlled steaming can be used to enhance catalytic activity of zeolite Brønsted acid sites.

Zhang, Yang↗
DOE OSTI2012

Analysis of Binding Site Hot Spots on the Surface of Ras GTPase

We have recently discovered an allosteric switch in Ras, bringing an additional level of complexity to this GTPase whose mutants are involved in nearly 30% of cancers. Upon activation of the allosteric switch, there is a shift in helix 3/loop 7 associated with a disorder to order transition in the active site. Here, we use a combination of multiple solvent crystal structures and computational solvent mapping (FTMap) to determine binding site hot spots in the 'off' and 'on' allosteric states of the GTP-bound form of H-Ras. Thirteen sites are revealed, expanding possible target sites for ligand binding well beyond the active site. Comparison of FTMaps for the H and K isoforms reveals essentially identical hot spots. Furthermore, using NMR measurements of spin relaxation, we determined that K-Ras exhibits global conformational dynamics very similar to those we previously reported for H-Ras. We thus hypothesize that the global conformational rearrangement serves as a mechanism for allosteric coupling between the effector interface and remote hot spots in all Ras isoforms. At least with respect to the binding sites involving the G domain, H-Ras is an excellent model for K-Ras and probably N-Ras as well. Ras has so far been elusive as a target for drug design. The present work identifies various unexplored hot spots throughout the entire surface of Ras, extending the focus from the disordered active site to well-ordered locations that should be easier to target.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Atomistic study on the site preference and lattice vibration of Gd{sub 3−x}Y{sub x}Co{sub 29}T{sub 4}B{sub 10} (T=Al and Ge)

The effects of the Y substitution for Gd on the structural stability and the site preference of intermetallics Gd{sub 3−x}Y{sub x}Co{sub 29}T{sub 4}B{sub 10} (T=Al and Ge) are studied by using a series of interatomic pair potentials. The calculated results show Y can stabilize Gd{sub 3−x}Y{sub x}Co{sub 29}T{sub 4}B{sub 10} with the tetragonal structure, and Y substitute for Gd with a strong preference for the 2b sites. The calculated lattice parameters are in good agreement with the experimental data. Furthermore, the total and partial phonon densities of states are evaluated for the Gd{sub 3−x}Y{sub x}Co{sub 29}T{sub 4}B{sub 10} compounds with the tetragonal structure. A qualitative analysis is carried out with the relevant potentials for the vibrational modes, which makes it possible to predict some properties related to lattice vibration. - Graphical abstract: The lattice cell of Gd{sub 3}Co{sub 29}T{sub 4}B{sub 10} consists of 92 atoms, or two Gd{sub 3}Co{sub 29}T{sub 4}B{sub 10} formula units, with fourteen distinct kinds of site. Rare-earth atoms occupy 2b and 4d sites, Co atoms occupy the Co1(2c), Co2(8i1), Co3(8i2), Co4(8i3), Co5(8j1), Co6(8j2) and Co7(16k), T atoms occupy the T(8i) sites, and B atoms occupy the B1(2c1), B2(2c2), B3(8i) and B4(8j) sites. - Highlights: • The application of the pair potentials obtained from lattice-inversion method. • The lattice vibrations for Gd{sub 3−x}Y{sub x}Co{sub 29}T{sub 4}B{sub 10} (T=Ge and Al) are first evaluated. • The Y atoms should prefer the 2b site of Gd{sub 3−x}Y{sub x}Co{sub 29}T{sub 4}B{sub 10} compounds. • The total and partial phonon densities of states are evaluated for the Gd{sub 3−x}Y{sub x}Co{sub 29}T{sub 4}B{sub 10} compounds with the tetragonal structure. • A qualitative analysis is carried out with the relevant potentials for the vibrational modes.

36 MATERIALS SCIENCE↗
DOE OSTI2016

High-pressure synthesis and relationship between A-site ordering and local structure of multicomponent perovskites (Ln{sub 0.25}Mn{sub 0.75})(Al{sub 0.25}Ti{sub 0.75})O{sub 3}, Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Y

ABSTRACT: The synthesis of multicomponent perovskites (Ln{sub 0.25}Mn{sub 0.75})(Al{sub 0.25}Ti{sub 0.75})O{sub 3} (Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Y) have been investigated using a high-pressure and high-temperature (6 GPa, 1175 °C) technique. When Ln{sup 3+} is larger La{sup 3+}, Pr{sup 3+}, Nd{sup 3+}, the A-site ordered perovskites, LnMn{sub 3}(Al{sub 0.25}Ti{sub 0.75}){sub 4}O{sub 12} in Im-3, have been successfully synthesized. The A-site partially disordered one, (Sm{sub 0.80}Mn{sub 0.20})(Sm{sub 0.07}Mn{sub 0.93}){sub 3}(Al{sub 0.25}Ti{sub 0.75}){sub 4}O{sub 12} is also obtained. In the case of smaller Gd{sup 3+}, Tb{sup 3+}, Dy{sup 3+}, we have obtained no single phase but two decomposed perovskite phases. When Ln{sup 3+} is much smaller Y{sup 3+}, it is crystallized as an A-site disorder one in Pnma. The Rietveld structural refinements of the A-site ordered and partially disordered perovskites indicate that the tilting of (Al/Ti)O{sub 6} octahedrons for the A-site ions ordering is correlated with the (Al/Ti)–O and Ln–O bond lengths to optimize the coordination of the A- and A′-sites. The phase stability of the A-site ordered perovskites is discussed from the viewpoint of this correlation. - Graphical abstract: Ln{sup 3+} (VIII) ionic radius dependence of BO{sub 6} octahedron tilt angle and A/B–O distance of Im-3 perovskites (Ln{sub 0.25}Mn{sub 0.75})(Al{sub 0.25}Ti{sub 0.75})O{sub 3} (Ln=La-Sm).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗