Roger Rousseau

Oak Ridge National Laboratory

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Vassiliki‐Alexandra Glezakou

Battelle

Difan Zhang

Pacific Northwest National Laboratory

Deepika Malhotra

Pacific Northwest National Laboratory

David J. Heldebrant

Pacific Northwest National Laboratory

David C. Cantu

University of Nevada, Reno

Phillip Koech

Pacific Northwest National Laboratory

Mal‐Soon Lee

Pacific Northwest National Laboratory

Manh‐Thuong Nguyen

Pacific Northwest National Laboratory

Sarah I. Allec

Citrine Informatics (United States)

Sandro Scandolo

The Abdus Salam International Centre for Theoretical Physics (ICTP)

Cooperative Institutions

Pacific Northwest National Laboratory

Battelle

Richland College

Environmental Molecular Sciences Laboratory

Government of the United States of America

Physical Sciences (United States)

Washington State University

The Abdus Salam International Centre for Theoretical Physics (ICTP)

Scuola Internazionale Superiore di Studi Avanzati

AREA Science Park

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Cover Feature: Molecular‐Level Overhaul of γ‐Aminopropyl Aminosilicone/Triethylene Glycol Post‐Combustion CO 2 ‐Capture Solvents (ChemSusChem 13/2020)

ChemSusChem (2020)

David C. Cantu Deepika Malhotra Manh‐Thuong Nguyen Phillip Koech Difan Zhang

The Cover Feature illustrates the approach that bridges the fundamental aspects of atomistic simulations with the design of single-components diamines for CO2 capture. The image was designed by Cortland Johnson and Vassiliki-Alexandra Glezakou of PNNL. More information can be found in the Full Paper by D. C. Cantu et al. on page 3429 in Issue 13, 2020 (DOI: 10.1002/cssc.202000724).

Triethylene glycol

Feature (linguistics)

Feature film

10.1002/cssc.202001474

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Citations (0)

Atomic scale understanding of organic anion separations using ion-exchange resins

Journal of Membrane Science (2020)

Difan Zhang Pradeep Kumar Gurunathan Lauren Valentino Yupo J. Lin Roger Rousseau

Carboxylate

Ion-exchange resin

10.1016/j.memsci.2020.118890

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Citations (7)

Phase Stability and Broken-Symmetry Transition of Elemental Lithium up to 140 GPa

ChemPhysChem (2005)

Roger Rousseau Kentaro Uehara D. D. Klug John S. Tse

Structural Stability

10.1002/cphc.200500117

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Citations (42)

Synthesizing Clean Transportation Fuels from CO₂ Will at Least Quintuple the Demand for Non-carbogenic Electricity in the United States

Energy & Fuels (2020)

Johnathan E. Holladay Jonathan L. Male Roger Rousseau Robert S. Weber

We review alternatives that have been proposed to mitigate greenhouse gas (GHG) emissions from vehicles by comparing alternatives for displacing the current suite of transportation fuels to more GHG-sparing fuels and, to a lesser extent, powertrains. Two topical approaches, biofuels and electrofuels, appear to be less effective than direct electrification of the fleet. By biofuel, we mean a fuel derived from sustainably sourced biomass or waste carbon streams. By electrofuel, we mean a fuel derived from a carbon source in which most of the stored energy stems from an electrochemical conversion. For any direct electrification (e.g., battery-powered vehicle) or indirect electrification (e.g., electrofuel) technology to significantly reduce the overall emissions of carbon dioxide and criteria pollutants from the transportation sector, the grid would need to be modernized and decarbonized.

10.1021/acs.energyfuels.0c02595

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On the Role of Enthalpic and Entropic Contributions to the Conformational Free Energy Landscape of MIL‐101(Cr) Secondary Building Units

Advanced Theory and Simulations (2020)

Loukas Kollias David C. Cantu Vassiliki‐Alexandra Glezakou Roger Rousseau Matteo Salvalaglio

Abstract The thermo‐structural behavior of metal‐organic framework (MOF) precursors is responsible for regulating the introduction of defects in MOF structures during synthesis. In this paper, factors affecting the flexibility of MIL‐101(Cr) half‐secondary building units (half‐SBUs) are evaluated in solution using enhanced sampling methods. In particular, entropic and enthalpic contributions to the conformational free energy landscape of isolated MIL‐101(Cr) half‐SBUs are calculated in water, in the presence and absence of ionic species (Na + and F − ), and in N , N ‐dimethylformamide (DMF). This analysis leads to the observation that the interplay between enthalpy and entropy determines the most probable conformational state for half‐SBUs. This observation extends to the most relevant SBU intermediate, in which conformational entropy plays a key role in stabilizing configurations that differ from those found in the MIL‐101(Cr) crystal structure. The findings highlight the importance of explicitly considering entropic effects, associated with finite‐temperature sampling when estimating the relative stability of different conformers of SBUs.

SBus

Conformational isomerism

Energy landscape

Conformational entropy

10.1002/adts.202000092

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Citations (15)

Confinement effects and acid strength in zeolites

Nature Communications (2021)

Emanuele Grifoni GiovanniMaria Piccini Johannes A. Lercher Vassiliki‐Alexandra Glezakou Roger Rousseau

Abstract Chemical reactivity and sorption in zeolites are coupled to confinement and—to a lesser extent—to the acid strength of Brønsted acid sites (BAS). In presence of water the zeolite Brønsted acid sites eventually convert into hydronium ions. The gradual transition from zeolite Brønsted acid sites to hydronium ions in zeolites of varying pore size is examined by ab initio molecular dynamics combined with enhanced sampling based on Well-Tempered Metadynamics and a recently developed set of collective variables. While at low water content (1–2 water/BAS) the acidic protons prefer to be shared between zeolites and water, higher water contents ( n > 2) invariably lead to solvation of the protons within a localized water cluster adjacent to the BAS. At low water loadings the standard free energy of the formed complexes is dominated by enthalpy and is associated with the acid strength of the BAS and the space around the site. Conversely, the entropy increases linearly with the concentration of waters in the pores, favors proton solvation and is independent of the pore size/shape.

Hydronium

Metadynamics

Brønsted–Lowry acid–base theory

Acid strength

10.1038/s41467-021-22936-0

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Citations (127)

Reinventing Design Principles for Developing Low‐Viscosity Carbon Dioxide‐Binding Organic Liquids for Flue Gas Clean Up

ChemSusChem (2016)

Deepika Malhotra Phillip Koech David J. Heldebrant David C. Cantu Feng Zheng

Anthropogenic CO2 emissions from point sources (e.g., coal fired-power plants) account for the majority of the greenhouse gases in the atmosphere. Water-lean solvent systems such as CO2 -binding organic liquids (CO2 BOLs) are being developed to reduce the energy requirement for CO2 capture. Many water-lean solvents such as CO2 BOLs are currently limited by the high viscosities of concentrated electrolyte solvents, thus many of these solvents have yet to move toward commercialization. Conventional standard trial-and-error approaches for viscosity reduction, while effective, are time consuming and economically expensive. We rethink the metrics and design principles of low-viscosity CO2 -capture solvents using a combined synthesis and computational modeling approach. We critically study the effects of viscosity reducing factors such as orientation of hydrogen bonding, introduction of higher degrees of freedom, and cation or anion charge solvation, and assess whether or how each factor affects viscosity of CO2 BOL CO2 capture solvents. Ultimately, we found that hydrogen bond orientation and strength is the predominant factor influencing the viscosity in CO2 BOL solvents. With this knowledge, a new CO2 BOL variant, 1-MEIPADM-2-BOL, was synthesized and tested, resulting in a solvent that is approximately 60 % less viscous at 25 mol % CO2 loading than our base compound 1-IPADM-2-BOL. The insights gained from the current study redefine the fundamental concepts and understanding of what influences viscosity in concentrated organic CO2 -capture solvents.

10.1002/cssc.201601622

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Citations (32)

Dynamic formation of single-atom catalytic active sites on ceria-supported gold nanoparticles

Nature Communications (2015)

Yang‐Gang Wang Donghai Mei Vassiliki‐Alexandra Glezakou Jun Li Roger Rousseau

Abstract Catalysis by gold supported on reducible oxides has been extensively studied, yet issues such as the nature of the catalytic site and the role of the reducible support remain fiercely debated topics. Here we present ab initio molecular dynamics simulations of an unprecedented dynamic single-atom catalytic mechanism for the oxidation of carbon monoxide by ceria-supported gold clusters. The reported dynamic single-atom catalytic mechanism results from the ability of the gold cation to strongly couple with the redox properties of the ceria in a synergistic manner, thereby lowering the energy of redox reactions. The gold cation can break away from the gold nanoparticle to catalyse carbon monoxide oxidation, adjacent to the metal/oxide interface and subsequently reintegrate back into the nanoparticle after the reaction is completed. Our study highlights the importance of the dynamic creation of active sites under reaction conditions and their essential role in catalysis.

10.1038/ncomms7511

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Citations (443)

Finite-Temperature Effects on the Stability and Infrared Spectra of HCl(H₂O)₆ Clusters

The Journal of Physical Chemistry A (2007)

U. F. T. Ndongmouo Mal‐Soon Lee Roger Rousseau Francesca Baletto Sandro Scandolo

Theoretical studies of the interaction of HCl with small water clusters have so far neglected the effect of temperature, which ranges from a few tens of kelvin in cluster experiments, up to about 250 K in typical atmospheric conditions. We study the dynamical behavior of a selected set of HCl(H2O)6 clusters, representative of undissociated and dissociated configurations, by means of DFT-based first principles molecular dynamics. We find that the thermodynamcal stability of different configurations can be affected by temperature. We also present the infrared spectra of dissociated and undissociated configurations at 200 K and discuss the origin of the spectral features.

10.1021/jp0765603

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Citations (32)

Impeding 99Tc(IV) mobility in novel waste forms

Nature Communications (2016)

Mal‐Soon Lee Wooyong Um Guohui Wang Albert A. Kruger Wayne W. Lukens

Technetium ((99)Tc) is an abundant, long-lived radioactive fission product whose mobility in the subsurface is largely governed by its oxidation state. Tc immobilization is crucial for radioactive waste management and environmental remediation. Tc(IV) incorporation in spinels has been proposed as a novel method to increase Tc retention in glass waste forms during vitrification. However, experiments under high-temperature and oxic conditions show reoxidation of Tc(IV) to volatile pertechnetate, Tc(VII). Here we examine this problem with ab initio molecular dynamics simulations and propose that, at elevated temperatures, doping with first row transition metal can significantly enhance Tc retention in magnetite in the order Co>Zn>Ni. Experiments with doped spinels at 700 °C provide quantitative confirmation of the theoretical predictions in the same order. This work highlights the power of modern, state-of-the-art simulations to provide essential insights and generate theory-inspired design criteria of complex materials at elevated temperatures.

Vitrification

Nuclear fission product

Oxidation state

10.1038/ncomms12067

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Citations (130)