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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Enhanced Electrocatalytic Hydrogen Evolution Activity in Single-Atom Pt-Decorated VS 2 Nanosheets

Enhancing catalytic activity by decorating noble metals in catalysts provides an opportunity for promoting the electrocatalytic hydrogen evolution reaction (HER) application. However, there are few systematic studies on regulating the structures of noble metals in catalytic materials and investigating their influence on HER. Herein, Pt catalysts with different structures including single atoms (SAs), clusters, and nanoparticles well-controllably anchored on VS 2 nanosheets through a cost-effective optothermal method are reported, and their HER performance is studied. The most efficient Pt-decorated VS 2 catalyst (with both Pt SAs and clusters) delivers an overpotential of 77 mV at 10 mA cm –2 , close to that of Pt/C (48 mV). However, the optimal mass activity of Pt (normalizing to Pt content) is obtained from only SA Pt-decorated VS 2 (i.e., 22.88 A mg Pt –1 at 200 mV) and is 12 times greater than that of the Pt/C (1.87 A mg Pt –1 ), attributed to the greatly enhanced Pt utilization. Additionally, the theoretical simulations reveal that Pt SA decoration makes the adsorption free energy of H* closer to the thermoneutral value and improves the charge-transfer kinetics, significantly enhancing HER activity. Furthermore, this work offers a pathway to prepare the desired catalyst based on synergy of Pt structures and VS 2 and reveals the intrinsic mechanism for enhancing catalytic activity, which is important for HER applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Origin of medium-range atomic correlation in simple liquids: Density wave theory

The atomic pair-distribution function of simple liquid and glass shows exponentially decaying oscillations beyond the first peak, representing the medium-range order (MRO). The structural coherence length that characterizes the exponential decay increases with decreasing temperature and freezes at the glass transition. Conventionally, the structure of liquid and glass is elucidated by focusing on a center atom and its neighboring atom shell characterized by the short-range order (SRO) and describing the global structure in terms of overlapping local clusters of atoms as building units. However, this local bottom-up approach fails to explain the strong drive to form the MRO, which is different in nature from the SRO. We propose to add an alternative top-down approach based upon the density wave theory. In this approach, one starts with a high-density gas state and seeks to minimize the global potential energy in reciprocal space through density waves using the pseudopotential. The local bottom-up and global top-down driving forces are not mutually compatible, and the competition and compromise between them result in a final structure with the MRO. This even-handed approach provides a more intuitive explanation of the structure of simple liquid and glass.

42 ENGINEERING↗
DOE OSTI2022

Mean-field model for the Curie-Weiss temperature dependence of coherence length in metallic liquids

The coherence length of the medium-range order (MRO) in metallic liquids is known to display a Curie-Weiss temperature dependence; its inverse is linearly related to temperature, and when extrapolated from temperatures above the glass transition, the coherence length diverges at a negative temperature with a critical exponent of unity. We propose a mean-field pseudospin model that explains this behavior. Specifically, we model the atoms and their local environment as Ising spins with antiferromagnetic exchange interactions. We further superimpose an exchange interaction between dynamical heterogeneities, or clusters of atoms undergoing cooperative motion. The coherence length in the metallic liquid is thus the correlation length between dynamical heterogeneities. Overall, our results reaffirm the idea that the MRO coherence length is a measure of point-to-set correlations, and that local frustrations in the interatomic interactions are prominent in metallic liquids.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Superatoms as Superior Catalysts: ZrO versus Pd

Abstract Single‐atom catalysts are the focus of studies for over a decade due to their enhanced reactivity at smaller sizes. However, they have limitations as they offer only one active site, which may not be sufficient for reactions requiring the co‐adsorption of multiple reactants. Additionally, atoms can migrate on a substrate and coalesce, resulting in decreased reactivity. Here, an alternate path, a single‐superatom catalyst is provided. Superatoms are clusters of atoms that mimic the chemistry of atoms even if they do not contain a single atom whose chemistry they mimic. Motivated by an experimental paper on the photoelectron‐spectroscopy of negatively charged ions where ZrO is found to mimic properties of a Pd atom, first the reaction of Pd and ZrO with small molecules in the gas‐phase is studied and found that ZrO not only mimics the chemistry of Pd, but is able to activate these molecules more strongly than Pd. A detailed first‐principles study of CO 2 reduction (CO 2 ‐RR) and hydrogen evolution reactions (HER) on Pd and ZrO supported on graphene, Au(111), and Cu(111) surfaces shows that superatoms are indeed superior catalysts. The ability to design numerous superatoms by varying size and composition offers a promising new paradigm for catalyst design and synthesis.

Chemistry↗
DOE OSTI2023

Activating Bi p- orbitals in Dispersed Clusters of Amorphous BiO x for Electrocatalytic Nitrogen Reduction

Catalytic strategies based on main group metals are significantly less advanced than those of transition metal catalysis, leaving untapped areas of potentially fruitful research. Here, in this study, we demonstrate an effective approach for the modulation of Bi 6p energy levels during the construction of atomically dispersed clusters of amorphous BiO x . Bi oxidation state is proposed to strongly affects the nitrogen fixation activity, with the half-occupied p z orbitals of the Bi 2+ ions being highly efficient toward electron injection into the inert N 2 molecule. With sufficient catalytic sites to adsorb and activate N 2 , the bonding between N 2 and catalyst is able to be in situ identified. The catalyst shows an outstanding Faraday efficiency (≈30 %) and high yield (≈113 μg h -1 mg -1 cat ) in NH 3 production, outperforming most of the existing catalysts in aqueous solution. These results lay the basis for developing the potential of p-block elements for catalysis of multi-electron reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Achieving Higher Activity of Acidic Oxygen Evolution Reaction Using an Atomically Thin Layer of IrO x over Co 3 O 4

The development of electrocatalysts with reduced iridium (Ir) loading for the oxygen evolution reaction (OER) is essential to produce low-cost green hydrogen from water electrolysis under acidic conditions. Herein, an atomically thin layer of iridium oxide (IrO x ) has been uniformly dispersed onto cobalt oxide (Co 3 O 4 ) nanocrystals to improve the efficient use of Ir for acidic OER. In situ characterization and theoretical calculations reveal that compared to the conventional IrOx cluster, the atomically thin layer of IrO x shows stronger interaction with the Co 3 O 4 and consequently higher OER activity due to the Ir-O-Co bond formation at the interface. Equally important, the facile synthetic method and the promising activity in the proton exchange membrane water electrolyzer, reaching 1 A cm -2 at 1.7 V with remarkable durability, enable potential scale-up applications. In conclusion, these findings provide a mechanistic understanding for designing active, stable and lower-cost electrocatalysts with well-defined structures for acidic OER.

58 GEOSCIENCES↗
DOE OSTI2024

Cu site differentiation in tetracopper(I) sulfide clusters enables biomimetic N 2 O reduction

Copper clusters feature prominently in both metalloenzymes and synthetic nanoclusters that mediate catalytic redox transformations of gaseous small molecules. Such reactions are critical to biological energy conversion and are expected to be crucial parts of renewable energy economies. However, the precise roles of individual metal atoms within clusters are difficult to elucidate, particularly for cluster systems that are dynamic under operating conditions. Here, we present a metal site-specific analysis of synthetic Cu 4 (μ 4 -S) clusters that mimic the Cu Z active site of the nitrous oxide reductase enzyme. Leveraging the ability to obtain structural snapshots of both inactive and active forms of the synthetic model system, we analyzed both states using resonant X-ray diffraction anomalous fine structure (DAFS), a technique that enables X-ray absorption profiles of individual metal sites within a cluster to be extracted independently. Using DAFS, we found that a change in cluster geometry between the inactive and active states is correlated to Cu site differentiation that is presumably required for efficient activation of N 2 O gas. More precisely, we hypothesize that the Cu δ+ ∙∙∙Cu δ- pairs produced upon site differentiation are poised for N 2 O activation, as supported by computational modeling. These results provide an unprecedented level of detail on the roles of individual metal sites within the synthetic cluster system and how those roles interplay with cluster geometry to impact the reactivity function. We expect this fundamental knowledge to inform understanding of metal clusters in settings ranging from (bio)molecular to nanocluster to extended solid systems involved in energy conversion.

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

Design of Dilute Palladium–Indium Alloy Catalysts for the Selective Hydrogenation of CO 2 to Methanol

Adding small amounts of a more reactive dopant metal to a more selective host metal is a well-known strategy for promoting the catalytic reactivity of the latter without sacrificing its selectivity. While substantial attention has been given to coinage metal hosts for activating individual C–H or O–H bonds, less attention has been given to more exotic metals, such as indium, which is highly selective in the complex hydrogenation of CO 2 to methanol. Herein, we describe the synthesis and properties of Pd–In alloys containing Pd in various states of aggregation (isolated atom, small clusters, and extended clusters) assessed through various characterization methods. These materials exhibit unique catalytic behaviors, with Pd promoting both the reaction rate and methanol selectivity in all cases, though its efficacy is highest when Pd is present in small clusters. Here, the inefficiency of high Pd loadings is due in part to losses in Pd accessibility, while the importance of aggregated vs isolated Pd is theorized to result from accelerated H 2 activation. Methods used to synthesize more conventional dilute-limit and single-atom alloy catalysts can, therefore, be extended to non-coinage metal hosts to promote and control more complex chemistries, though the roles of ensemble size may greatly differ.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Utilizing Single-Crystalline Transformations for Precise Atom Placement in Multicomponent Cluster-Based Coordination Networks

The assembly of cluster or superatom building-blocks into extended solids has revolutionized materials design, enabling the synthesis of modular semiconductors with well-defined structures and tunable electronic, magnetic or optical properties. This strategy has recently advanced the synthesis of complex metal oxides with multifunctional or emergent behaviors, but precise atom placement of multiple elements with similar chemistries or preferred coordination environments remains a significant challenge. Here, in this study, we present a strategy for synthesizing polyoxometalate (POM)-based coordination networks with up to three different cations in precisely defined positions. Our approach leverages a single-crystal-to-single-crystal (SCSC) transformation in which the spatial placement of cations is governed by their availability at distinct stages of crystallization and transformation. Specifically, [ZP 5 W 30 O 110 ] (15-n)- (Z = Na + , K + , Ca 2+ , Ag + , Bi 3+ , Y 3+ , any Ln 3+ , Th 4+ ) is coordinatively assembled with various bridging metal cations (Y 3+ , any Ln 3+ , Th 4+ ). By using the encapsulated cation (Z) to "label" the POM, we track the phase-transformation and confirm the retention of single crystallinity. The integrated use of POM labeling and SCSC transformation enables rational control over cation distribution and establishes a versatile strategy for constructing multicomponent materials with high compositional and spatial precision.

Chen, Linfeng [Univ. of California, San Diego, CA ↗
DOE OSTI2020

Highly Durable and Active Pt/Sb-Doped SnO 2 Oxygen Reduction Reaction Electrocatalysts Produced by Atomic Layer Deposition

Platinum supported on mixed-metal oxides (MMOs) are a class of active and durable cathode catalysts for proton exchange membrane fuel cell (PEMFC) due to a combination of the high oxidative stability of the supports and strong-metal-support interactions (SMSI) that enable them to exceed the activity of Pt/C. Herein, we solve a significant remaining challenge with Pt/MMO systems, namely the relatively low surface area and porosity. This is achieved by dispersing nearly-uniform Pt clusters using atomic layer deposition (ALD) on highly conductive (6.2 S/cm) and stable antimony doped tin dioxide (ATO) support. ALD-Pt/ATO exhibited significantly higher electrochemically active surface area (ECSA) (74 m 2 /g) and oxygen reduction reaction (ORR) catalytic activity (102 mA/mg Pt at 0.9 V vs. RHE) compared to Pt/ATO synthesized using ethylene glycol (ECSA=31 m 2 /g Pt , mass activity=52 mA/mg Pt at 0.9 V vs. RHE) and formic acid reduction methods (ECSA=28 m 2 /g Pt , mass activity=46 mA/mg Pt at 0.9 V vs. RHE). Further characterization showed that wet chemical methods resulted in poorer Pt particle dispersion, poor control over Pt particle size distribution and chemical degradation of the support (during Pt deposition). Given the near-ideal Pt particle size distribution of the ALD-Pt/ATO, particle size growth and loss of ECSA was found to be minimal over the course of rigorous potential cycling. Thus, after 10,000 potential cycles between 1V and 1.5V vs. RHE, ALD-Pt/ATO and other Pt/ATOs were found to retain 100% of their initial ECSA compared to 57.6% retention for Pt/C. Upon testing in a H 2 /air PEMFC, following 1,000 potential cycles, the change in ALD-Pt/ATO performance was negligible while Pt/C exhibited a 68.2% loss of initial peak power density. Thus, ALD-Pt/ATO is an active and highly durable ORR electrocatalyst in PEMFCs under start-up-shut down conditions.

25 ENERGY STORAGE↗
DOE OSTI2021

Sulfur-doped graphene anchoring of ultrafine Au 25 nanoclusters for electrocatalysis

The biggest challenge of exploring the catalytic properties of under-coordinated nanoclusters is the issue of stability. We demonstrate herein that chemical dopants on sulfur-doped graphene (S-G) can be utilized to stabilize ultrafine (sub-2 nm) Au 25 (PET)18 clusters to enable stable nitrogen reduction reaction (NRR) without significant structural degradation. The Au 25 @S-G exhibits an ammonia yield rate of 27.5μgNH 3 ∙ mg Au -1 ∙ h -1 at -0.5 V with faradic efficiency of 2.3%. More importantly, the anchored clusters preserve ~ 80% NRR activity after four days of continuous operation, a significant improvement over the 15% remaining ammonia production rate for clusters loaded on undoped graphene tested under the same conditions. Isotope labeling experiments confirmed the ammonia was a direct reaction product of N 2 feeding gas instead of other chemical contaminations. Ex-situ X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy of post-reaction catalysts reveal that the sulfur dopant plays a critical role in stabilizing the chemical state and coordination environment of Au atoms in clusters. Further ReaxFF molecular dynamics (RMD) simulation confirmed the strong interaction between Au nanoclusters (NCs) and S-G. Furthermore, this substrate-anchoring process could serve as an effective strategy to study ultrafine nanoclusters’ electrocatalytic behavior while minimizing the destruction of the under-coordinated surface motif under harsh electrochemical reaction conditions.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Metallofullerene photoswitches driven by photoinduced fullerene-to-metal electron transfer

We report on the discovery and detailed exploration of the unconventional photo-switching mechanism in metallofullerenes, in which the energy of the photon absorbed by the carbon cage π-system is transformed to mechanical motion of the endohedral cluster accompanied by accumulation of spin density on the metal atoms. Comprehensive photophysical and electron paramagnetic resonance (EPR) studies augmented by theoretical modelling are performed to address the phenomenon of the light-induced photo-switching and triplet state spin dynamics in a series of Y x Sc 3-x N@C 80 (x = 0–3) nitride clusterfullerenes. Variable temperature and time-resolved photoluminescence studies revealed a strong dependence of their photophysical properties on the number of Sc atoms in the cluster. All molecules in the series exhibit temperature-dependent luminescence assigned to the near-infrared thermally-activated delayed fluorescence (TADF) and phosphorescence. The emission wavelengths and Stokes shift increase systematically with the number of Sc atoms in the endohedral cluster, whereas the triplet state lifetime and S 1 –T 1 gap decrease in this row. For Sc 3 N@C 80 , we also applied photoelectron spectroscopy to obtain the triplet state energy as well as the electron affinity. Spin distribution and dynamics in the triplet states are then studied by light-induced pulsed EPR and ENDOR spectroscopies. The spin–lattice relaxation times and triplet state lifetimes are determined from the temporal evolution of the electron spin echo after the laser pulse. Well resolved ENDOR spectra of triplets with a rich structure caused by the hyperfine and quadrupolar interactions with 14 N, 45 Sc, and 89 Y nuclear spins are obtained. The systematic increase of the metal contribution to the triplet spin density from Y 3 N to Sc 3 N found in the ENDOR study points to a substantial fullerene-to-metal charge transfer in the excited state. These experimental results are rationalized with the help of ground-state and time-dependent DFT calculations, which revealed a substantial variation of the endohedral cluster position in the photoexcited states driven by the predisposition of Sc atoms to maximize their spin population.

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

Memory-dictated dynamics of single-atom Pt on CeO2 for CO oxidation

Abstract Single atoms of platinum group metals on CeO 2 represent a potential approach to lower precious metal requirements for automobile exhaust treatment catalysts. Here we show the dynamic evolution of two types of single-atom Pt (Pt 1 ) on CeO 2 , i.e., adsorbed Pt 1 in Pt/CeO 2 and square planar Pt 1 in Pt AT CeO 2 , fabricated at 500 °C and by atom-trapping method at 800 °C, respectively. Adsorbed Pt 1 in Pt/CeO 2 is mobile with the in situ formation of few-atom Pt clusters during CO oxidation, contributing to high reactivity with near-zero reaction order in CO. In contrast, square planar Pt 1 in Pt AT CeO 2 is strongly anchored to the support during CO oxidation leading to relatively low reactivity with a positive reaction order in CO. Reduction of both Pt/CeO 2 and Pt AT CeO 2 in CO transforms Pt 1 to Pt nanoparticles. However, both catalysts retain the memory of their initial Pt 1 state after reoxidative treatments, which illustrates the importance of the initial single-atom structure in practical applications.

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

Photodissociation and Theory to Investigate Uranium Oxide Cluster Cations

Uranium oxide cluster cations of the form U n O m + are produced by laser vaporization of a depleted uranium rod in a pulsed supersonic expansion. Ions are mass-analyzed and mass-selected with a time-of-flight spectrometer and studied with UV laser multiphoton dissociation. Cations of the stoichiometry UO 2 (UO 3 ) n + were observed as photofragments from all photodissociated cluster cations. (UO 3 ) n + clusters were also observed to result from dissociation of larger (UO 3 ) n + clusters, with UO 3 neutral as a common leaving group. Electronic structure calculations were used to investigate the stability of the prominent uranium oxide cluster cations using density functional theory (DFT) with the hybrid B3LYP exchange-correlation functional and at the CCSD(T) level and cc-pVnZ-PP basis sets (n = D,T), including diffuse orbitals as computational expense and availability permitted. Clustering energies, relative energies and dissociation energies of the cations are reported. The lowest energy neutral (UO 3 ) n clusters up to n = 3 are rings, n = 4 and 5 are chains with very low energy rings, and n = 6 is 3D. Finally, the lowest energy structures for UO 2 (UO 3 ) n + are composed of uranyl-like UO 2 + units bound by bridging oxygens to other UO 2 2+ units for n = 2 and 3, and for n = 4 a more complex 3D structure is predicted.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Resistivity distribution and donor properties of antimony-doped n -type Czochralski silicon ingots

We investigate antimony (Sb)-doped Czochralski-grown silicon as an alternative n-type substrate for photovoltaic applications, and characterize their axial resistivity distribution, donor properties, and mechanical strength. We find that Sb-doped ingots can achieve a more uniform resistivity distribution along the axial direction compared to P-doped counterparts. Dopant concentration profiles in P-doped ingots can be accurately modelled using the standard Scheil's equation, accounting only for dopant segregation during solidification. In contrast, modelling Sb-doped ingots requires consideration of both dopant segregation and evaporation effects to fit the dopant distribution accurately. Using electron paramagnetic resonance spectroscopy at 9 K, we observe two hyperfine lines in P-doped samples, and six hyperfine lines for Sb 121 and eight for Sb 123 isotopes, with the number of hyperfine lines governed by the nuclear spins. We further identify two-atom Sb clustering in the Sb-doped wafers, confirmed through simulations of the additional weak electron paramagnetic resonance peaks. Finally, we find that 140 μm as-cut planar Sb-doped wafers exhibit slightly higher mechanical strength compared to P-doped wafers.

14 SOLAR ENERGY↗
DOE OSTI2020

Crystal Structure and Atomic Vacancy Optimized Thermoelectric Properties in Gadolinium Selenides

Thermoelectric materials enable the energy conversion of waste heat into electricity, helpful to relieve global energy crisis. Here, we report a systematic investigation on high-temperature thermoelectric gadolinium selenides, cubic Gd 3-x Se 4 (x = 0.16, 0.21 and 0.25) and orthorhombic Gd 2 Se 3-y (y = 0.02, 0.06 and 0.08). High energy synchrotron x-ray diffraction and total scattering have been used to investigate the crystallographic and local structures. Atomic-scale clusters of Gd vacancy in the cubic phase are observed by employing the reverse Monte Carlo simulation. For cubic Gd 3-x Se 4 , adjusting Gd vacancy triggers the effect of multiple conduction bands, confirmed by the increase in effective masses and theoretical calculations. A reasonable peak zT value of 0.27 is achieved at 850 K for Gd 3-x Se 4 (x = 0.16). On the other hand, tuning Se vacancy enables the optimization of electron concentration for the orthorhombic Gd 2 Se 3-y . More significantly, its low deformation potential (Ξ = 12eV) gives rise to enhanced electron mobility and higher peak zT value of 0.54 at 850 K for Gd 2 Se 3-y (y = 0.02). Intriguingly, a higher zT of 1.2 at 1200 K is reasonably predicted by quality factor analysis. Finally, this work extends the scope of high-temperature thermoelectric materials and facilitates the exploration of novel high-temperature thermoelectric materials

36 MATERIALS SCIENCE↗
DOE OSTI2025

Ligand-Driven Electrochemical Tuning of Co 6 Se 8 Chevrel Clusters

Molecular “Chevrel-type” clusters of the formula Co 6 Se 8 L 6 (L = neutral ligand) are a well-studied class of clusters due to their utility as molecular analogues to the Chevrel extended solid phase and their application as subunits in hierarchical materials. However, their solution and optical properties remain relatively underexplored. Aiming to develop the fundamental relationships between the molecular and electronic structures of these clusters and their electrochemical and photophysical properties, this work reports the preparation of a series of Co 6 Se 8 (P­(C 6 H 4 R) 3 ) 6 -type clusters with R = Cl (1), F (2), H (3), CH 3 (4), and OCH 3 (5) via a stepwise synthetic approach. Solution and solid-state experimental characterization and density functional theory calculations reveal that the Co 6 Se 8 cores of 1–5 maintain consistent electronic and structural properties despite the variation of the triarylphosphine ligand para-substituent Hammett parameters (σ p ). However, cyclic voltammetry measurements indicate that the electron transfer energetics of 1–5 are strongly influenced by ligand substitution, with the E 1/2 of a given redox event spanning ∼0.5 V depending on the triarylphosphine ligand’s σ p . In conclusion, these findings support the characterization of Co 6 Se 8 clusters as atomically precise nanoclusters with both the structural robustness and the electrochemical tunability needed to act as components in larger charge transfer assemblies.

Wheaton, Amelia M. [Argonne National Laboratory (A↗
DOE OSTI2023

Permutationally Invariant Networks for Enhanced Sampling (PINES): Discovery of Multimolecular and Solvent-Inclusive Collective Variables

The typically rugged nature of molecular free energy landscapes can frustrate efficient sampling of the thermodynamically relevant phase space due to the presence of high free energy barriers. Enhanced sampling techniques can improve phase space exploration by accelerating sampling along particular collective variables (CVs). A number of techniques exist for data-driven discovery of CVs parameterizing the important large scale motions of the system. A challenge to CV discovery is learning CVs invariant to symmetries of the molecular system, frequently rigid translation, rigid rotation, and permutational relabeling of identical particles. Of these, permutational invariance has proved a persistent challenge in frustrating the data-driven discovery of multi-molecular CVs in systems of self-assembling particles and solvent-inclusive CVs for solvated systems. In this work, we integrate Permutation Invariant Vector (PIV) featurizations with autoencoding neural networks to learn nonlinear CVs invariant to translation, rotation, and permutation, and perform interleaved rounds of CV discovery and enhanced sampling to iteratively expand sampling of configurational phase space and obtain converged CVs and free energy landscapes. Here, we demonstrate the Permutationally Invariant Network for Enhanced Sampling (PINES) approach in applications to the self-assembly of a 13-atom Argon cluster, association/dissociation of a NaCl ion pair in water, and hydrophobic collapse of a C 45 H 92 n-pentatetracontane polymer chain. We make the approach freely available as a new module within the PLUMED2 enhanced sampling libraries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗