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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

A DFT analysis of the ground and charge-transfer excited states of Sc 3 N@I h –C 80 fullerene coupled with metal-free and zinc-phthalocyanine

Endohedral metallofullerenes and phthalocyanine derivatives are recognized as excellent active materials in organic photovoltaics (OPVs). The tri-metallic nitride endohedral C 80 fullerenes have greater absorption coefficients in the visible region and electron-accepting abilities similar to C 60 , which can allow for higher efficiencies in OPV devices. Here, we have investigated the ground and charge transfer excited states of two co-facial donor–acceptor (D–A) molecular conjugates formed by the non-covalent coupling of trimetallic nitride endohedral fullerene (Sc 3 N@I h –C 80 ) with metal-free (H 2 Pc) and zinc-phthalocyanine (ZnPc) chromophores using DFT calculations. The charge transfer (CT) excitation energies are calculated using the perturbative delta-SCF method that enforces orthogonality between the ground and excited states. The binding energies calculated using the PBE and DFT-D3 methods indicate that the dispersion effects play an important role in the stabilization of these complexes. The ground state dipole moment of the Sc 3 N@C 80 –H 2 Pc dyad is much larger than that of Sc 3 N@C 80 –ZnPc, but this is reversed in the excited state where the dipole moment of Sc 3 N@C 80 –ZnPc increases significantly. The lowest few excitation energies in the gas phase for the two complexes are very close, in the range of 1.51–2.66 eV for Sc 3 N@C 80 –ZnPc and 1.51–2.71 eV for the Sc 3 N@C 80 –H 2 Pc complex. However, the lower ionization potential and lower exciton binding energy make the Sc 3 N@C 80 –ZnPc dyad a better candidate for OPVs as compared to the Sc 3 N@C 80 –H 2 Pc dyad.

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

Adsorption Study of Al 3+ , Cr 3+ , and Mn 2+ onto Quartz and Corundum using Flow Microcalorimetry, Quartz Crystal Microbalance, and Density Functional Theory

The adsorption of aqueous ions onto natural mineral surfaces controls numerous mineral–water interactions and is governed by, among other numerous factors, ion dehydration and hydrolysis. This work explored the extent to which dehydration and hydrolysis affect the adsorption of three metal cations, Al 3+ , Cr 3+ , and Mn 2+ , onto quartz (SiO2) and corundum (Al 2 O 3 ) surfaces at pH 3.8 through the integration of flow microcalorimetry (FMC), quartz crystal microbalance with dissipation (QCM-D) measurements and density functional theory (DFT) calculations. At pH 3.8, negligible amounts of Mn 2+ and Al 3+ are hydrolyzed, while 78% of Cr 3+ exist in hydrolyzed species. QCM-D and FMC measurements showed that Al 3+ and Cr 3+ adsorb to both surfaces, while Mn 2+ adsorbed only to Al 2 O 3 . DFT bond energy calculations confirmed the favorable bonding between the mineral surfaces and Al 3+ and Cr 3+ , and that Mn 2+ adsorption onto SiO 2 was unfavorable. Furthermore, FMC showed that on both surfaces, the adsorption of Al 3+ was endothermic and reversible, while that of Cr 3+ was exothermic and partially irreversible. Through the integration of experimental and computational methods, this work suggested that the reversible adsorption of unhydrolyzed cations (Mn 2+ and Al 3+ ) occurred through weak electrostatic interactions. The large energy cost required to dehydrate unhydrolyzed cations resulted in an endothermic adsorption process. Meanwhile, hydrolyzed Cr 3+ species can adsorb on quartz and corundum through covalent-bond formation, and thus, their adsorption was partially irreversible. Furthermore, the hydrolysis of Cr 3+ lowered the dehydration energy during adsorption, resulting in an exothermic adsorption. By using bond energies as a guide to indicate the possibility of thermodynamically favored adsorption, there was a strong agreement between the DFT and experimental techniques. The findings presented here contribute to understanding and predicting various mineral–water interfacial processes in the natural environment.

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

Correct symmetry in density functional theory calculations of δ-Pu [Slides]

Density functional theory (DFT) calculations in the delta-phase of Pu have long relied on the antiferromagnetic (AFM) spin structure to approximate the material’s unique electronic structure. The resulting tetragonal distortion away from the correct cubic symmetry was believed to be a necessary consequence of allowing an ordered spin structure.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Milestone report: The simulation of radiation driven gas diffusion in UO 2 at low temperature

Below 1000 K it is thought that fission gas diffusion in nuclear fuel during irradiation occurs through atomic mixing due to radiation damage. This is an important process for nuclear reactor performance as it affects fission gas release, particularly from the periphery of the pellet where such temperatures are normal. Here we present a molecular dynamics study of Xe and Kr diffusion due to irradiation. Thermal spikes and cascades have been used to study the electronic stopping and ballistic phases of damage, respectively. Our results predict that O and Kr exhibit the greatest diffusivity and U the least, while Xe lies in between. It is concluded that the ballistic phase does not sufficiently account for the experimentally observed diffusion. Preliminary thermal spike calculations indicate that the electronic stopping phase generates greater fission gas displacement than the ballistic phase, although further calculation must be carried out to confirm this. A good description of the system by the empirical potentials is important over the very wide temperatures induced during thermal spike and damage cascade simulations. This has motivated the development of a parameter set for gas-actinide and gas-oxygen interactions that is complementary for use with a recent many-body potential set. A comprehensive set of density functional theory (DFT) calculations were used to study Xe and Kr incorporation at a number of sites in CeO 2 , ThO 2 , UO 2 and PuO 2 . These structures were used to fit a potential, which was used to generate molecular dynamics (MD) configurations incorporating Xe and Kr at 300 K, 1500 K, 3000 K and 5000 K. Subsequent matching to the forces predicted by DFT for these MD configurations was used to refine the potential set. This fitting approach ensured weighted fitting to configurations that are thermodynamically significant over a broad temperature range, while avoiding computationally expensive DFT-MD calculations. The resultant gas potentials were validated against DFT binding energies and are suitable for simulating combinations of Xe and Kr in solid solutions of CeO 2 , ThO 2 , UO 2 and PuO 2 , providing a powerful tool for the atomistic simulation of conventional nuclear reactor fuel UO 2 as well as advanced MOX fuels.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

Carbocation Stability in H-ZSM5 at High Temperature

Zeolites are common catalysts for multiple industrial applications, including alcohol dehydration to produce olefins, and given their commercial importance, reaction mechanisms in zeolites have long been proposed and studied. Some proposed reaction mechanisms for alcohol dehydration exhibit noncyclic carbocation intermediates or transition states that resemble carbocations, and several previous studies suggest that the tert-butyl cation is the only noncyclic cation more stable than the corresponding chemisorbed species with the hydrocarbon bound to the framework oxygen (i.e., an alkoxide). To determine if carbocations can exist at high temperatures in zeolites, where these catalysts are finding new applications for biomass vapor-phase upgrading (~500 °C), the stability of carbocations and the corresponding alkoxides were calculated with two ONIOM embedding methods (M06-2X/6-311G(d,p):M06-2X/3-21G) and (PBE-D3/6-311G(d,p):PBE-D3/3-21G) and plane-wave density functional theory (DFT) using the PBE functional corrected with entropic and Tkatchenko-Scheffler van der Waals corrections. The embedding methods tested are unreliable at finding minima for primary carbocations, and only secondary or higher carbocations can be described with embedding methods consistent with the periodic DFT results. The relative energy between the carbocations and alkoxides differs significantly between the embedding and the periodic DFT methods. The difference is between ~0.23 and 14.30 kcal/mol depending on the molecule, the model, and the functional chosen for the embedding method. At high temperatures, the pw-DFT calculations predict that the allyl, isopropyl, and sec-butyl cations exhibit negligible populations while acetyl and tertbutyl cations exhibit significant populations (>10%). Moreover, the periodic DFT results indicate that mechanisms including secondary and tertiary carbocations intermediates or carbocations stabilized by adjacent oxygen or double bonds are possible at high temperatures relevant to some industrial uses of zeolite catalysts, although as the minority species in most cases.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Fragility of Fermi arcs in Dirac semimetals

We use tunable, vacuum ultraviolet laser based angle-resolved photoemission spectroscopy and density functional theory (DFT) calculations to study the electronic properties of Dirac semimetal candidate cubic PtBi 2 . In addition to bulk electronic states we also find surface states in PtBi 2 , which is expected as PtBi 2 was theoretically predicated to be a candidate Dirac semimetal. The surface states are also well reproduced from DFT band calculations. Impressively, the topological surface states form Fermi contours rather than double Fermi arcs that were observed in Na 3 Bi. The surface bands forming the Fermi contours merge with bulk bands in proximity to the Dirac point projections, as expected. Our data validate the existence of Dirac states in PtBi 2 and reveal the fragility of the Fermi arcs in Dirac semimetals. Because the Fermi arcs are not topologically protected in general, they can be deformed into Fermi contours, as proposed by M. Kargarian et al. [Proc. Natl. Acad. Sci. USA 113, 8648 (2016)]. Our results demonstrate the validity of this theory in PtBi 2 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Density Functional Tight Binding Insights into Plasmonic Silver–Platinum Nanoparticles and Alloys for Enhanced Photocatalysis

Developing accurate and efficient Slater-Koster (SK) tight-binding parameter sets is essential for quantum plasmonic studies of alloyed metal nanoparticles, as conventional time dependent density functional theory (TD-DFT) calculations are computationally prohibitive for larger clusters. In this work, we develop and validate density functional tight binding (DFTB) parameter sets for both ground state (GS-SK) and excited state (ES-SK) calculations to study the structural, electronic, and optical properties of silver (Ag), platinum (Pt), and Ag–Pt nanoalloys. Our investigation of the ground state properties demonstrates that the GS-SK parameters enable DFTB to closely reproduce the electronic structures of platinum clusters with diverse sizes and geometries – showing qualitative agreement with DFT for density of states (DOS) profiles and energy levels. The ES-SK parameters accurately describe excited-state properties compared to TD-DFT reference calculations, including the broad, featureless absorption profiles of Pt that are dominated by interband transitions. Using the ES-SK parameters within a real-time TD-DFTB framework, we compute size-dependent optical absorption spectra of Ag, Pt and Ag-Pt nanocubes containing up to 1099 atoms (size ∼4.18 nm). A detailed study of Ag–Pt and Pt-Ag core–shell nanoparticles shows quenching of the Ag plasmon resonance even at monolayer coverage for Ag-Pt, but not for Pt-Ag. We also show how to define submonolayer Ag-core Pt-shell cubic structures that have similar optical properties to those generated experimentally for much larger particles, which offers potential for describing plasmon-enhanced photocatalysis. Collectively, the GS-SK and ES-SK parameter sets provide an accurate, computationally efficient approach for modeling the complex optical and electronic behavior of noble–transition metal nanostructures and their alloys.

SPR↗
DOE OSTI2015

A classical reactive potential for molecular clusters of sulphuric acid and water

We present a two state empirical valence bond (EVB) potential describing interactions between sulphuric acid and water molecules and designed to model proton transfer between them within a classical dynamical framework. The potential has been developed in order to study the properties of molecular clusters of these species, which are thought to be relevant to atmospheric aerosol nucleation. The particle swarm optimisation method has been used to fit the parameters of the EVB model to density functional theory (DFT) calculations. Features of the parametrised model and DFT data are compared and found to be in satisfactory agreement. In particular, it is found that a single sulphuric acid molecule will donate a proton when clustered with four water molecules at 300 K and that this threshold is temperature dependent. SMK was supported in part by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences; JLS and IJF were supported by the IMPACT scheme at University College London (UCL). We acknowledge the UCL Legion High Performance Computing Facility, and associated support services together with the resources of the National Energy Research Scientific Computing Center (NERSC), which is supported by the U.S. Department of Energy under Contract No. DE-AC02- 05CH11231. JLS thanks Dr. Gregory Schenter, Dr. Theo Kurtén and Prof. Hanna Vehkamäki for important guidance and discussions.

aerosols↗
DOE OSTI2023

VASP calculations on Chicoma: CPU vs. GPU [Slides]

Density functional theory (DFT) calculations with the VASP code provide insight into materials behavior. In particular, the behavior of Pu still poses challenges to our understanding. Calculations for a 108-atom system that represents delta phase Pu with one substitutional Ga show a significant speedup running on GPUs vs CPUs. The gain in speed (2.7), however, remains well below the ratio of SU per node hour conversions, 540/108 = 5.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Thermal properties of the metallic delafossite PdCo⁢O 2 : A combined experimental and first-principles study

Metallic delafossite materials (e.g., PdCo⁢O 2 , PtCo⁢O 2 ), have attracted much recent attention due to record-high oxide conductivities, the origins of which remain unclear. Relatively little attention has been paid to their related thermal properties, however. Here, we address this via wide temperature range experimental studies of the crystal structure, thermal expansion, and specific heat of single-crystal PdCo⁢O 2 , combined with density-functional theory (DFT) calculations of the electronic and phononic densities of states, and thus thermal properties. PdCo⁢O 2 is shown to retain the $R\bar{3}m$ space group from 12 to 1000 K, exhibiting a- and c-axis thermal expansion in good quantitative agreement with DFT-based lattice dynamics calculations. The Co-O bond lengths additionally elucidate the stability of the low-spin state of the nominally Co 3+ ions, which is a notable difference between the edge-shared Co-O octahedra in PdCo⁢O 2 and the corner-shared octahedra in Co-based perovskites. Measurements of specific heat from 1.9 to 400 K provide accurate values for the Debye temperature and Sommerfeld coefficient, the phononic part being describable via a combined Debye-Einstein approach (accounting for high-frequency oxygen-related optical phonons), with excess intermediate-temperature specific heat due to a prominent low-energy peak in the phonon density of states. Most significantly, all electronic and phononic contributions to the specific heat are shown to be remarkably closely reproduced by DFT-based calculations, establishing quantitative understanding of key thermal properties of the metallic delafossite PdCo⁢O 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2020

Developing single-site Pt catalysts for the preferential oxidation of CO: A surface science and first principles-guided approach

Here, we report a comprehensive study combining surface science, Density Functional Theory (DFT) calculations, and catalyst synthesis, characterization, and testing to investigate the preferential oxidation of CO in the presence of H 2 over single-site Pt 1 /Cu x O catalysts. Surface science studies show that while Pt 1 /Cu x O model surfaces enable low-temperature CO oxidation via a Mars-van Krevelen mechanism, there was no evidence for H 2 activation or oxidation. DFT-based calculations explain these results and demonstrate that the H 2 oxidation barrier is high as compared to H 2 desorption from Pt 1 /Cu x O. Inspired by these model catalyst studies, nanoporous Pt 1 /Cu x O catalysts were synthesized and demonstrated to be active and highly selective for the preferential oxidation of CO. This work highlights the potential of combined surface science, theory, and catalyst studies for identifying new catalytic materials, which in this case led to the development of a promising single-site Pt 1 /Cu x O catalyst for the preferential oxidation of CO.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

A First-Principles Study of the Structural and Thermo-Mechanical Properties of Tungsten-Based Plasma-Facing Materials

Tungsten (W) and tungsten alloys are being considered as leading candidates for structural and functional materials in future fusion energy devices. The most attractive properties of tungsten for the design of magnetic and inertial fusion energy reactors are its high melting point, high thermal conductivity, low sputtering yield, and low long-term disposal radioactive footprint. Despite these relevant features, there is a lack of understanding of how the structural and mechanical properties of W-based alloys are affected by the temperature in fusion power plants. In this work, we present a study on the thermo-mechanical properties of five W-based plasma-facing materials. First-principles density functional theory (DFT) calculations are combined with the quasi-harmonic approximation (QHA) theory to investigate the electronic, structural, mechanical, and thermal properties of these W-based alloys as a function of temperature. The coefficient of thermal expansion, temperature-dependent elastic constants, and several elastic parameters, including bulk and Young’s modulus, are calculated. Our work advances the understanding of the structural and thermo-mechanical behavior of W-based materials, thus providing insights into the design and selection of candidate plasma-facing materials in fusion energy devices.

42 ENGINEERING↗
DOE OSTI2017

Intermediate phases in sodium intercalation into MoS 2 nanosheets and their implications for sodium-ion batteries

Alkali metal ion intercalation into layered transition-metal dichalcogenide structures is a promising approach to make next generation rechargeable batteries for energy storage. It has been noted that the number of Na-ions which can be reversibly intercalated and extracted per MoS 2 is limited, and the chemical and electrochemical processes/mechanisms remain largely unknown, especially for nano-sized materials. Here, in this study, sodiation of MoS 2 nanosheets are studied by in-situ electron diffraction and the phase transformations in sodiation are identified with the aid of DFT calculations to reveal the reaction mechanism. Several thermodynamically stable/metastable structures are identified in the sodiation pathway of MoS 2 nanosheets, previously unnoticed in bulk MoS 2 . The gradual reduction of Mo 4+ upon Na-ion intercalation leads to a transition of the Mo-S polyhedron from a trigonal prism to an octahedron around 0.375 Na per MoS 2 inserted (i.e. Na 0.375 MoS 2 ). When the intercalated Na-content is larger than 1.75 per MoS 2 structural unit (i.e. Na 1.75 MoS 2 ), the MoS 2 layered structure collapses and the intercalation reaction is replaced by an irreversible conversion reaction with the formation of Na 2 S and metal Mo nanoparticles. The calculated sodiation pathways reproduce the experimental sodiation voltages. The current observations provide useful insights in developing sodium-ion batteries with high cycling stability.

25 ENERGY STORAGE↗
DOE OSTI2019

Preparation and redox properties of fluorinated 1,3-diphenylisobenzofurans

Eleven fluorinated 1,3-diphenylisobenzofurans, materials that are promising to perform efficient singlet fission, have been synthesized and their electrochemical reduction and oxidation in non-aqueous dimethylformamide examined. The redox properties are not changed continuously with increasing number of fluorine substituents but there are some qualitative turns in behavior for specific types of substitution revealing a discontinuity requiring deeper investigation. The DFT calculations confirm the trends observed experimentally by correlation of experimental and calculated data. In conclusion, the differences between the geometries of the neutral species and their radical ions were computed and rationalized.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

A family of rare earth molybdenum bronzes: Oxides consisting of periodic arrays of interacting magnetic units

The family of rare earth molybdenum bronzes, reduced ternary molybdates of composition LnMo{sub 16}O{sub 44,} was synthesized and a detailed structural study carried out. Bond valence sum (BVS) calculations clearly show that the molybdenum ions in tetrahedral coordination are hexavalent while the electron count in the primitive unit cell is odd. Yet, measurements show that the phases are semiconductors. The temperature dependence of the magnetic susceptibility of samples containing several different rare earth elements was measured. These measurements verified the presence of a 6.5 K magnetic phase transition not arising from the rare earth constituent, but likely associated with the unique isolated ReO{sub 3}-type Mo{sub 8}O{sub 36} structural subunits in this phase. To better understand the behavior of these materials, electronic structure calculations were performed within density functional theory. Results suggest a magnetic state in which these structural moieties have an internal ferromagnetic arrangement, with small ~1/8 μ{sub B} moments on each Mo. We suggest that the Mo{sub 8}O{sub 36} units behave like pseudoatoms with spin 1/2 derived from a single hole distributed over the eight Mo atoms that are strongly hybridized with the O atoms of the subunit. Interestingly, while the compound is antiferromagnetic, our calculations suggest that a field-stabilized ferromagnetic state, if achievable, will be a narrow band half-metal. - Graphical abstract: LnMo{sub 16}O{sub 44} phases comprise corner sharing tetrahedral and octahedral molybdenum ions. The MoO{sub 6} octahedra form Mo{sub 8}O{sub 36} units that are well separated and act like pseudo-atoms, accommodating 11 electrons each. - Highlights: • Single crystal X-ray diffraction refinements of LnMo{sub 16}O{sub 44} single crystals for Ln=Ce, Pr, Nd, Tb, Dy and Ho. • DFT calculations based on LaMo{sub 16}O{sub 44}. • [Mo{sub 8}O{sub 36}] units behaving as superatoms with a net magnetic moment of 1 µ{sub B}. • Bronze structure containing equal number of molybdenum tetrahedra and octahedral.

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

Quantifying Actinide–Carbon Bond Covalency in a Uranyl–Aryl Complex Utilizing Solution 13 C NMR Spectroscopy

Reaction of [UO 2 Cl 2 (THF) 2 ] 2 with in situ generated LiFmes (FmesH = 1,3,5-(CF 3 ) 3 C 6 H 3 ) in Et 2 O resulted in the formation of the uranyl aryl complexes [Li(THF) 3 ][UO 2 (Fmes) 3 ] ([Li(THF) 3 ][1]) and [Li(Et 2 O) 3 (THF)][UO 2 (Fmes) 3 ] ([Li(Et 2 O) 3 (THF)][1]) in good to moderate yields after crystallization from hexanes and Et 2 O, respectively. Both complexes were characterized by X-ray crystallography and NMR spectroscopy. DFT calculations reveal that the C ispo resonance in [1] – exhibits a deshielding of 51 ppm from spin–orbit coupling effects originating at uranium, which indicates an appreciable covalency in the U–C bonding interaction.

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

Identification of key oxidative intermediates and the function of chromium dopants in PKU-8: catalytic dehydrogenation of sec-alcohols with tert-butylhydroperoxide

Catalytic oxidation using green oxidants has played an important role in modern chemical engineering, however the in-situ generated active groups and the related catalytic mechanism need to be further understood. Combined with several measurements, such as isotopic tracers, molecular probes and cycle voltammetry, chromium ions were observed to undergo a Cr 3+ –Cr 2+ –Cr 3+ redox cycle. Simultaneously, t-BuOO* groups are generated in a large quantity and seem to function as the most critical active species to enhance the dehydrogenation of sec-alcohols when using TBHP as oxidant. DFT calculations give an energetically favorable pathway for TBHP activation, agreeing well with the obtained catalytic results. Here, a reaction scheme was finally proposed to interpret the probable mechanistic process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Cationic Pyridylamido Adsorbate on Brønsted Acidic Sulfated Zirconia: A Molecular Supported Organohafnium Catalyst for Olefin Homo- and Co-Polymerization

Here we report the combined application of high-resolution solid-state 13 C–CPMAS-NMR and FT-IR spectroscopy, elemental analysis, kinetic poisoning/active site counting, variable dielectric constant medium, and DFT computation to characterize the surface chemistry of a pyridylamido hafnium complex (Cat1, L 1 -HfMe 2 , L 1 = 2,6-diisopropyl-N-{(2-isopropylphenyl)[6-(naphthalen-1-yl)pyridin-2-yl]methyl}aniline) adsorbed on Brønsted acidic sulfated zirconia (ZrS). The spectroscopic and DFT results indicate protonolytic formation of organohafnium cations having a largely electrostatic pyridylamido-Hf-CH 3 + ···ZrS - interaction with elongated Hf···OZrS distances of ~ 2.14 Å. High-molecular-weight polyethylenes and ethylene/1-octene copolymers are obtained with this supported catalyst without an activator/cocatalyst. The DFT calculations reveal that the first ethylene insertion into the Hf-methyl bond has a lower barrier than the corresponding insertion into the Hf-aryl bond of this single-site heterogeneous catalyst.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗