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Understanding nanoclusters in the gas phase

We studied the structures of gas-phase gold clusters at finite temperature using van der Waals (vdW) corrected density-functional theory and replica-exchange ab initio molecular dynamics. Including long-range vdW interactions is needed for predicting accurate isomer energetics. Temperature effects are observed to typically stabilize three-dimensional structures over planar structures at finite temperature. Gold cluster structures (Au5-Au13) are assigned based on a comparison of experimental far-infrared multiple photon dissociation spectra performed on Kr-tagged gold clusters with theoretical anharmonic IR spectra and free-energy calculations. Read article here.

Water-catalyzed activation of H2O2 by methyltrioxorhenium

In collaboration with Susannah L. Scott's Group, we conducted a joint computational-experimental study of the reaction of CH3ReO3 (MTO) with H2O2 to understand the origins of large discrepancies in previously reported experimental reaction kinetics and thermodynamics compared with computational results. We also explored MTO-catalyzed olefin epoxidation by H2O2, as it shows strong water acceleration effects, even though no step in the catalytic cycle explicitly consumes water. The main cause of the observed acceleration is the water-dependence of the rates at which the active species are regenerated. Read here and here.

Data mining to discover materials insights

As part of the Novel Materials Discovery Laboratory, a major goal is to develop and exploit data analytics tools to uncover scientific insights from large materials datasets. Dr. Goldsmith's group is using exploratory datamining tools like subgroup discovery to find and describe interesting local patterns in materials data. While at the Fritz Haber Institute and in collaboration with Dr. Mario Boley, two illustrative examples were considered to: (1) discover interpretable models that classify the octet binary materials as either zincblende or rocksalt, and (2) elucidate structure-property relationships of gold clusters in the gas phase. Read here and here.

Single atom formation under reaction conditions

Highly active and selective single atom catalysts can spontaneously form from their nanocluster hosts under reaction conditions. In collaboration with the Wei-Xue Li Group, we conducted an ab initio thermodynamics study to understand the effects of CO and NO reactants on the disintegration of metal-oxide supported Rh, Pd, and Pt nanoparticles into single atom complexes. Read article here.

Modeling isolated catalyst sites on amorphous supports

Isolated metal ions on amorphous supports are widely used in industrial catalytic processes. Modeling isolated sites on amorphous catalyst supports, however, remains a major challenge. To help address this challenge, a systematic ab initio algorithm was created to model isolated active sites on insulating amorphous supports using small cluster models. Read article here. Efforts are being continued to create more realistic models of amorphous supports and to more deeply understand isolated metal ions on amorphous supports, as well as how the amorphous support impacts catalyst performance (e.g., WOx/SiO2 for olefin metathesis).

Synthesis and characterization of Cu-hydride clusters

Copper hydrides have attracted interest for their ability to catalyze the reduction of unsaturated carbonyls, electron deficient alkenes, alkynes, and even CO2. Here, atomically precise copper hydride clusters [Cu14H12(phen)6(PPh3)4]Cl]2, [Cu18H17(PPh3)10]Cl, and [Cu25H22(PPh3)12]Cl were synthesized and characterized in collaboration with the Hayton group. Most remarkably, the [Cu25H22(PPh3)12]Cl is the first copper nanocluster with metallic copper character. Generally, these homogeneous copper clusters represent an opportunity to study the reactivity of Cu nanoclusters, particularly for CO2 reduction. Read here and here.