Structure Sensitive Reaction Kinetics of Chiral Molecules on Intrinsically Chiral Surfaces.

Enantiospecific heterogeneous catalysis utilizes chiral surfaces to resolve enantiomers via structure sensitive surface chemistry. The catalyst design challenge is the identification of chiral surface structures that maximize enantiospecificity. Herein, we develop data driven models for the enantiospecificity of tartaric acid reactions on chiral Cu() surfaces.

Pourbaix Machine Learning Framework Identifies Acidic Water Oxidation Catalysts Exhibiting Suppressed Ruthenium Dissolution.

The demand for green hydrogen has raised concerns over the availability of iridium used in oxygen evolution reaction catalysts. We identify catalysts with the aid of a machine learning-aided computational pipeline trained on more than 36,000 mixed metal oxides. The pipeline accurately predicts Pourbaix decomposition energy () from unrelaxed structures with a mean absolute error of 77 meV per atom, enabling us to screen 2070 new metallic oxides with respect to their prospective stability under acidic conditions.

Surface Segregation Studies in Ternary Noble Metal Alloys: Comparing DFT and Machine Learning with Experimental Data.

Surface segregation, whereby the surface composition of an alloy differs systematically from the bulk, has historically been hard to study, because it requires experimental and modeling methods that span alloy composition space. In this work, we study surface segregation in catalytically relevant noble and platinum-group metal alloys with a focus on three ternary systems: AgAuCu, AuCuPd, and CuPdPt. We develop a data set of 2478 fcc slabs with those compositions including all three low-index crystallographic orientations relaxed with Density Functional Theory using the PBEsol functional with D3 dispersion corrections.

Applying Large Graph Neural Networks to Predict Transition Metal Complex Energies Using the tmQM_wB97MV Data Set.

Machine learning (ML) methods have shown promise for discovering novel catalysts but are often restricted to specific chemical domains. Generalizable ML models require large and diverse training data sets, which exist for heterogeneous catalysis but not for homogeneous catalysis. The tmQM data set, which contains properties of 86,665 transition metal complexes calculated at the TPSSh/def2-SVP level of density functional theory (DFT), provided a promising training data set for homogeneous catalyst systems.

: A Semiautonomous Workflow for Systematic Catalyst Surface Reactivity under Reaction Conditions.

This paper introduces , a semiautonomous workflow for modeling the reactivity of catalyst surfaces. The workflow begins with a bulk optimization task that takes an initial bulk structure and returns the optimized bulk geometry and magnetic state, including stability under reaction conditions. The stable bulk structure is the input to a surface chemistry task that enumerates surfaces up to a user-specified maximum Miller index, computes relaxed surface energies for those surfaces, and then prioritizes those for subsequent adsorption energy calculations based on their contribution to the Wulff construction shape.

Machine-learning accelerated geometry optimization in molecular simulation.

Geometry optimization is an important part of both computational materials and surface science because it is the path to finding ground state atomic structures and reaction pathways. These properties are used in the estimation of thermodynamic and kinetic properties of molecular and crystal structures. This process is slow at the quantum level of theory because it involves an iterative calculation of forces using quantum chemical codes such as density functional theory (DFT), which are computationally expensive and which limit the speed of the optimization algorithms.

Semi-grand canonical Monte Carlo simulation of the acrolein induced surface segregation and aggregation of AgPd with machine learning surrogate models.

The single atom alloy of AgPd has been found to be a promising catalyst for the selective hydrogenation of acrolein. It is also known that the formation of Pd islands on the surface will greatly reduce the selectivity of the reaction. As a result, the surface segregation and aggregation of Pd on the AgPd surface under reaction conditions of selective hydrogenation of acrolein are of great interest.

Alchemical Predictions for Computational Catalysis: Potential and Limitations.

Kohn-Sham density functional theory (DFT) is the workhorse method for calculating adsorbate binding energies relevant for catalysis. Unfortunately, this method is too computationally expensive to methodically and broadly search through catalyst candidate space. Here, we assess the promise of computational alchemy, a perturbation theory approach that allows for predictions of binding energies thousands of times faster than DFT.

The atomic simulation environment-a Python library for working with atoms.

The atomic simulation environment (ASE) is a software package written in the Python programming language with the aim of setting up, steering, and analyzing atomistic simulations. In ASE, tasks are fully scripted in Python. The powerful syntax of Python combined with the NumPy array library make it possible to perform very complex simulation tasks.

First-Principles Investigation of the Epitaxial Stabilization of Oxide Polymorphs: TiO on (Sr,Ba)TiO.

Metastable polymorphs, many of which have never been fabricated, have been predicted to exhibit interesting and technologically relevant properties. Epitaxial synthesis is a powerful structure-directing method that can produce metastable polymorphs but is typically done in a trial and error fashion. Unfortunately, the relevant thermodynamic terms governing epitaxial synthesis of new materials are unknown.

Tuning oxide activity through modification of the crystal and electronic structure: from strain to potential polymorphs.

Discovering new materials with tailored chemical properties is vital for advancing key technologies in catalysis and energy conversion. One strategy is the modification of a material's crystal structure, and new methods allow for the synthesis and stabilization of potential materials in a range of crystal polymorph structures. We assess the potential reactivity of four metastable oxide polymorphs of MO2 (M = Ru, Rh, Pt, Ir) transition metal oxides.

Accurate electronic and chemical properties of 3d transition metal oxides using a calculated linear response U and a DFT + U(V) method.

We validate the usage of the calculated, linear response Hubbard U for evaluating accurate electronic and chemical properties of bulk 3d transition metal oxides. We find calculated values of U lead to improved band gaps. For the evaluation of accurate reaction energies, we first identify and eliminate contributions to the reaction energies of bulk systems due only to changes in U and construct a thermodynamic cycle that references the total energies of unique U systems to a common point using a DFT + U(V) method, which we recast from a recently introduced DFT + U(R) method for molecular systems.

Relationships between the surface electronic and chemical properties of doped 4d and 5d late transition metal dioxides.

Density functional theory calculations were performed to elucidate the underlying physics describing the adsorption energies on doped late transition metal dioxide rutiles. Adsorption energies of atomic oxygen on doped rutiles M(D)-M(H)O2, where transition metal M(D) is doped into M(H)O2, were expressed in terms of a contribution from adsorption on the pure oxide of the dopant M(D) and perturbations to this adsorption energy caused by changing its neighboring metal cations and lattice parameters to that of the host oxide M(H)O2, which we call the ligand and strain effects, respectively. Our analysis of atom projected density of states revealed that the t2g-band center had the strongest correlation with adsorption energies.

Electrocatalytic oxygen evolution with an immobilized TAML activator.

Iron complexes of tetra-amido macrocyclic ligands are important members of the suite of oxidation catalysts known as TAML activators. TAML activators are known to be fast homogeneous water oxidation (WO) catalysts, producing oxygen in the presence of chemical oxidants, e.g.

Identifying potential BO2 oxide polymorphs for epitaxial growth candidates.

Transition metal dioxides (BO2) exhibit a number of polymorphic structures with distinct properties, but the isolation of different polymorphs for a given composition is carried out using trial and error experimentation. We present computational studies of the relative stabilities and equations of state for six polymorphs (anatase, brookite, rutile, columbite, pyrite, and fluorite) of five different BO2 dioxides (B = Ti, V, Ru, Ir, and Sn). These properties were computed in a consistent fashion using several exchange correlation functionals within the density functional theory formalism, and the effects of the different functionals are discussed relative to their impact on predictive synthesis.

Effects of strain, d-band filling, and oxidation state on the surface electronic structure and reactivity of 3d perovskite surfaces.

Trends in the dissociative oxygen adsorption energy and oxygen vacancy formation energy on cubic LaBO(3) and SrBO(3) perovskite (001) surfaces (where B = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) and their dependence on strain, d-band filling, and oxidation state were examined using density functional theory in the generalized gradient approximation. The effects of strain were found to be small compared to the effects of d-band filling and oxidations state. Electronic structure descriptors such as the d-band center of the B-atom were identified for trends in the dissociative oxygen adsorption energy and for the oxygen vacancy formation energy.

Effects of strain, d-band filling, and oxidation state on the bulk electronic structure of cubic 3d perovskites.

The properties of the d-band structure of the transition metal atom in cubic LaBO(3) and SrBO(3) perovskites (where B = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) and their dependence on strain, d-band filling, and oxidation state were investigated using density functional theory calculations and atom-projected density of states. The strain dependence of the d-band width is shown to depend systematically on the size of the B atom. We show that the transition metal d-band width and center are linearly correlated with each other in agreement with a rectangular band model.

Configurational correlations in the coverage dependent adsorption energies of oxygen atoms on late transition metal fcc(111) surfaces.

The coverage dependence of oxygen adsorption energies on the fcc(111) surfaces of seven different transition metals (Rh, Ir, Pd, Pt, Cu, Au, and Ag) is demonstrated through density functional theory calculations on 20 configurations ranging from one to five adsorption sites and coverages up to 1 ML. Atom projected densities of states are used to demonstrate that the d-band mediated adsorption mechanism is responsible for the coverage dependence of the adsorption energies. This common bonding mechanism results in a linear correlation that relates the adsorption energies of each adsorbate configuration across different metal surfaces to each other.

CO(2) adsorption on supported molecular amidine systems on activated carbon.

The CO(2) capture capacities for typical flue gas capture and regeneration conditions of two tertiary amidine N-methyltetrahydropyrimidine (MTHP) derivatives supported on activated carbon were determined through temperature-controlled packed-bed reactor experiments. Adsorption-desorption experiments were conducted at initial adsorption temperatures ranging from 29 degrees C to 50 degrees C with temperature-programmed regeneration under an inert purge stream. In addition to the capture capacity of each amine, the efficiencies at which the amidines interact with CO(2) were determined.

Hydrogen dissociation and spillover on individual isolated palladium atoms.

Using a combination of low-temperature scanning tunneling microscopy and density functional theory it is demonstrated how the nature of an inert host metal of an alloy can affect the thermodynamics and kinetics of a reaction pathway in a much more profound way than simply a dilution, electronic, or geometric effect. This study reveals that individual, isolated Pd atoms can promote H2 dissociation and spillover onto a Cu(111) surface, but that the same mechanism is not observed for an identical array of Pd atoms in Au(111).

Step decoration of chiral metal surfaces.

Highly stepped metal surfaces can define intrinsically chiral structures and these chiral surfaces can potentially be used to separate chiral molecules. The decoration of steps on these surfaces with additional metal atoms is one potential avenue for improving the enantiospecificity of these surfaces. For a successful step decoration, the additional metal atoms should ideally remain at the kinked step sites on the surface.

H3PW12O40-functionalized tip for scanning tunneling microscopy.

Recent reports of C(60)-functionalized metal tips [Kelly, K. F., Sarkar, D.