Search

An exact, computationally efficient density functional theory (DFT) ansatz is derived using the asymptotic limits of large and small interatomic separations. A generalization of the Anderson-Weeks-Adams-Gilbert chemical pseudopotential theory of localized atomic states, asymptotic density functional theory (ADFT) recasts the Kohn-Sham equations in a simple, self-consistent Huckel form that features nonempirical Hamiltonian matrix elements and explicit exchange-correlation (XC), electrostatic, and orthogonalization effects. The theory provides fundamental justification for several characteristics of successful tight binding models, most notably the atomic additivity of electron density and the potential and the pairwise additivity of interatomic XC, electrostatic, and Pauli repulsion effects. The Sanderson electronegativity equalization principle and the charge equilibration mechanism resembling the Rappe-Goddard scheme naturally follow. ADFT offers a bridge between molecular orbital, valence bond, and DFT theories and holds promise to accelerate accurate quantum chemical calculations., 24 pages, 103 equations

Carbon-supported, Pt and PtCo nanocrystals (NCs) with controlled size and composition were synthesized and examined for hydrodeoxygenation (HDO) of 5-hydroxymethylfurfural (HMF). Experiments in a continuous flow reactor with 1-propanol solvent, at 120 to 160 °C and 33 bar H2, demonstrated that reaction is sequential on both Pt and PtCo alloys, with 2,5-dimethylfuran (DMF) formed as an intermediate product. However, the reaction of DMF is greatly suppressed on the alloys, such that a Pt3Co2 catalyst achieved DMF yields as high as 98%. XRD and XAS data indicate that the Pt3Co2 catalyst consists of a Pt-rich core and a Co oxide surface monolayer whose structure differs substantially from that of bulk Co oxide. Density functional theory (DFT) calculations reveal that the oxide monolayer interacts weakly with the furan ring to prevent side reactions, including overhydrogenation and ring opening, while providing sites for effective HDO to the desired product, DMF. We demonstrate that control over metal nanoparticle size and composition, along with operating conditions, is crucial to achieving good performance and stability. Implications of this mechanism for other reactions and catalysts are discussed.