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Yu, Haoyu S.

Publications and source records attributed to Yu, Haoyu S..

9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Heats of Adsorption of N 2 , CO, Ar, and CH 4 versus Coverage on the Zr-Based MOF NU-1000: Measurements and DFT Calculations

Equilibrium adsorption isotherms at very low coverage (0 to ~0.1 monolayer) have been measured for four simple gases, N 2 , CO, Ar, and CH 4 , at several temperatures above 98 K on the metal-organic framework (MOF) NU-1000 (which has Zr 6 (μ 3 -OH) 4 (μ 3 -O) 4 (OH) 4 (OH 2 ) 4 nodes linked by pyrenes with -COO - end groups). From these, the differential isosteric heats of adsorption (Q st ) were determined versus coverage. These were compared to density functional calculations of the adsorption enthalpies on different sites, assuming that they are filled in a sequential order from the strongest to weakest binding. This comparison shows excellent quantitative agreement on the trends for the four gases, as well as reasonable agreement in the absolute magnitude of the adsorption energies. Here, this agreement indicates that the sites predicted by the density functional calculations to be populated at different coverages for the different gases are correct, thus further increasing our understanding of adsorption on this prototype MOF.

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

Über Oxidationszahl‐Obergrenzen in der Chemie

Abstract Der Begriff Oxidationszahl ( OS ) ist auf der Basis des Lewis‐Elektronenpaar‐Bildes definiert, wobei Bindungselektronen dem jeweils elektronegativeren Element zugeordnet werden. Der Begriff ist hilfreich zur “Buchhaltung” der Elektronen, zur Vorhersage von chemischen Trends und zur Planung von Synthesewegen. Experimentelle und quantenchemische Befunde legen eine obere Grenze von etwa +8 für die OS in stabilen (neutralen) chemischen Substanzen unter normalen Bedingungen nahe. OS =+9 wurde für das isolierte [IrO 4 ] + ‐Kation in der Gasphase beobachtet. Vorhergesagte OS =+10 für das isolierte [PtO 4 ] 2+ ‐Kation wird hier theoretisch nur für tiefe Temperaturen bestätigt, konnte aber noch nicht experimentell verifiziert werden. Verbindungen mit hoher OS tendieren zur spontanen Reduktion des zentralen Metallatoms unter Oxidation der Liganden, etwa von O −2 unter Bildung von . O −1 und O‐O‐Bindungen, wobei nicht‐Lewis‐konforme Strukturen gebildet werden können.

Hu, Shu‐Xian↗
DOE OSTI2018

On the Upper Limits of Oxidation States in Chemistry

The concept of oxidation state (OS) is based on the concept of Lewis electron pairs, in which the bonding electrons are assigned to the more electronegative element. This approach is useful for keeping track of the electrons, predicting chemical trends, and guiding syntheses. Experimental and quantum-chemical results reveal a limit near +8 for the highest OS in stable neutral chemical substances under ambient conditions. OS=+9 was observed for the isolated [IrO4] + cation in vacuum. The prediction of OS=+10 for isolated [PtO4]2+cations is confirmed computationally for low temperatures only, but hasn't yet been experimentally verified. Lastly, for high OS species, oxidation of the ligands, for example, of O -2 with formation of.O –1 and O–O bonds, and partial reduction of the metal center may be favorable, possibly leading to non-Lewis type structures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Revised M06-L functional for improved accuracy on chemical reaction barrier heights, noncovalent interactions, and solid-state physics

Significance Local exchange−correlation functionals, which depend on the local spin densities, their gradients, and the local spin-specific kinetic energy densities, have been widely used for electronic structure calculations in both chemistry and physics, owing to their computational efficiency in plane wave codes and for large molecules and to their relatively high accuracy for transition metals and other inherently multiconfigurational systems. Minnesota 2006 local functional (M06-L) has proven to be one of the most accurate local functionals currently available, but it has room for improvement with regard to numerical stability and overall accuracy. Here we present a revised M06-L functional, named revM06-L, which gives both smoother potential energy curves and improved overall accuracy, especially for chemical reaction barrier heights, noncovalent interactions, and solid-state physics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Perspective: Kohn-Sham density functional theory descending a staircase

This article presents a perspective on Kohn-Sham density functional theory (KS-DFT) for electronic structure calculations in chemical physics. This theory is in widespread use for applications to both molecules and solids. We pay special attention to several aspects where there are both concerns and progress toward solutions. These include: The treatment of open-shell and inherently multiconfigurational systems (the latter are often called multireference systems and are variously classified as having strong correlation, near-degeneracy correlation, or high static correlation; KS-DFT must treat these systems with broken-symmetry determinants). The treatment of noncovalent interactions. The choice between developing new functionals by parametrization, by theoretical constraints, or by a combination. The ingredients of the exchange-correlation functionals used by KS-DFT, including spin densities, the magnitudes of their gradients, spin-specific kinetic energy densities, nonlocal exchange (Hartree-Fock exchange), nonlocal correlation, and subshell-dependent corrections (DFT+U). The quest for a universal functional, where we summarize some of the success of the latest Minnesota functionals, namely MN15-L and MN15, which were obtained by optimization against diverse databases. Time-dependent density functional theory, which is an extension of DFT to treat time-dependent problems and excited states. Furthermore, the review is a snapshot of a rapidly moving field, and—like Marcel Duchamp—we hope to convey progress in a stimulating way.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Oxidation State 10 Exists

Abstract In a recent paper, Wang et al. found an iridium‐containing compound with a formal oxidation state of 9. This is the highest oxidation state ever found in a stable compound. To learn if this is the highest chemical oxidation state possible, Kohn–Sham density functional theory was used to study various compounds, including PdO 4 2+ , PtO 4 2+ , PtO 3 F 2 2+ , PtO 4 OH + , PtO 5 , and PtO 4 SH + , in which the metal has an oxidation state of 10. It was found that PtO 4 2+ has a metastable state that is kinetically stable with a barrier height for decomposition of 31 kcal mol −1 and a calculated lifetime of 0.9 years. All other compounds studied would readily decompose to lower oxidation states.

Yu, Haoyu S.↗
DOE OSTI2016

Oxidation State 10 Exists

Abstract In a recent paper, Wang et al. found an iridium‐containing compound with a formal oxidation state of 9. This is the highest oxidation state ever found in a stable compound. To learn if this is the highest chemical oxidation state possible, Kohn–Sham density functional theory was used to study various compounds, including PdO 4 2+ , PtO 4 2+ , PtO 3 F 2 2+ , PtO 4 OH + , PtO 5 , and PtO 4 SH + , in which the metal has an oxidation state of 10. It was found that PtO 4 2+ has a metastable state that is kinetically stable with a barrier height for decomposition of 31 kcal mol −1 and a calculated lifetime of 0.9 years. All other compounds studied would readily decompose to lower oxidation states.

Yu, Haoyu S.↗