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Zr-based amorphous alloys have attracted extensive attention because of the large glassy formation ability, wide supercooled liquid region, high elasticity and unique mechanical strength induced by their icosahedral local structures. To dig out the microstructures of Zr-Cu clusters, the stable and metastable geometry of Zr n Cu (n=2~12) clusters are screened out via CALYPSO method using machine learning potentials, and then the electronic structures are investigated using the density functional theory. The results show that the Zr n Cu (n≥3) clusters possess the three-dimensional geometries, Zr n Cu (n≥9) possess cage-like geometries and the Zr12Cu cluster has icosahedral geometry. The binding energy per atom gradually enlarged with increased size of clusters, and Zr n Cu (n=5, 7, 9, 12) have relative stronger stability than their neighbors. The magnetic moment of most Zr n Cu clusters is just 1μ B , and the main components of HOMOs in Zr12Cu cluster comes from Zr-d state. There are hardly any localized two-center bonds, and there are about 20 σ-type delocalized three-center bonds.

In this paper, the growth pattern, magnetic and electronic structure of VLin (n = 2–13) clusters are studied using density functional theory in generalised gradient approximation. The growth pattern showed that the VLin (n = 2–13) clusters favoured the three-dimensional configuration and appeared cage-like structures with increasing size. The average binding energy, second-order energy difference and dissociation energy are discussed, and the VLi12 cluster is magnetic superatom. The spin magnetic moment of VLi12 cluster is 1 μB and the molecular orbital arrangement is 1S21P61Dα51Dβ4. The chemical bonding patterns of the VLi12 cluster was obtained by using molecular orbital analysis and the adaptive natural density partitioning method.

The stable geometries, electronic structures, and magnetic behaviors of the ScLi n (n = 2–13) clusters are investigated by using particle swarm optimization (PSO) and density functional theory (DFT). The results show that these clusters have three-dimensional (3D) structures except ScLi2, and ScLi12, and ScLi13 that possess the cage-like structures. In analyses of the average binding energy, second-order difference of energy, and fragmentation energy, ScLi12 cluster is identified as magnetic superatom. The magnetic moment for each of these clusters owns an oscillating curve of different cluster sizes, and their magnetic moments are further investigated using molecular orbitals and jellium model. Of ScLi n (n = 2–13) clusters, ScLi12 has the largest spin magnetic moment (3 μ B), and molecular orbitals of ScLi12 can be described as 1 S 2 1 P 6 1 D α 5 D β 2 . Additionally, Mulliken population and AdNDP bonding analysis are discussed and the results reveal that the Sc atom and Li n atoms make equal contribution to the total magnetic moment, and atomic charges transfer between Sc atoms and Li atoms.

Quenching of highly vibrationally excited CsH(X1Σ+, v = 15–23) by collisions with CO2 was investigated. A significant fraction of the initial population of highly vibrationally excited CsH(v = 22) was relaxed to a low vibrational level (Δv = −5). The near-resonant 5–1 vibration-to-vibration (V–V) energy was efficiently exchanged. The rate constants for the rotational levels of CO2(0000) [J = 36–60] and CO2(0001) [J = 5–31] from the collisions with excited CsH were determined. The experiments revealed that the collisions resulting in CO2(0000) were accompanied by substantial excitation in rotation and translation. The vibrationally excited CO2(0001) state exhibited rotational and translational energy distributions near those of the initial state. The total quenching rates relative to the probed state of excited CsH were determined for both CO2 states. The corresponding data indicated that the gains in the rotational and translational energies in CO2 were sensitive to the collisional depletion of excited CsH.

The N-methyl bis-imidazolium salts 3 were converted to the silver carbenes 7, then reacted to give palladium(II) complexes 4 with trans-chelating, bidentate bis-imidazolylidine ligands. The similar salts 8, that do not have N-methyl substituents, gave the tetradentate complexes 9 in direct reactions with palladium chloride. The potential of these complexes for asymmetric catalysis is discussed.

The carbene complex 1 can mediate hydrogenations of dienes with up to 20∶1.0 diastereoselectivity and 99% ee; the scope and limitations of these reactions were investigated.

This work explores the potential of iridium complexes of the N-heterocyclic carbene oxazoline ligands 1 in asymmetric hydrogenations of arylalkenes. The accessible carbene precursors, imidazolium salts 2, and robust iridium complexes 5 facilitated a discovery/optimization approach that featured preparation of a small library of iridium complexes, parallel hydrogenation reactions, and automated analysis. Three of the complexes (5ab, 5ad, and 5dp) and a similar rhodium complex (6ap) were studied by single-crystal X-ray diffraction techniques. This revealed molecular features of 6ap, and presumably the corresponding iridium complex 5ap, that the others do not have. In enantioselective hydrogenations of arylalkenes complex 5ap was the best for many, but not all, substrates. The enantioselectivities and conversions observed were sensitive to minor changes to the catalyst and substrate structure. Ligands with aliphatic N-heterocyclic carbene substituents gave complexes that are inactive, and do not lose the 1,5-cyclooctadiene ligands under the hydrogenation conditions. Experiments to investigate this unexpected observation imply that it is of a steric, rather than an electronic, origin. Temperature and pressure effects on the conversions and enantioselectivities of these reactions had minimal effects for some alkenes, but profound effects for others. In one case, the enantioselectivities obtained at high-pressure/low-temperature conditions were opposite to those obtained under high-temperature/low-pressure conditions (-64% enantiomeric excess versus +89% enantiomeric excess); a transformation from one prevalent mechanism to another is inferred from this. The studies of pressure dependence revealed that many reactions proceeded with high conversions, and optimal enantioselectivities in approximately 2 h when only 1 bar of hydrogen was used. Deuterium-labeling experiments provide evidence for other types of competing mechanisms that lead to D-incorporation at positions that do not correspond to direct addition to the double bond.

Density functional theory (PBE and B3LYP) was used to study asymmetric hydrogenations of alkenes catalyzed by an iridium imidazolylidine oxazoline complex. The calculation predicts that the alkene preferentially coordinates to the site trans to the carbene. The coordinated alkene then reacts first with the H2 ligand, then with the hydride to form alkane. Finally, the alkane is released by equilibrating with extrinsic H2 and alkene. Enantioface selectivities for hydrogenations of trisubstituted alkenes seem to be driven primarily by steric interactions with the adamantyl part of the ligand; only the smallest substituents can adopt a site close to it. Application of this theoretical model leads to correct predictions regarding the experimentally observed sense and magnitude of the enantioselectivities.

Chemical cleaning, vacuum firing, glow discharge cleaning, and in situ bakeout have become standard practices for removing surface contaminants in the ultra high vacuum systems of particle accelerator and storage rings. In this work, an alternative method, reactive gas cleaning with nitric oxide (NO), has been studied. It was applied to several accelerator vacuum chambers made of stainless steel with surfaces ranging from clean to heavily contaminated by hydrocarbons. The effectiveness of the NO treatment has been compared with those of other treatments and found to be superior to vacuum firing alone, and is comparable with that of glow discharge cleaning.

Chemical cleaning, vacuum firing, glow discharge cleaning, and in situ bakeout have become standard practice for lowering the outgassing rate and removing surface contaminants in the ultrahigh vacuum systems of particle accelerators and storage rings. This paper presents the work done with the thermal outgassing of several long stainless‐steel (304LN and 316L) beam chambers with areas of more than 1×104 cm2 . They were measured between 20 and 500 °C after vacuum firing, glow discharge cleaning, or reactive gas (nitric oxide) cleaning. Outgassing rates of low 10−13 and low 10−14 Torr 1/s cm2 were achieved for H2 and CO, respectively, with vacuum firing alone. The outgassing of H2 in this temperature range is consistent with that due to bulk diffusion with an enthalpy of 9±1 kcal/mole. The photon stimulated desorption of the chamber surface after the above treatments were also studied by exposure to an intense photon beam at the National Synchrotron Light Source. The effectiveness and merits of reactive gas cleaning in removing the surface contaminants in large vacuum systems are compared to those of vacuum firing and glow discharge cleaning.