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The HO···XCCNgF and HN···XCCNgF (X = Cl and Br; Ng = Ar, Kr, and Xe) complexes have been studied with quantum chemical calculations at the MP2/aug-cc-pVTZ level. The results show that the inserted noble gas atom has an enhancing effect on the strength of halogen bond, and this enhancement is weakened with the increase of noble gas atomic number. The methyl and Li substituents in the electron donor strengthen the halogen bond. The interaction energy increases from −3.75 kcal/mol in HN-BrCCF complex to −9.66 kcal/mol in HLiN-BrCCArF complex. These complexes have been analyzed with atoms in molecules, natural bond orbital, molecular electrostatic potentials, and energy decomposition calculations. [ABSTRACT FROM AUTHOR]

Nickel is widely used as a bleaching element in white gold alloys, but it is a potential allergen. In this paper, a popular 18 KW gold alloy, often called 'safe nickel,' was chosen as the experimental material; its nickel release rates under six different processing conditions were evaluated according to the EN1811 standard. The results reveal that both the surface processing method and heat treatment technology significantly affect the nickel release rate. A coarse surface releases more nickel ions than a smooth surface. The sample normalized at 700 °C in the single region has a lower nickel release rate than the one treated at 550 °C in the two-phase phase region, while high temperature normalizing at 800 °C will accelerate it. All the measured nickel release rates of the experimental material under various processing conditions exceed the permitted threshold value in the Nickel Directive, which indicates that there exists the potential risk of nickel-induced allergy when it is used to make jewelries, especially for piercing types. Graphical abstract: The surface topography of W4 sample after soaking in artificial sweat for one week, there are a large number of corrosion pits on the surface, which shows that the material under sand blasting is subjected to serious corrosion, and the nickel release rate will be accelerated.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]