Hetero and Homo Metal Exchange of Au25(SR)18 - and Ag25(SR)18 - Clusters with Metal-Thiolate Complexes: Ab Initio Molecular Dynamics Simulation Studies.

The hetero and homo metal exchange of Au25(SR)18 - and Ag25(SR)18 - nanoclusters with metal-thiolate (M-SR) complexes (AuI(SR), AgI(SR), CuI(SR), and CuII(SR)2) are studied using ab initio molecular dynamics (AIMD) simulations. The AIMD simulation results unveil that the M-SR complexes directly displace Au(SR) or Ag(SR) units on the gold or silver core surface through an "anchoring effect". The whole process of metal-exchange reactions can be divided into three steps, including the adsorption of M-SR complexes on clusters, the formation of new staple motif, and the displacement of Au(SR) or Ag(SR) units by M-SR complexes. The key role of sulfur atoms in metal exchange reactions in M-SR complexes is revealed, which facilitates formation of new staple motifs and doping of M-SR complexes into gold and silver cores. This work provides a theoretical basis for further exploring the metal exchange reaction between noble metal nanoclusters and metal-thiolate complexes, as well as the isotope exchange reactions.

Molecular Dynamics Simulation Study on the Growth of Structure II Nitrogen Hydrate.

Crystal growth of N2 hydrate in a three-phase system consisting of N2 hydrate, liquid water, and gaseous N2 was performed by molecular dynamics simulation at 260 K. Pressure influence on hydrate growth was evaluated. The kinetic properties including the growth rates and cage occupancies of the newly formed hydrate and the diffusion coefficient and concentration of N2 molecules in liquid phase were measured. The results showed that the growth of N2 hydrate could be divided into two stages where N2 molecules in gas phase had to dissolve in liquid phase and then form hydrate cages at the liquid-hydrate interface. The diffusion coefficient and concentration of N2 in liquid phase increased linearly with increasing pressure. As the pressure rose from 50 to 100 MPa, the hydrate growth rate kept increasing from 0.11 to 0.62 cages·ns-1·Å-2 and then dropped down to around 0.40 cages·ns-1·Å-2 once the pressure surpassed 100 MPa. During the hydrate formation, the initial sII N2 hydrate phase set in the system served as a template for the subsequent growth of N2 hydrate so that no new crystal structure was found. Analysis on the cage occupancies revealed that the amount of cages occupied by two N2 molecules increased evidently when the pressure was above 100 MPa, which slowed down the growth rate of hydrate cages. Additionally, a small fraction of defective cages including two N2 molecules trapped in 51265 cages and three N2 molecules trapped 51268 cages was observed during the hydrate growth.

Visualization data on concentrating apple juice with a trinitarian crystallization suspension freeze concentrator.

This article contains visualization data on concentrating apple juice with a trinitarian suspension crystallization freeze concentrator, which integrates scraped-surface heat exchanger, suspension crystallizer and wash-column into one piece of equipment. The visualization data on ice accumulation, ice bed development and consolidation in the crystallizer/wash-column of the freeze concentrator are presented in a set of photographs in chronological order and videos attached as appendix materials. These data refer to the related research article entitled "Concentration of Apple Juice with an Intelligent Freeze Concentrator" Ding et al., 2019.