Bimetallic Pb n Cu n (n = 2–14) clusters were investigated by density functional theory

3-Mercaptopropionic/3-Mercaptoisobutyric Acids Used as Novel Selective Depressants for Improved Flotation of Chalcopyrite from Galena

The selective separation of chalcopyrite from galena (lead sulfide) through the flotation method is still a challenging task in the field of mineral engineering. Mercaptoacetic acid, though a common depressant of many gangue (commercially worthless) minerals, has shown to be less selective in the flotation separation of chalcopyrite and galena. This resent study therefore systematically investigated the selectivity of different mercapto acids (especially three types: 3-mercaptopropionic acid, 3-mercaptoisobutyric acid and mercaptoacetic acid) on the separation of chalcopyrite and galena by making the use of flotation experiments and first principle calculations. The calculation results demonstrated that the sulfhydryl and carboxyl groups existing on the molecular structure of three mercapto acids are the reactive and chelating centers to metal ions on sulfide mineral surfaces. Mercapto acids have higher binding energies to Cu2+ by 300–400 kJ/mol compared to Pb2+, indicating a higher affinity towards chalcopyrite. The order of reactivity and chelating ability noted was as follows: 3-mercaptopropionic acid > 3-mercaptoisobutyric acid > mercaptoacetic acid. Flotation results further showed that the selectivity of 3-mercaptopropionic acid or 3-mercaptoisobutyric acid was better than mercaptoacetic acid. The good agreement between the first principle calculations and the flotation results demonstrated that the former reagent could be served as a most selective depressant in the improved flotation separation of chalcopyrite and galena.

Exploration of the Structural, Electronic and Tunable Magnetic Properties of Cu₄M (M = Sc-Ni) Clusters

The structural, electronic and magnetic properties of Cu₄M (M = Sc-Ni) clusters have been studied by using density functional theory, together with an unbiased CALYPSO structure searching method. Geometry optimizations indicate that M atoms in the ground state Cu₄M clusters favor the most highly coordinated position. The geometry of Cu₄M clusters is similar to that of the Cu₅ cluster. The infrared spectra, Raman spectra and photoelectron spectra are predicted and can be used to identify the ground state in the future. The relative stability and chemical activity are investigated by means of the averaged binding energy, dissociation energy and energy level gap. It is found that the dopant atoms except for Cr and Mn can enhance the stability of the host cluster. The chemical activity of all Cu₄M clusters is lower than that of Cu₅ cluster whose energy level gap is in agreement with available experimental finding. The magnetism calculations show that the total magnetic moment of Cu₄M cluster mainly come from M atom and vary from 1 to 5 μ_B by substituting a Cu atom in Cu₅ cluster with different transition-metal atoms.

Theoretical insights into the structural, relative stable, electronic, and gas sensing properties of PbnAun (n = 2–12) clusters: a DFT study

The structural, relative stable and electronic properties of Pb_nAu_n (n = 2–12) clusters are the first time to be reported, and Pb_nAu_n (n = 4, 6, 8) clusters may serve as gas sensors.