High-Throughput Predictions of the Stabilities of Multi-Type Long-Period Stacking Ordered Structures in High-Performance Mg Alloys.

The effects of 44 types of elements on the stabilities of I1-constitute multi-type long-period stacking-ordered (LPSO) structures in Mg alloys, such as 4H, 6H, 8H, 9R, 12H, 15R, and 16H phases, are systematically investigated by first-principle high-performance calculations. The intrinsic stacking-fault energies (ISFEs) and their increments are calculated along with the formation enthalpies of solute atoms, and interaction energies between solute atoms and LPSO structures. The results suggest that the 15R phase is the easiest to form and stabilize among these LPSO structures, and 44 types of solute atoms have different segregation characteristics in these LPSO structures. A high temperature inhibits structural stabilizations of the LPSO phases, and these alloying elements, such as elements (Sb, Te, and Cs) for 4H; elements (S, Fe, Sb, and Te) for 6H, 8H, 9R, 15R, and 16H; and elements (S, Sb, and Te) for 12H, can effectively promote the stability of LPSO structures at high temperatures. S and Fe atoms are the most likely to promote the stabilities of the 16H structure with regard to other LPSO phases, but the Fe atom tends to inhibit the stabilities of 4H and 12H structures. This work can offer valuable references to further study and develop high-performance Mg alloys with multi-type LPSO structures.

Visible-light photoelectric response in semiconducting quaternary oxysulfide FeOCuS with anti-PbO-type structure.

A novel quaternary oxysulfide, FeOCuS has been successfully synthesized with a tetragonal anti-PbO-type structure and a visible-light bandgap of about 1.37 eV. Driven by only a 0.4 V bias voltage under simulated AM 1.5 G illumination, a high photocurrent density of 3.89 mA cm-2 has been achieved, revealing the potential optoelectronic applications.

First-principles study for stability and binding mechanism of graphene/Ni(111) interface: Role of vdW interaction.

The interaction between graphene and Ni(111) surface has been investigated systematically by density functional theory calculations, in which two different functionals PBE and optB88-vdW are used. PBE calculation indicates no binding between graphene and Ni(111) surface, while optB88-vdW, which is evidenced to consider van der Waals interaction reasonably, predicts the correct binding picture. The accurate potential energy surfaces suggest that top-fcc, bridge-top, and top-hcp are possible stable structures of graphene on Ni(111) surface, which are also found to have very close energies, in agreement with coexistence of different phases found experimentally. Different from PBE, the optB88-vdW functional predicts that top-fcc is the most stable configuration, following by bridge-top and then top-hcp, which is consistent with the surface distribution given by a statistical analysis of high-resolution scanning tunneling microscopy (STM) images. The Dirac points are destroyed in chemisorbed phases of all stable structures. Further analysis indicates that strong hybridization between Ni-3d and C-2p orbitals and asymmetry induced by substrate are responsible for the gap opening at K point. The detailed binding mechanisms have been analysed using differential charge density and the STM images.