Xiaoli Fan

Effect of atomic structure on migration characteristic and solute segregation of ordered domain interfaces formed in Ni75AlxV25-x

Based on the microscopic phase-field model, ordered domain interfaces formed between D022 (Ni3V) phases along [001] direction in Ni75AlxV25-x alloys were simulated, and the effects of atomic structure on the migration characteristic and solute segregation of interfaces were studied. It is found that the migration ability is related to the atomic structure of interfaces, and three kinds of interfaces can migrate except the interface (001)//(002) which has the characteristic of L12 (Ni3Al) structure. V atoms jump to the nearest neighbor site and substitute for Ni, and vice versa. Because of the site selectivity behaviors of jumping atoms, the number of jumping atoms during the migration is the least and the jumping distance of atoms is the shortest among all possible modes, and the atomic structures of interfaces are unchanged before and after the migration. The preferences and degree of segregation or depletion of alloy elements are also related to the atomic structure of interface.

Microscopic phase-field study on directional coarsening mechanism caused by interaction between precipitates in Ni–Al–V alloy

Abstract A microscopic phase-field model was used to investigate a directional coarsening mechanism caused by the anisotropic growth of long period stacking and different effects of phases on precipitation in Ni–Al–V alloy. The results show that DO 22 mainly coarsens along its short axis, which may press the neighboring L1 2 , leading to the interaction among atoms. Diffusion channels of Al are formed in the direction where the mismatch between γ′ and γ reduces; the occupation probabilities are anisotropic in space; and direction coarsening of L1 2 occurs finally. With a rise of ageing temperature, phases appear later and DO 22 is much later at a higher temperature, the average occupation probabilities of Al and V reduce, and Al changes more than V.

First-Principles Study on the Stability and STM Image of Borophene

Very recently, borophene (atomic-thin two-dimensional boron sheet) has been successfully synthesized on the Ag(111) surface by deposition. Two kinds of structures were found. However, the identification of the monolayer boron sheets grown on the metal substrate, as well as the stability of different 2D boron sheets, is controversial. By performing the first-principles calculations, present study investigates the atomic structure, stability, and electronic properties of the most possible boron sheets grown on metal surface, namely, buckled triangular, β12, and χ3 types of crystal lattice. Our result shows that all the three freestanding sheets are thermodynamically unstable and all are metallic. On the other hand, our result indicates the Ag(111) substrate stabilize these sheets. Additionally, our simulated STM images of these monoatomic-thin boron sheets on Ag(111) surface reproduce the experiment observations well and clearly identify the as-grown boron sheets.

Magnetic semiconducting and strain-induced semiconducting–metallic transition in Cu-doped single-layer WSe 2

To pursue the advanced properties of 2D materials, we explore the single-layer WSe2, one of the most studied transitional metal chalcogenide-based magnetic structures. Based on the first-principle calculations, we predict the excellent ferromagnetic coupling between the doped Cu and its nearby Se and W atoms in the single-layer WSe2 (SL-WSe2). Our calculations point out that the Cu-d electrons and the interactions between the dopant and the nearby atoms are the major cause for the induced magnetism. The emerging electronic states around the Fermi level, arising from the doped Cu and its nearby W and Se atoms, not only introduce magnetism into SL-WSe2, but also low its energy gap largely. We also demonstrate a semiconducting–metallic transition in the Cu-doped SL-WSe2 caused by the applied compressive strain and a semiconducting–half metal transition under the applied tensile strain. Moreover, we show the feasibility of doping concentrations and external strain on manipulating the conductivity and magnetism of the Cu-doped SL-WSe2.