No abstract

The interaction between a solute and vacancy is crucial for the diffusion and precipitation of alloy elements and ultimately affects the creep resistance and safety of refractory molybdenum (Mo) alloys. In this work, the first-principles calculations of the interaction between solutes (5 light impurity atoms and 23 transition metal elements) and vacancies show that Mo is sensitive to all the light impurity elements, which indicates that these solutes are easy to combine with an Mo alloy and have relatively strong interaction. In most cases, the interaction between the 23 transition metal solutes and vacancy is attractive, but the interaction between solutes V, Ti, and the first-nearest vacancy is repulsive, and the interaction between the early elements in the 3d, 4d, and 5d series and the second-nearest vacancy is also repulsive. Then, we discuss the main factors that affect the solute–vacancy interaction, that is, the effects of electron and strain-elimination. Finally, a solute–vacancy interaction database based on the above effects is established, which would contribute to the research on heat- and radiation-resistant Mo alloys.

Chest radiograph shows right-sided volume loss and mediastinal shift from left (L) to right (R). There is no evidence of active pulmonary disease. (B) Volume-rendered chest CT scan shows absence of right upper lobe bronchus (arrow). (C) Volume-rendered CT angiogram from posterior (P) projection shows absence of right upper lobar artery (arrow) and absence of right superior pulmonary vein (arrowhead). A = anterior, ap = anteroposterior.

Two-dimensional (2D) Janus transition metal dichalcogenides (TMDs) are a new class of materials with unique electrical properties. The carrier mobility of Janus TMDs calculated by deformation potential theory (DPT) is unreliable because partial lattice scattering is not taken into account. In this work, we propose a new Born Effective Charge (BEC) method to predict the carrier mobility of Janus TMDs by employing density functional perturbation theory, which includes the important factors neglected in DPT. We have figured out the relationship between carrier mobility and BEC value, that is, the lower the absolute BEC value, the higher the carrier mobility of electrons or holes. The carrier mobilities of commonly used defective and defect-free Janus TMDs were calculated by the new method, and the calculated results are in good agreement with the experimental results. This method can be used for high-throughput calculations to select high-carrier mobility 2D materials, and the data provide a practical paradigm for evaluating carrier mobility in 2D TMDs.