Simulation of inclined dendrites under natural convection by KKS phase field model based on CUDA

In this work,Al-4.5wt.%Cu was selected as the research object,and a phase field-lattice Boltzmann method(PF-LBM)model based on compute unified device architecture(CUDA)was established to solve the problem of low serial computing efficiency of a traditional CPU and achieve significant acceleration.This model was used to explore the evolution of dendrite growth under natural convection.Through the study of the tip velocities,it is found that the growth of the dendrite arms at the bottom is inhibited while the growth of the dendrite arms at the top is promoted by natural convection.In addition,research on the inclined dendrite under natural convection was conducted.It is observed that there is a deviation between the actual growth direction and the preferred angle of the inclined dendrite.With the increase of the preferred angle of the seed,the difference between the actual growth direction and the initial preferred angle of the inclined dendrite shows a trend of increasing at first and then decreasing.In the simulation area,the relative deflection directions of the primary dendrite arms in the top right corner and the bottom left corner of the same dendrite are almost counterclockwise,while the relative deflection directions of the other two primary dendrite arms are clockwise.

Modulation of CO adsorption on 4,12,2-graphyne by Fe atom doping and applied electric field

Adsorption characteristics of CO adsorbed on pristine 4,12,2-graphyne(4,12,2-G)and Fe-doped 4,12,2-graphyne(Fe-4,12,2-G)are studied by first-principles calculations.It is shown that CO is only physically adsorbed on pristine 4,12,2-G.Fe atoms can be doped into 4,12,2-G stably and lead to band gap opening.After doping,the interaction between Fe-4,12,2-G and CO is significantly enhanced and chemisorption occurs.The maximum adsorption energy reaches-1.606 e V.Meanwhile,the charge transfer between them increases from 0.009e to 0.196e.Moreover,the electric field can effectively regulate the adsorption ability of the Fe-4,12,2-G system,which is expected to achieve the capture and release of CO.Our study is helpful to promote applications of two-dimensional carbon materials in gas sensing and to provide new ideas for reversible CO sensor research.

Rectification and phase locking of graphite

Rectification phenomena and the phase locking in a two-dimensional overdamped Frenkel-Kontorova model with a graphite periodic substrate were studied. The presence of dc and ac forces in the longitudinal direction causes the appearance of dynamicalmode locking and the steps in the response function of the system. On the other hand, the presence of an ac force in the transverse direction causes the appearance of rectification,even though there is no net dc force in the transverse direction. It is found that whereas the longitudinal velocity increases in a series of steps, rectification in the transverse direction can occur only between two neighbor steps. The amplitude and phase of the external ac driving force affect the depinning force,rectification of the system and particles trajectories.