Phase-field Dislocation Model Of Misfit Dislocations In STO/Si Semicoherent Interface And Dislocation Transmitting Across Al/Pd Coherent Interface

Phase-field Dislocation Model(PFDM) based on Phase-field Micro--elasticity Theory and Peierls-Nabarro Model is established. The Model is used for the research of misfit dislocations in STO/Si semi coherent interface and the behavior of dislocation transmitting across Al/Pd coherent interface.Firstly, on this basis that the elastic continuum theory for elastic anisotropy and homogenous solid, PFDM studied the type of the burgers vector at the low-energy state of the misfit dislocation networks in the STO/Si interface. The influence on the distance between dislocations by the STO layer thickness is simulated and the theoretical formula that describes the distance considering the homogeneous elastic energy in the layer, the dislocation elastic energy and the crystal energy is found. The formula agrees simulation results, which find that with the increase of the STO layer thickness, the distances decrease. 3D model is established based on preliminary fitted γ-surface. The distance in 3D model is smaller than that in 2D model as the overlapping of dislocations makes the energy in the crossing point reduces.Secondly, the relationship between critical stress and the gradient of interface elasticity modulus in Nanoscale Multilayer is calculated and the critical stress is increased when the gradient becomes larger. Nudged Elastic(NEB) Method is introduced in the model and used to compute the activated energy of the whole process including dislocation association and partial dislocations coming across the interface. The results is important to explain the size effect of the yield stress in Nanoscale Multilayer. NEB method is improved that the steps of the NEB iteration is reduced to less than a half of the former ones.Thirdly, the algorithm of PFDM is rewritten to be acceptable for non-uniform data mesh and parallel computing in CPU and CPU+GPU platform. The realization of non-uniform data mesh improves the computational efficiency and decreases the calculation data size. The real speed-up of CPU parallel computing is 80% of the theoretical value and that of CPU+GPU platform is from 10 to 20. These methods help PFDM to simulate 3D large dislocation networks narrowly.