Ab initio Interlayer Potentials For Metals and Alloys

Sammanfattning: Many modern materials and material systems are layered. The properties related to layers are connected to interactions between atomic layers. In the present thesis, we introduce the interlayer potential (ILP), a novel model potential which fully describes the interaction between layers. The ILPs are different from the usual interatomic potentials which present interaction between atoms. We use the Chen-Möbius inversion method to extract the ILPs from ab initio total energy calculations. The so obtained ILPs can be employed to investigate several physical parameters connected with the particular set of atomic layers, e.g. surface energy, stacking fault energy, elastic parameters, etc.The interactions between the face centered cubic (fcc) (111) planes are described by two different ILPs. Using two close-packed model structures, namely the ABC stacking along the fcc ?111? direction and AB stacking along the hcp ?0001? direction, we demonstrate how these two ILPs are obtained via the Chen-Möbius method. Density function theory (DFT) is employed to generate the ILPs and also to compute the equilibrium structural properties of elemental metals Al, Ni, Cu, Ag, Au and Pd as well as of Pd-Ag random solid solutions.With the so established ILPs, we adopt the supercell method and the axial interaction model to calculate the stacking fault energy along the fcc ?111? direction, including the intrinsic stacking fault energy, extrinsic stacking fault energy and twin stacking fault energy as well as the interactions between the intrinsic stacking faults. We find that the data derived from ILPs are consistent with those obtained in direct ab initio calculations. Along the fcc ?111? direction, we study the surface energy and surface relaxation using the ILPs. The phonon dispersions are also described.We conclude that the interlayer potentials based on the Chen-M¨obius inversion technique may provide a new way to investigate the properties related to layers in layered materials.