Properties of modern materials are significantly affected by crystal-lattice defects, which often do not occur individually but in various combinations. Understanding of such interactions is crucial in contemporary material engineering, however such interactions are often experimentally inaccessible. Here, theoretical approaches, such as ab initio modelling, can help. As a model system for the above mentioned type of interactions, the fcc Ni containing sigma 5(210) tilt grain boundaries (GB), Al and Si impurities and vacancies (Va) in various combinations was chosen. Our modelling was performed by means of the VASP code with projector-augmented plane wave (PAW) potentials.