In order to obtain the most stable configuration for the aluminum segregation in the GB, we use the Basin Hopping algorithm which is based on the canonical Monte Carlo technique, where the algorithm alters the coordinates of the current structure to a new structure according to a predefined constraint and then geometrically optimizes it. The optimized new structure can be accepted or rejected based on the Metropolis criterion. The results are interpreted using aluminum insertion energy as defined in Equation cluster on an alumina substrate under varying hydrogen pressures. 43