We consider a point defect in a homogeneous crystalline solid. We can show that the formation free energy as well as the transition rate between two stable configurations converge as the number of atoms tends to infinity and characterise the limit. Both cases can be reduced to a careful renormalisation analysis of the vibrational entropy difference, which is achieved by identifying an underlying spatial decomposition of said entropy. (This is joined work with Hong Duong and Christoph Ortner)