A first approach is the use of computational techniques to allow the use of larger simulation boxes, or longer simulation times -while retaining the use of PBC. This enables the computational determination of dynamic properties of the flexible frameworks on large length scales, directly probing the nature of the transitions at a scale of multiple unit cells. It is important, for example, to distinguish between structural transitions that occur uniformly through a cooperative motion of all cells, and those that proceed "domain by domain", creating an interface with two phases coexisting (temporarily) inside the crystal itself. This approach had previously been applied to simplified representations of MOF models ("toy models"), providing qualitative understanding of the nature of transitions, . However, its application to realistic systems with an atomic level of description is a new development in the field.