The old Particle-Field Interaction and Fluid-Particle Interaction nodes, which could be added directly to the Charged Particle Tracing and Particle Tracing for Fluid Flow interfaces, respectively, are now obsolete. They will be removed in a future version. Simulations of particle-field and fluid-particle interactions should instead use the dedicated multiphysics nodes.If a model created in version 5.0 or earlier containing the Elastic Collision Force node is opened in version 5.1 or later, this node will be replaced. If the Collision model in the old Elastic Collision Force node was set to Monte Carlo, a Collisions node with the Elastic subnode will be created. If instead the Collision model was set to Friction, the Friction Force subnode will be added.