                % Assumption: cutoff ratio applies to particle radius
                        if (int.kinemat.separ >= this.cutoff * p1.radius)
                            % Remove interaction references from particle
                            % (neigh_w is cleaned by searching the id
                            %  to avoid error when it is heterogeneous:
                            %  i.e. different wall types)
                            p1.interacts(p1.interacts==int)   = [];
                          