I tried to build a model of nanorods by defining a mesomolecular with beads A1B1A1 in DPD,I hope the rod could be stiff enough so I will not be bend during dynamic,I set higher spring constant value and define the angle ABA with high stiffness,but after run dynamic, the beads bond in mesomolecular always be bended.Anyone could give an idea to avoid beads bended in dynamic of DPD,or any other method to build the model for nanorods?