Please have a closer look at the forum guidelines (link is below). They give some advice for how to be successful in getting help. You need to be aware that people trying to help you are not necessarily experts in your specific area of research and may not be aware of special terms and conventions that may be obvious to you. Good help requires context, but your recent posts have none. I, for example, have absolutely no idea what you mean by “step geometry” (and after me responding to questions about LAMMPS for many years that should tell you something about how much your request needs to be improved for people understand what you are aiming to do) and what it has to do with DPD simulations and thus am unable to make any suggestions except for telling you to post a proper explanation. In these cases, it can often be extremely helpful to provide a small sketch or schematic that outlines what you intend to do.