Practically all the case studies in this book involve systems whose interactions are expressed in terms of continuous potentials. As a consequence, the dynamical equations can be solved numerically with constant-timestep integration methods. If one is prepared to dispense with this continuity another route is available that offers several advantages, although it has its weak points as well. The alternative method is based on step potentials; hard spheres are the simplest example, but the method can be extended to include potentials that have the shape of square wells or barriers, and even flexible ‘molecules’ can be built. Quantitative comparisons with specific real substances are obviously not the goal here, ...