2. Material modeling

One of the first steps in the modeling process is to characterize the material system of interest. This is usually a more or less complex mixture of constituents. While the chemical formula and a few physico-chemical properties are generally sufficient to characterize a pure substance, this is not the case for all systems. Some material systems, such as electrolytes, polymers, solids and biological systems, require a more complex representation. In some cases, such as the treatment of hydrocarbon mixtures, it is not possible to include all the constituents in the model, either because they are not all known, or because there are too many of them, or because of a lack of information on their content. We present here a few examples of "complex" mixtures and the modeling approaches adopted.