Chemical descriptors for describing physico-chemical properties with applications to geosciences.

Chemical descriptors using DFT concepts characterize elements reactivity. Such descriptors, namely hardness and electrophilicity, are components of the derivative of the chemical potential. Their values form a new coordinates system, on which a third parameter can be mapped. The simplest mapping is the chemical potential itself, but other mapping may involve totally different chemical or physical parameters. Examples use rock analyses generated within the continental or oceanic crust of the Earth. They are usually described in an 11D system of major oxides. The new system of coordinates reduces the description to a more easily tractable 2D diagram. It also represents a base for plotting other chemical information, such as the normative component composition or a combination of them. Physically, other properties, such as the polymerization state or viscosity values, can be used to produce a 3D topography. Other topographic surfaces similar to the chemical potential of elements can be mapped, allowing quantification of partition coefficient values when elements fractionate in both liquid or viscous states. The reduction of an 11D diagram to a 2D one is suggested in other scientific descriptions of complex combinations. Graphical abstract [ω-η] diagrams showing the chemical potential and the different continental and oceanic rock typesthen ading some chemical (Aluminium Saturation Index) parameter.