Generalized Thomas-Fermi approach for systems under pressure

In a previous work one of the authors proposed a simple model for studying systems under pressure based on the Thomas-Fermi (TF) model of single atom. In this work we intend to extend the previous work to more general TF models where electronic exchange and correlation are introduced. To do so, we first study numerically the equation obtained by Lewis (TFDL) which introduces the effects of exchange and correlation into the original TF equation; next the procedure followed in the previous work is extended to the new approach and a specific example is illustrated. Although one could expect that no big differences were produced by the generalized TF model, we show the qualitative as well as quantitative equivalence with detailed numerical results. These results support the robustness of our conclusions with regards to the model proposed in the previous work and give the character of universality (i.e., to pass from one atom to another, the quantities calculated must be simply scaled by a numerical factor) to the properties of compressed systems shown in this work.