Abstract

Molecular dynamic simulations for systems with D = 2,3 Lennard-Jones-like interactions are studied. In the model, we assume that, at long distances, the two-body attractive potential decays as r(-?). Thermodynamic extensivity (nonextensivity) is observed for ? > D (0 ? ? ? D). Particular attention is paid to the liquid-gas critical point located, in the temperature-pressure plane, at (T(c),P(c)). (T(c),P(c)) are, in the N ? ? limit (N ? number of molecules), finite for ? > D and diverge for ? ? D (as (? - D)-1 for ?/D ? 1 + 0). However, the variables T(c)/(*) ? T(c)/N(*) and P(c)/(*) ? P(c)/N(*) with N(*) ? [N(1-?/D) - 1]/[1 - ?/D] remain finite for all ?. Thus, the extensive and nonextensive regions become unified, as recently conjectured. These results should be useful for discussing gravitation and some special fluids. (C) 1999 Elsevier Science B.V.