Perturbation Theories for the Thermodynamic Properties of Fluids and Solids

28 Perturbation Theories for Fluids and Solids

(Verlet 1968, Vliegenthart et al. 1999); at low k the structure factor decays to values

much lower than 1 and for high enough densities S(0) →0, reflecting the fact that the

fluid becomes nearly incompressible. The main peak is placed at k

0

=2π/r

0

, where

r

0

is slightly lower than σ (Verlet 1968), which means that the position of the first

peak is determined by the effective size of the particles. At moderate densities, the

shape of the structure factor of the LJ fluid departs from that of the HS fluid, as

shown in Figure 2.5. For the latter, in particular, as k is lowered from the value k

0

corresponding to the first peak, the structure factor continuously decreases toward the

k = 0 value. In contrast,