the critical density and critical temperature, while the converse happens with the modified formulation. The latter also predicts a nearly constant critical density at values of κ , for which the simulation show that this quantity still changes significantly. Nevertheless, the overall agreement with the simulations is quite satisfactory. The paper is organized as follows: in Sec. II the details of our simulations are briefly summarized; in Sec. III, an overview of both the standard and the modified versions of SCOZA is given, and some issues relevant for the application of the theory to short-range interactions are discussed; in Sec. IV our results are presented and discussed; in Sec. V our conclusions are drawn. Canonical ensemble Monte Carlo (NVT-MC) simulations of HCAY fluid interface have been performed using Metropolis algorithm. To prepare the initial configuration we placed N = 1726 particles in a face-centered cubic array in the middle of the simulation cell, which allowed us to obtain two interfaces with a vapor phase surrounding the liquid when the system is equilibrated (see Fig 2 of Ref.[33]). Simulations were performed on a parallelepiped cell with dimensions L$_{x}$ = L$_{y}$ = 10, and L$_{z}$ = 40. Additional MC runs were carried out with L$_{x}$ = L$_{y}$ = 14 and a larger number of particles [37, 38] to check for finite-size effects, and no such effect was found. The cutoff radius was selected to R$_{c}$ = 2. Periodic boundary conditions were applied in all three directions and the neighbor list was applied to speed up calculation. The maximum particle displacement was adjusted to give a 45% acceptance rate. The simulations were performed in cycles; in every cycle it was attempted to move all the particles that are in the neighbor list. The system was equilibrated for 10 6 cycles and the coexistence properties were calculated for 10 7 cycles divided into 100 blocks of 10 5 cycles each one, in order to avoid density fluctuation. The density profiles, ρ ( z ), were calculated every 50 cycles and at the end of each sim- ulation run, every profile was fitted to a hyperbolic tangent function to obtain ρ ∗ V and ρ ∗ L values[33–35]. The critical parameters for the HCAY fluid were calculated by using the rectilinear diameter law [39] and the universal value β coex = 0 . 325 for the critical exponent 4 II. SIMULATION DETAILS