  We have carried out extensive equilibrium molecular dynamics (MD) simulations
to study the structure and the interfacial properties in the liquid-vapor (LV)
phase coexistence of partially miscible binary Lennard-Jones (LJ) mixtures. By
analyzing the structural properties as a function of the miscibility parameter,
$ \alpha $, we found that at relatively low temperatures the system separates
forming a liquid A-liquid B interface in coexistence with the vapor phase. At
higher temperatures and, $ 0<\alpha\leq 0.5 $, we found a temperature range,
$T^{*}_{w}(\alpha) \leq T^{*} < T^{*}_{cons}(\alpha)$, where the liquid phases
are wet by the vapor phase. Here, $ T^{*}_{w}(\alpha) $ represents the wetting
transition temperature (WTT) and $T^{*}_{cons}(\alpha)$ is the consolute
temperature of the mixture. However, for $ 0.5< \alpha < 1$, no wetting
phenomenon occurs. For the particular value, $ \alpha=0.25 $, we analyzed
quantitatively the $T^{*}$ versus $\rho^{*}$, and $ P^{*} $ versus $ T^{*} $
phase diagrams and found, $ T^{*}_{c}\simeq 1.25 $, and
$T^{*}_{cons}\simeq1.25$. We also studied quantitatively, as a function of
temperature, the surface tension and the adsorption of molecules at the
liquid-liquid interface. It was found that the adsorption shows a jump from a
finite negative value up to minus infinity, when the vapor wets the liquid
phases, suggesting that the wetting transition (WT) is of first order. The
calculated phase diagram together with the wetting phenomenon strongly suggest
the existence of a tricritical point. These results agree well with some
experiments carried out in fluid binary mixtures.
