  Molecular dynamics simulation is used for studying the contact angle of
nanoscale sessile drops on a planar solid wall in a system interacting via the
truncated and shifted Lennard-Jones potential. The entire range between total
wetting and dewetting is investigated by varying the solid--fluid dispersive
interaction energy. The temperature is varied between the triple point and the
critical temperature. A correlation is obtained for the contact angle in
dependence of the temperature and the dispersive interaction energy. Size
effects are studied by varying the number of fluid particles at otherwise
constant conditions, using up to 150 000 particles. For particle numbers below
10 000, a decrease of the contact angle is found. This is attributed to a
dependence of the solid-liquid surface tension on the droplet size. A
convergence to a constant contact angle is observed for larger system sizes.
The influence of the wall model is studied by varying the density of the wall.
The effective solid-fluid dispersive interaction energy at a contact angle of
90 degrees is found to be independent of temperature and to decrease linearly
with the solid density. A correlation is developed which describes the contact
angle as a function of the dispersive interaction, the temperature and the
solid density. The density profile of the sessile drop and the surrounding
vapor phase is described by a correlation combining a sigmoidal function and an
oscillation term.
