  The location of the Frenkel line (FL) of a Lennard-Jones fluid which
demarcates two distinct physical states, liquidlike and gaslike within the
supercritical regime, has been established through molecular dynamics (MD)
simulations of the velocity auto-correlation (VACF) and Radial distribution
Function (RDF). We, in this article, explore the changes in the structural
features of supercritical LJ-fluid under partial confinement using atomistic
walls. The study is carried out across the FL through a series of MD
simulations considering a set of thermodynamics states in the supercritical
regime of Argon well above the critical point. Confinement is partial, with
atomistic walls located normal to z and extending to "infinity" along the x and
y directions. In the "liquidlike" regime of the supercritical phase, particles
are distributed in distinct layers along the z with layer spacing less than one
atomic diameter and the lateral RDF showing amorphous-like structure for
specific spacings (packing frustration). Increasing the rigidity of the
atomistic walls is found to lead to stronger layering and increased structural
order. For confinement with reflective walls, layers are found to form with one
atomic diameter spacing and the lateral RDF showing close-packed structure for
the smaller confinements. Translational order parameter and excess entropy
assessment confirm the ordering taking place for atomistic wall and reflective
wall confinements. In the "gaslike" regime of the supercritical phase, particle
distribution along the spacing and the lateral RDF exhibit features not
significantly different from that due to the normal gas regime. The
heterogeneity across FL, found to be present both in bulk and confined systems,
might cause the breakdown of the universal scaling between structure and
dynamics of fluids necessitating the determination of a unique relationship
between them.
