  The supercritical state is currently viewed as uniform on the
pressure-temperature phase diagram. Supercritical fluids have the dynamic
motions of a gas but are able to dissolve materials like a liquid. They have
started to be deployed in many important industrial applications stimulating
fundamental theoretical work and development of experimental techniques. Here,
we have studied local structure of supercritical matter by calculating static
structure factor, mean force potential, self-diffusion, first coordination
shell number and pair distribution function within very wide temperature
ranges. Our results show a monotonic disappearance of medium-range order
correlations at elevated temperatures providing direct evidence for structural
crossover in the reciprocal and real spaces. Importantly, the discovered
structural crossover in the reciprocal space is fundamentally inter-related to
structural crossover in the real space, granting new unexpected interlinks
between operating system properties in the supercritical state. Finally, we
discuss an evolution analysis of the local structure and important implications
for an experimental detection of structural monotonic transitions in the
supercritical matter.

Statistical Mechanics;Disordered Systems and Neural Networks;Materials Science;Soft Condensed Matter