  There are strong evidences that the melting in two dimensions depends
crucially on the form and range of the interaction potentials between
particles. We study with Monte Carlo simulations the phase diagram and the
melting of a monolayer of point-particles interacting with repulsive Inverse
Power Law Interactions, $V(r)=Q^2(\sigma/r)^n$ where $n$ can take any real
positive value ($n$-OCP monolayer). As $n$ is varied from 0 to $\infty$ (Hard
Disks), including Coulomb ($n=1$) and Dipolar ($n=3$), melting occurs with
different mechanisms and the overall picture permits to understand the
diversity of mechanisms found experimentally or in computer simulations for 2D
melting. The empirical transition curves for $n\leq 3$ and the excellent
qualitative and semi-quantitative agreements with the KTHNY theory found for
the melting of $n$-OCP monolayers with $n\leq 3$ are the main results of the
present work.
