  Recent first-principle calculations unveiled a distinctive dynamic behavior
in water molecule rotation during the melting process of highly confined water,
indicating a notable time-scale separation in diffusion. In this short paper,
we conducted molecular dynamics (MD) simulations to explore the rotation
dynamics during the mono-layer ice nucleation process to investigate the
possible intermediate states characterized by the differences in rotation of
water molecules. Our study reveals two types of ice clusters with similar ice
geometric structure but possess distinctly different rotational behaviors. In
terms of molecular rotation, one type cluster is ice like (ILC) and can be
regarded as small ice nuclei while the other is supercooled liquid water like
(SCC). We found distinct nucleation pathways, thermodynamic properties, and
phase transition dynamics to associate with these intermediate clusters, which
yielded an unexpectedly complex picture of mono-layer ice nucleation.
