  Inspired by the issue of stability of molecular structures, we investigate
the strict minimality of point sets with respect to configurational energies
featuring two- and three-body contributions. Our main focus is on
characterizing those configurations which cannot be deformed without changing
distances between first neighbors or angles formed by pairs of first neighbors.
Such configurations are called {\it angle-rigid}.
  We tackle this question in the class of finite configurations in
$\mathbb{Z}^2$, seen as planar three-dimensional point sets. A sufficient
condition preventing angle-rigidity is presented. This condition is also proved
to be necessary when restricted to specific subclasses of configurations.
