  The microscopic structure of several amorphous substances often reveals
complex patterns such as medium- or long-range order, spatial heterogeneity,
and even local polycrystallinity. To capture all these features, models usually
incorporate a refined description of the particle interaction which includes an
ad hoc design of the inside of the system constituents. We show that all these
features can emerge from a minimal two-dimensional model where particles
interact isotropically by a double-well potential, and have an excluded volume
and a maximum coordination number. The rich variety of structural patterns
shown by this simple model apply to a wide catalogue of real systems including
water, silicon, and different amorphous materials.
