  We study computationally the local structure of aggregated systems of patchy
particles. By calculating the probability distribution functions of various
rotational invariants we can identify the precursors of orientation order in
amorphous phase. Surprisingly, the strongest signature of local order is
observed for 4-patch particles with tetrahedral symmetry, not for 6-patch
particles with the cubic one. This trend is exactly opposite to their known
ability to crystallize. We relate this anomaly to the observation that a
generic aggregate of patchy systems has coordination number close to 4. Our
results also suggest a significant correlation between rotational order in the
studied liquids with the corresponding crystalline phases, making this approach
potentially useful for a broader range of patchy systems.
