## Steinhardt order parameter The order parameter shows the symmetry of the local structure. It contains/is made up of spherical harmonic faction for a structure closer to N fold geometry, the $Q_N$ gets larger, or say, closer to 1. (like $Q_4$ for 4-fold geometry, and $Q_6$ for 6-fold geometry) >[!Note] >The expression can be found at this [page](https://pyscal.org/en/documentation_changes/methods/steinhardtparameters/traditionalsteinhardtparameters.html#:~:text=Steinhardt's%20bond%20orientational%20order%20parameters%20%5B1%5D%20are%20a%20set%20of,explore%20the%20local%20atomic%20environment.). $q_l (i) = \Big( \frac{4\pi}{2l+1} \sum_{m=-l}^l | q_{lm}(i) |^2 \Big )^{\frac{1}{2}}$ >where >$q_{lm} (i) = \frac{1}{N(i)} \sum_{j=1}^{N(i)} Y_{lm}(\pmb{r}_{ij})$