The indices i and j ∈ S denote the center atom of the convolution and the neighboring atoms of i within a cut-off distance, respectively. The V lu,pu bcmu denotes the feature vectors of the input u that comprise a direct sum of irreducible representation of the O(3) symmetry group. The "rotation order" l u = 0, 1, 2,... is a non-negative integer and parity is one of p u ∈ (-1, 1) which together label the irreducible representations of O(3). The indices b, c, m u , correspond to the atoms, the channels (elements of the feature vector), and the representation index which takes values m ∈ [-l, l], respectively. Furthermore, C indicates the Clebsch-Gordan coefficients. It should be noted that the placement of indices into sub-and superscript does not carry specific meaning. Moreover, only output tensors with l o ≤ l max are taken into account.