. The sign of  means the direct sum. The pooling layer is then used for producing an overall feature vector f for the molecule a pooling function, which satisfies permutational invariance concerning atom index and size invariance concerning the same atoms. In this work, an averaged value is used as the pooling function. In addition to the pooling layer, the fully connected hidden layers with activation functions are added to capture the complex mapping between the molecular structure and the potential energy. The structure of the SE3-ETN is shown in Figure in this work.