(1) where α ikl control the Gaussian widths, Y lm are the spherical harmonics, and C iklm are the coefficients for the auxiliary basis. These coefficients are the data from which the model is trained and are also the outputs of the model. We used the def2-universal-jfit auxiliary basis for this study. Expressing the density in this form has been shown to be highly efficient in previous machine learning studies. Choice of machine learning algorithm (e3nn)