The
electronic charge density plays a central role in determining
the behavior of matter at the atomic scale, but its computational
evaluation requires demanding electronic-structure calculations. We
introduce an atom-centered, symmetry-adapted framework to machine-learn
the valence charge density based on a small number of reference calculations.
The model is highly transferable, meaning it can be trained on electronic-structure
data of small molecules and used to predict the charge density of
larger compounds with low, linear-scaling cost. Applications are shown
for various hydrocarbon molecules of increasing complexity and flexibility,
and demonstrate the accuracy of the model when predicting the density
on octane and octatetraene after training exclusively on butane and
butadiene. This transferable, data-driven model can be used to interpret
experiments, accelerate electronic structure calculations, and compute
electrostatic interactions in molecules and condensed-phase systems.