Enhancing Molecular Dipole Moment Prediction with Multitask Machine Learning

We present a multitask machine-learning strategy for improving the prediction of molecular dipole moments by simultaneously training on quantum dipole magnitudes and inexpensive Mulliken atomic charges. With dipole magnitudes as the primary target and assuming only scalar dipole values are available without vector components, we examine whether incorporating lower-quality labels that do not quantitatively reproduce the target property can still enhance model accuracy. Mulliken charges were chosen intentionally as an auxiliary task since they lack quantitative accuracy yet encode qualitative physical information about charge distribution. Our results show that including Mulliken charges with a small weight in the loss function yields up to a 30% improvement in the dipole prediction accuracy. This multitask approach enables the model to learn a more physically grounded representation of charge distributions, thereby improving both the accuracy and the consistency of dipole magnitude predictions. These findings highlight that even auxiliary data of limited quantitative reliability can provide valuable qualitative physical insights, ultimately strengthening the predictive power of machine-learning models for molecular properties.