Four public datasets (PhysProp, Martel, Star & NonStar, 23 and Huuskonen ) were used for training and testing the HDNN model with q -ACSFs con f , as shown in Figure and Figure . Two homemade datasets (n-carboxylic acids and Solv-54 ) were adopted as an external test (Table ). PhysProp database is perhaps the biggest public collection of the experimental log P data. It contains about 41039 molecular structures as SMILES strings in total, 13553 of which were determined experimentally and the rests were estimated. In Martel, 707 commercial molecules were measured experimentally with high performance liquid chromatography (HPLC) method. Star & Non-Star database is composed of 266 molecules, 223 of which were picked from BioByte StarList for the development of various log P estimation methods. The other 43 molecules were collected outside of BioByte StarList. Huuskonen database contains a diverse set of 1870 organic molecules.