We create a virtual library of 1.5 million small organic molecules using our library generator code ChemLG in constrained combinatorial mode. This library is constructed based on the sequential combinatorial linking of the 15 molecular building blocks shown in Fig. for four generations, while enforcing certain constraints, i.e., a molecular weight within the range of 150 to 400 Dalton and limiting the number of ring-moieties to four. The hydrogen atoms in each building block are used as linker handles. Our proof-of-principle library is designed to feature different connections between simple moieties, most of which are commonly used in organic materials (except B5, B8, and B9). We use the eToxPred software to compute the synthetic accessibility score (SAscore) of all 15 building blocks and obtain similarly favorable values between 2.4 and 2.9 on the 1-10 scale (with 1 being the most synthetically accessible). We provide the details of the accessibility analysis in the Supplementary Material. Our generation approach limits the size of the library while yielding both a diverse set of compounds as well as candidates with more subtle differences for the model to distinguish. The complete library is provided in the Supplementary Material. To facilitate the density evaluation for a large number of compounds via the MD modeling protocol introduced in Sec. II A, we employ our automated virtual highthroughput screening framework ChemHTPS . ChemHTPS creates inputs for the MD simulations, executes the modeling protocol, monitors the calculations, parses and assesses the results, and extracts and processes the information of interest. Of the 1.5 million compounds in our screening library, we randomly select a subset of 100,000 for study at the MD level.