Efficiently searching extreme mechanical properties via boundless objective-free exploration and minimal first-principles calculations

Despite the machine learning(ML)methods have been largely used recently,the predicted materials properties usually cannot exceed the range of original training data.We deployed a boundless objective-free exploration approach to combine traditional ML and density functional theory(DFT)in searching extreme material properties.This combination not only improves the efficiency for screening large-scale materials with minimal DFT inquiry,but also yields properties beyond original training range.We use Stein novelty to recommend outliers and then verify using DFT.Validated data are then added into the training dataset for next round iteration.We test the loop of training-recommendation-validation in mechanical property space.By screening 85,707 crystal structures,we identify 21 ultrahigh hardness structures and 11 negative Poisson’s ratio structures.The algorithm is very promising for future materials discovery that can push materials properties to the limit with minimal DFT calculations on only~1%of the structures in the screening pool.