A Simple Theoretical Method to Predict the Hardness of Pure Metal Crystals

Design of superhard bulk materials requires predicting their hardness, challenging current theories for material design. By introducing a concept of condensing force (CF), it is shown via initio calculations for fcc (Ni, Cu, Al, Ir, Rh, Au, Ag, Pd) and hcp Re crystals that materials with larger CF can have greater hardness. Since the calculation of CF is easy, this method might prove a convenient way to evaluate the hardness of newly designed materials.