The Vickers hardness (H V ) of the new phosphides has been predicted using two contemporary models: the thermodynamic (T) model , which is based on thermodynamic properties and crystal structure, and shows perfect agreement with available experimental data , and the empirical Mazhnik-Oganov (MO) model , which is based on elastic properties. The results are summarized in Table . Both qtz and zinc-blende BP are (super)hard phases, while the hardness of all AlP polymorphs is three times lower.