Anionic vacancy filled-up mechanism in (Ti 0.2 V 0.2 Nb 0.2 Ta 0.2 W 0.2 )C x high-entropy carbide

Carbothermic reduction for high-entropy carbide preparation has it's promising potential for industrialization application and the relevant basic theory for formation process required to clarify urgently. This research reports the anionic vacancy filled-up (AVF) mechanism during the formation of (Ti 0.2 V 0.2 Nb 0.2 Ta 0.2 W 0.2 )C x high-entropy carbide powder by predictions of first-principles calculations, thermodynamic phase diagram calculations and verification by experimental preparation and characterization. The mechanism demonstrated that the rock-salt carbide matrix with superfluous anionic vacancy was formed firstly and the residual carbon substance continuously occupied the vacancies to an equilibrium state. The origin of the equilibrium anionic vacancy concentration was revealed from the perspective of the energy variation.