“…The unconditional energy stability of the proposed scheme (3.8) follows the idea from the convex-concave decomposition of the energy, an idea popularized in Eyre's work [33]. The method has been applied to the phase field crystal (PFC) equation [41,89]; epitaxial thin film growth models [13,87]; nonlocal gradient model [43]; the Cahn-Hilliard model coupled with fluid flow [14,64], etc. Second-order accurate energy stable schemes have also been reported in recent years, based on either the Crank-Nicolson or BDF2 approach [6,7,22,23,42,44,48,81,90], etc.…”