Time step size |$h=0.001$| and |$\beta =2$|⁠. Here reference solution is obtained by the SAV/CN scheme with a small time step size |$h=0.00002$|⁠. (a) Modified total free energy |$\hat{\mathcal E}$|⁠. (b) Original total free energy |${\mathcal E}$|⁠.