Fig. 5: Upsampling performance between functionals.
a Second-order terms for β-quartz / β-cristobalite, in meV/atom. The fields are colored according to the average value and qualitatively indicate the resemblance between the phase spaces of the reference and target functionals. b Correlation between average Si–O bond length and the energy difference between r2SCAN and RPA for β-quartz (blue circles). The black line shows a linear fit. Second-order terms from free-energy perturbation using full energy differences and residuals are written in the lower left corner. The values on the y-axis are offset with respect to the average energy. c Illustration of the Si–O bond length d and Si–O–Si bond angle θ in silica.
