今天来学习一下 vasp的scan计算
先来看一下官网定义 ** METAGGA=SCAN The SCAN (Strongly constrained and appropriately normed) [7] functional is a semilocal density functional that fulfills all known constraints that the exact density functional must fulfill. There are indications that this functional is superior to most gradient corrected functionals [8]. This functional is only available as of VASP version ≥ 5.4.3. ** METAGGA=RSCAN The rSCAN (regularized SCAN) functional [9], introduces regularizations that improve the numerical sensitivity and convergence behavior. These regularizations break several of the exact constraints that the parent SCAN functional was designed to satisfy. However, testing has indicated that the accuracy of rSCAN can be inferior to SCAN in some cases [10]. This functional is available as of VASP version ≥ 6.2.0. ** METAGGA=R2SCAN The r{\displaystyle ^{2}}^{2}SCAN (regularized-restored SCAN) functional [11] modifies the regularizations introduced in rSCAN to enforce adherence to the exact constraints obeyed by SCAN. It fulfills all known constraints. However, it only recovers the slowly varying density-gradient expansion for exchange to second order, while SCAN recovers the expansion to 4th order. Testing indicates that r{\displaystyle ^{2}}^{2}SCAN at least matches the accuracy of the parent SCAN functional but with significantly improved numerical efficiency and accuracy under low-cost computational settings. This functional is available as of VASP version ≥ 6.2.0, or in version 5.4.4 by patch 4. **
