In this paper, the Dol3 package with the density functional theory (DFT) was used to calculate the energy parameters and the electronic properties of the simulation models. Moreover, the Perdew-Burke-Ernzerhof (PBE) functional was selected to treat the exchange correla-tion energy [21]. The calculation accuracy of energy, force and displacement were set to 1 × 10−5 Ha, 2 × 10−3 Ha/Å, and 5 × 10−3
Ha/Å, respectively. As the default setting, the Double numerical plus polarization (DNP) was selected for further calculation. The semi-core pseudopotential (DSPP) was applied for core electrons calculation due to its relativistic effects [22–24]. The k point of the Brillouin zone integration was 5 × 5 × 1, and the self-consistent (SCF) field tolerance was set to 1 × 10−6 Ha in this study. In addition, in order to accelerate the convergence of SCF charge density, the direct inversion of iterative subspace (DIIS) size was set to 6 [25–27]. The influence of spin-polarization can be ignored in the study. A 4 × 4 × 1 MoS2 monolayer supercell was built. The vacuum distance was set to 20 Å in order to avoid the interactions between adjacent layers. The lattice parameter of MoS2 monolayer obtained by optimization calculation is 3.18 Å, which matches well with the theoretical and the experimental values (3.18 Å; 3.20 Å) obtained from the previous studies [28–30]. In addition, one Au or Ag atom bonds with three S atoms on the upper surface of MoS2 monolayer to form the doped MoS2 monolayer.
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https://www.sciencedirect.com/science/article/pii/S1386947719301262(1) I am not able to understand what is the density functional value selected here.
(2) Where the force and displacement value mentioned above, do they stand for force tolerance and maximum step size?
(3) What does SCF field tolerance represents?
