DFT-ulg

In the DFT-ulg method of Kim et al.^[1], the correction term takes the form:

E_{\mathrm{disp}} = -\frac{1}{2}  s_{lg}\sum_{i=1}^{N_{at}} \sum_{j=1}^{N_{at}}  \sum_{\mathbf{L}} {}^{\prime}  \frac{C_{6ij}}{r_{ij,L}^{6}+b_{lg}(R_{0}^{ij})^{6}}

where the first two summations are over all $N_{at}$ atoms in the unit cell and the third summation is over all translations of the unit cell ${\mathbf{L}}=(l_1,l_2,l_3)$ where the prime indicates that $i\not=j$ for ${\mathbf{L}}=0$ . $C_{6ij}$ denotes the dispersion coefficient for the atom pair $ij$ , ${r}_{ij,\mathbf{L}}$ is the distance between atom $i$ located in the reference cell $\mathbf{L}=0$ and atom $j$ in the cell $L$ . The parameters in the DFT-ulg method that can be modified are listed below.

VDW_RADIUS=50.0 : cutoff radius (in $\AA$ ) for pair interactions
VDW_S6=0.7012 : global scaling parameter $s_{lg}$ (available in VASP.5.3.5 and later). The default value ( $s_{lg}=0.7012$ ) was determined in conjunction with the PBE GGA functional^[1].
VDW_D=0.6966 : universal correction parameter $b_{lg}$
VDW_C6=[real array] : $C_6$ parameters ( $\mathrm{Jnm}^{6}\mathrm{mol}^{-1}$ ) for each species defined in the POSCAR file
VDW_R0=[real array] : $R_0$ parameters ( $\AA$ ) for each species defined in the POSCAR file
LVDW_EWALD=.FALSE. : the lattice summation in $E_{\mathrm{disp}}$ expression is computed by means of Ewald's summation (.TRUE. ) or via a real space summation over all atomic pairs within cutoff radius VDW_RADIUS (.FALSE.). (available in VASP.5.3.5 and later)