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# IVDW

IVDW = 0 | 1 | 10 | 11 | 12 | 2 | 20 | 21 | 202 | 4
Default: IVDW = 0

Description: This tag controls whether vdW corrections are calculated or not. If they are calculated IVDW controls how they are calculated.

Popular local and semilocal density functionals are unable to describe correctly van der Waals interactions resulting from dynamical correlations between fluctuating charge distributions. A pragmatic method to work around this problem is to add a correction to the conventional Kohn-Sham DFT energy ${\displaystyle E_{{{\mathrm {KS-DFT}}}}}$ :

${\displaystyle E_{{{\mathrm {DFT-disp}}}}=E_{{{\mathrm {KS-DFT}}}}+E_{{{\mathrm {disp}}}}.}$

The correction term ${\displaystyle E_{{{\mathrm {disp}}}}}$ is computed using some of the available approximate methods. The choice of vdW method is controlled via the following tags:

All methods listed above add vdW correction to potential energy, interatomic forces, as well as stress tensor and hence simulations such as atomic and lattice relaxations, molecular dynamics, and vibrational analysis (via finite differences) can be performed. Note, however, that these correction schemes are currently not available for calculations based on density functional perturbation theory.

N.B.: The parameter LVDW used in previous versions of VASP (5.2.11 and later) to activate DFT-D2 method is now obsolete. If LVDW=.TRUE. is defined, IVDW is automatically set to 1 (unless IVDW is specified in INCAR).