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dDsC dispersion correction
The expression for dispersion energy within the
dDsC dispersion correction [139,138] (DFT-dDsC) is
very similar to that of DFT-D2 method (see eq. 6.87),
the important difference is, however, that the dispersion coefficients
and damping function are charge-density dependent. The dDsC method
is therefore able to take into account variations in vdW contributions
of atoms due to their local chemical environment.
In this method, polarizability, dispersion coeficients, charge
and charge-overlap of an atom in molecule or solid are computed
in the basis of a simplified exchange-hole dipole
moment formalism, pioneered by Becke and Johnson.
The dDsC dispersion energy is expressed as follows
is the number of atoms in the system and is the
Tang and Toennies (TT) damping factor.
The damping function
is defined as follows
and its role is to attenuate the correction at short internuclear
A key component of the dDsC method is the damping factor :
where the fitted parameter controls the short-range behavior
is the damping argument for
the TT-damping factor associated with two separated atoms (
is computed according to the combination rule:
being estimated from effective atomic polarizabilities:
The effective atom-in-molecule polarizabilities
computed from the tabulated free-atomic polarizabilities (available for the
elements of the first six
rows of the periodic table except of lanthanides) in the same way as in the method
of Tkatchenko and Scheffler (see Sec. 6.77.3)
but the Hirshfeld-dominant instead of the conventional Hirshfeld partitioning is used.
The last element of the correction is the damping argument
where and are the nuclear charge and Hirshfeld dominant population of atom , respectively.
is a covalent bond index based on the overlap of conventional
and the fractional term in the parentheses is a distance-dependent ionic bond index.
The DFT-dDsC calculation is invoked by setting IVDW=4.
The default values for damping function parameters are available for
PBE (GGA=PE) and revPBE (GGA=RP).
If other functional is used, the user must
define these parameters via corresponding tags in
INCAR (parameters for common DFT functionals can be found in Ref. )
The following parameters can be optionally defined in INCAR:
||cutoff radius (Å) for pair interactions
Performance of PBE-dDsC in description of the adsorption of
hydrocarbons on Pt(111)
has been examined in Ref.  PCCP 17, 28921 (2015).
- the dDsC method has been implemented into VASP by Stephan N. Steinmann
- this method requires the use of POTCAR files from the
PAW dataset version 52 or later
- the input reference
polarizabilities for non-interacting atoms are available only for elements
of the first six rows of periodic table except of lanthanides
- it is essential that a sufficiently dense FFT grid (controlled via NGFX(Y,Z)) is
used in the DFT-dDsC, especially for accurate gradients - we strongly recommend
to use PREC=Accurate for this type of calculations
(in any case, avoid using PREC=Low).
- the charge-density dependence of gradients is neglected.
This approximation has been thoroughly
investigated and validated.
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