No min/max C6 in for Van der Waals correction

Hi all, I am running some calculations for a bilayer material (NiI2), and using

vdw_xc 7

to treat the van der Waals interactions. I’m using the PBE functional and PAW datasets.

I noticed in my calculations that abinit prints ******** for the max and min C6:

====> STARTING DFT-D3 computation
Begin the computation of the Coordination Numbers (CN)
required for DFT-D3 energy corrections…
… Done.
max(CN) = 5.69899 (atom 3) ; min(CN) = 4.79827 (atom 6)
Begin the computation of the C6(CN)
required for DFT-D3 energy corrections…
… Done.
max(C6) =******** ; min(C6) =********
Begin the computation of pair-wise term
of DFT-D3 energy contribution…

Van der Waals DFT-D3 semi-empirical dispersion potential
with Becke-Jonhson (BJ) refined by Grimme et al. J.
Comput. Chem. 32, 1456 (2011)

  Scaling factors:       s6 =  1.000,    s8 =  0.787
  Damping parameters:    a1 =  0.429,    a2 =  4.441
  Cut-off radius   =  1.23713E+02 Bohr
  Number of pairs contributing =    98064
  DFT-D3 (no 3-body) energy contribution = -7.04279E-02 Ha

I checked previous calculations of a different material which used vdw_xc 7, and this didn’t occur. But in both cases the DFT-D3 energy contribution has the same order of magnitude, and the calculations here finish without any errors or warnings.

Has anyone come across this before? I’m wondering if I should be worried about this, and if so how I can fix it.


Daniel Bennett