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Dear Collegues,

I started a calculation by setting the tag
LVDW=.TRUE.
and looked into the total energy which differs almost like 16.4 eV from the calculation in which this tag is removed.

I don't think this is reasonable, and i do not know where i am going wrong.

Could you please help.

Here are some additional details.

Total Energy without Dispersion Correction = -1946.740941 eV
Total Energy With Dispersion Correction = -1962.968314 eV

From OUTCAR

Grimme's potential added to compensate for missing vdW interactions
-------------------------------------------------------------------

Parameters for Grimme's potential:
C6(Jnm^6/mol) R0(A)
-----------------------------
O 0.700 1.342
Si 9.230 1.716
C 1.750 1.452
^@^@ 0.000 0.000
H 0.140 1.001

Cutoff radius: 30.000 A
Global scaling factor: 0.750 A
Parameter d: 20.000 A
Number of pair interactions contributing to Grimme's potential: 427374
Estimated vdW energy (eV): -16.36075

I also did calculations by reducing the cutoff radius but that didn't help me too much..

Please help.

Get the Grimme papers, calculate one pair by hand and judge for yourself. Reason will come.

Cheers,

alex