[CP2K-user] [CP2K:17873] understanding BSSE print out

[Victor Volkov]

Dear members:
good evening/morning.

it is not clear to me how to interpret CP2K print out for BSSE.

If I take a small guest (like benzene) next to a carbon layer using 
GWP/PBE/DZVP
Of course, since interactions are so week, DFTD3 is a must - otherwise a 
benzene may "fly away".

Then, using BSSE  for S1(guest) and S2 (carbon layer)
CP2K prints
S1 + S2ghost: Total energy -455.12112693238430 Hartree
S1ghost + S2: Total energy -455.12112693238430 Hartree
S1           + S2: Total energy -455.12112693238441 Hartree

The differences are none or tiny.

However, the final print is:
CP-corrected Total energy:        0.015729 
1-body contribution:                 -44.96634268204556 
1-body contribution:                -410.13905550190344
2-body contribution:                 455.121127 
BSSE-free interaction energy:      455.121127

*First, it is not clear what is "CP".*

Next, i*f this is the value of the BSSE artifact* (due to the wave-function 
truncation), 
then *its huge* 41.2964895 kJ/mole.
This would be *almost twice larger than the binding energy* of benzene-like 
guests when at carbonaceous surfaces.
This would mean that quality evaluations of binding energies for such 
systems using CP2K would be very difficult. 

Any comments to hear would be nice.

Finally, it is not clear why 2-body contribution and* BSSE-free interaction 
are printed as positive numbers*.

I hope the questions I ask be interesting for users and helpful for the 
on-line manual to update.

After all, I wish to note that it was by a *rare chance I was able to track* 
the old 
notice *on the importance of declaring*
    &KIND X_ghost
     BASIS_SET DZVP-MOLOPT-SR-GTH
     GHOST
    &END KIND 

Even though ... 
*if I skip such definition, the numbers would come "a bit better"*

*:-)*
CP would be about 21 kJ/mole, what is about comparable to the binding 
energy 
of a benzene-like guest to a carbonaceous material. 
 
Thank you for your time and attention.

I wish everybody be well and happy.

Victor

 




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