### vanderWaals interactions (IVDW) and consistency

Posted:

**Mon Feb 01, 2021 10:26 am**Dear Vasp Community,

I have a question regarding the nature of the IVDW corrections and how to be consistent when calculating properties.

I am modeling graphene sheets (slabs) with deposited alkali-ions on them and I am using IVDW = 11 to account for VdW.

To find the adsorption energy (or voltage) with respect to the metal (using as reference the bulk and not an isolated atom in a vacuum).

We need to have the Eg (energy of empty graphene sheet), Em (energy of 1 atom in the bulk metal), and Egm (energy of metal and graphene).

In order to be consistent, do I have to apply the same correction to all three calculations?

For example, the Eg and Egm need the correction but the Em does not. (based on the size and geometry)

Further, if I apply the correction to the metal I get a big shift in energy affecting the results quite significantly (while physically it shouldn't).

Example: 1 Na-metal atom without IDVW:

Checking a lot of literature on adsorption and reproducing simple calculations of 1 atom depositions on graphene (trying to replicate their numbers) revealed that they most probably

Do you have any advice in terms of consistency and what is the correct approach?

Thank you very much for your valuable help

Alexandros

I have a question regarding the nature of the IVDW corrections and how to be consistent when calculating properties.

I am modeling graphene sheets (slabs) with deposited alkali-ions on them and I am using IVDW = 11 to account for VdW.

To find the adsorption energy (or voltage) with respect to the metal (using as reference the bulk and not an isolated atom in a vacuum).

We need to have the Eg (energy of empty graphene sheet), Em (energy of 1 atom in the bulk metal), and Egm (energy of metal and graphene).

In order to be consistent, do I have to apply the same correction to all three calculations?

For example, the Eg and Egm need the correction but the Em does not. (based on the size and geometry)

Further, if I apply the correction to the metal I get a big shift in energy affecting the results quite significantly (while physically it shouldn't).

Example: 1 Na-metal atom without IDVW:

**-1.307eV**and with IDVW=11:**-1.469eV**Checking a lot of literature on adsorption and reproducing simple calculations of 1 atom depositions on graphene (trying to replicate their numbers) revealed that they most probably

**do not apply**the corrections to the metal but apply it only to the Eg and Egm.Do you have any advice in terms of consistency and what is the correct approach?

Thank you very much for your valuable help

Alexandros