# [CP2K:10528] Huge difference in adsorption energies between CP2K and VASP with PBE

hut... at chem.uzh.ch hut... at chem.uzh.ch
Sat Jul 14 16:28:13 UTC 2018

```Hi

assuming you did all calculations correctly, you should have the following 7 energies ready

System      Geometry from      Basis

1  A+B          A+B            A+B
2  A            A              A
3  B            B              B
4  A            A+B            A
5  A            A+B            A+B
6  B            A+B            B
7  B            A+B            A+B

The uncorrected adsorption energy is     :  E1 = (1) - (2+3)

Counterpoise correction energy is        :  E2 = ((4)-(5)) +((6)-(7))

BSSE corrected adsorption energy is      :  Ea = E1 + E2

E1 is too negative because of BSSE.
Counterpoise correction is positive because larger basis stabilises systems.
Typically the counterpoise correction is 0-50% of the non-corrected energy
(depending on the system and the basis)

regards

Juerg

--------------------------------------------------------------
Juerg Hutter                         Phone : ++41 44 635 4491
Institut für Chemie C                FAX   : ++41 44 635 6838
Universität Zürich                   E-mail: hut... at chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
---------------------------------------------------------------

From: "Sharma SRK Chaitanya Yamijala"
Date: 07/14/2018 01:59AM
Subject: Re: [CP2K:10528] Huge difference in adsorption energies between CP2K and VASP with PBE

I just want to add that, the energy of the CO obtained through the one body contributions (listed in the output of a BSSE calculation) and the energy of the optimized CO (in the same cell size but without the slab) is found to be exactly the same. To me, this suggests the current basis should be accurate enough as one should expect a larger effect of the BSSE on CO rather than on slab (as slab contributes to the large portion of basis functions of the total system). Kindly, let me know if my logic is wrong.

--------------------------------------------------------------------
SRK Chaitanya Sharma, Yamijala.
http://www.bmwong-group.com/group-members/

On Fri, Jul 13, 2018 at 1:16 PM, Sharma SRK Chaitanya Yamijala <sharma... at gmail.com> wrote:
And I believe the increase in the adsorption energy could be because of the non-ground-state geometry of the "slab" during the BSSE calculation. The slab's absolute energy when considered in the monomer basis (for the ground state geometry) is -9804.47553 au and it is -9804.468056 au for the geometry in the dimer configuration (i.e. for the slab geometry in the "slab + CO" optimized geometry).

--------------------------------------------------------------------
SRK Chaitanya Sharma, Yamijala.
http://www.bmwong-group.com/group-members/

On Fri, Jul 13, 2018 at 12:29 PM, Sharma SRK Chaitanya Yamijala <sharma... at gmail.com> wrote:
Dear Prof. Hutter,

I have performed the BSSE corrections and the results are given below. Clearly, the BSSE corrected interaction energy is huge (~ 1 eV). If I consider this CP-corrected energy as the adsorption energy (I have calculated adsorption energy as Eads = EAB - EA -EB), then it will be too off from the VASP (-0.466 eV) or FHIAIMs (-0.595 eV) results. As mentioned, without BSSE the calculated adsorption energy is -0.863 eV. All the energies given are with Grimme's-D3 dispersion. Kindly, let me know if you have any comments about this.

To check the accuracy of my basis set, I have started a run with TZVP basis (instead of DZVP) for adsorption energy calculation and I will update here.

On a different note, the number of basis functions used for the calculation in FHIAIMS (6172) and CP2K (5660) is roughly the same.
-------------------------------------------------------------------------------
-                                                                             -
-                                 BSSE RESULTS                                -
-                                                                             -
-                 CP-corrected Total energy:        0.039208                  -
-                                                                             -
-                       1-body contribution:    -9804.468056                  -
-                       1-body contribution:      -21.667247                  -
-                                                                             -
-                       2-body contribution:     9826.174511                  -
-                 BSSE-free interaction energy:     9826.174511               -
-------------------------------------------------------------------------------

Thanks,
Sharma.

--------------------------------------------------------------------
SRK Chaitanya Sharma, Yamijala.
http://www.bmwong-group.com/group-members/

On Fri, Jul 13, 2018 at 12:31 AM,  <hut... at chem.uzh.ch> wrote:
Hi

you are using a DZVP basis, this is rather small. Check the number
of basis functions. Do the same for the FHIaims calculation
and compare.
The cutoff of VASP cannot be compared to a local basis set.

regards

Juerg Hutter
--------------------------------------------------------------
Juerg Hutter                         Phone : ++41 44 635 4491
Institut für Chemie C                FAX   : ++41 44 635 6838
Universität Zürich                   E-mail: hut... at chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
---------------------------------------------------------------

From: "Sharma SRK Chaitanya Yamijala"
Date: 07/12/2018 07:55PM
Subject: Re: [CP2K:10514] Huge difference in adsorption energies between CP2K and VASP with PBE

Dear Prof. Hutter,

Thanks. I will try the BSSE correction with CP2K. Regarding k-point sampling, in both the softwares, I have used Gamma point only. Could you please elobarate your point on "size of basis sets" here? I don't know how should I compare VASP basis (plane waves) with CP2K (both PW and Gaussians)? I have converged the CUTOFFs in both the cases such that the energy differences are < 1 meV.

Also, yesterday, I have performed similar calculations with FHIAims and I have obtained the adsorption energy (withOUT dispersion and BSSE corrections) as 0.412 eV which is again closer to the VASP result and to the result in the reference.

Thanks,
Sincerely,
Sharma.

On Thursday, July 12, 2018 at 12:11:59 AM UTC-7, jgh wrote:Hi

my first guess: you didn't calculate the BSSE correction.

other possible contributions: size of basis sets
k-point sampling

regards

Juerg Hutter
--------------------------------------------------------------
Juerg Hutter                         Phone : ++41 44 635 4491
Institut für Chemie C                FAX   : ++41 44 635 6838
Universität Zürich                   E-mail: hut... at chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
---------------------------------------------------------------

From: "Sharma SRK Chaitanya Yamijala"
Date: 07/12/2018 01:48AM
Subject: [CP2K:10507] Huge difference in adsorption energies between CP2K and VASP with PBE

Dear CP2K members,

I am calculating the adsorption energies of CO on ZnO (4x4-slab with 4 layers of ZnO(10-10) surface). The adsorption energy obtained from VASP is ~ 0.3 eV (without dispersion) and it is ~ 0.45 eV (with dispSECTION_PARAMETERS TRUEersion). However, when calculating the same system with CP2K (geometry is re-optimized), I am obtaining the energies 0.688 eV and 0.863 eV for without and with dispersion correction, respectively.

The literature value is close to the VASP result. Here is the reference (kindly, see Table 2, C-down, 2x1 cell, Full).

B Meyer and D Marx 2003 J. Phys.: Condens. Matter 15 L89
http://iopscience.iop.org/article/10.1088/0953-8984/15/2/112/pdf

Could anyone give an advice on why there is such a discrepancy in the adsorption energies irrespective of using the same functional?

I am attaching the geometry and the input file for your reference.

Thanks,
Sharma.

--------------------------------------------------------------------
SRK Chaitanya Sharma, Yamijala.
http://www.bmwong-group.com/group-members/

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[attachment "1CO_on_opt_4x4_slab.xyz" removed by Jürg Hutter/at/UZH]
[attachment "zno_bulk.inp" removed by Jürg Hutter/at/UZH]

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