[CP2K-user] [CP2K:22160] Choice of RI basis set fo RPA calculation of argon dimer

[Frederick Stein]

Dear Riccardo,
I did run calculations on Argon and Neon crystals in the past. I found that 
you need additional diffuse basis functions and a BSSE correction for good 
accuracy. For more information on the basis sets, 
check https://www.mdpi.com/1420-3049/25/21/5174 . For the augmentation, you 
can simply use the ones from the Ahlrich basis sets.
Regards,
Frederick

Riccardo Pezzetta schrieb am Freitag, 3. April 2026 um 12:00:05 UTC+2:

> Dear professor Hutter,
> thank you for your answer. Since the only RI basis for argon are the ones 
> in the file BASIS_RI_MOLOPT, would you recommend using the  
> TZV2P-MOLOPT-PBE-GTH-q8 basis set and  RI_AUX RI_85_7_6_5_5_0_0_0_8.0e-08 
> basis set or a correlation consistent basis set like ccGRB-Q-q8 and an 
> auxiliary basis set generated with  auto_basis? With the latter choice I 
> get a worse result, but maybe it is because I have to include the basis set 
> superposition error?
> Kind regards,
>
> Riccardo Pezzetta
>
> Il giorno giovedì 2 aprile 2026 alle 09:41:01 UTC+2 Jürg Hutter ha scritto:
>
>> Hi 
>>
>> the syntax for defining a basis set is 
>>
>> BASIS "TYPE" "NAME" 
>>
>> If "TYPE" is missing it defaults to ORB. If there is more than one BASIS 
>> definition for ORB 
>> the basis sets are combined (e.g. allowing to augment a standard basis 
>> with a difuse set). 
>>
>> Your second input therefore was combining the two basis sets to create a 
>> huge ORB basis 
>> and then used a an automatic procedure to generate a RI basis based on 
>> this huge ORB set. 
>>
>> regards 
>> JH 
>>
>> ________________________________________ 
>> From: cp... at googlegroups.com <cp... at googlegroups.com> on behalf of 
>> Riccardo Pezzetta <richi... at gmail.com> 
>> Sent: Wednesday, April 1, 2026 4:09 PM 
>> To: cp2k 
>> Subject: [CP2K:22149] Choice of RI basis set fo RPA calculation of argon 
>> dimer 
>>
>> Dear CP2K community, 
>> I am trying to calculate the binding energy of the argon dimer using RPA. 
>> I used the basis set TZV2P-MOLOPT-PBE-GTH-q8 from the file BASIS_MOLOPT_UZH 
>> with auxiliary basis set RI_85_7_6_5_5_0_0_0_8.0e-08 from the file 
>> BASIS_RI_MOLOPT: 
>> BASIS_SET TZV2P-MOLOPT-PBE-GTH-q8 
>> BASIS_SET RI_AUX RI_85_7_6_5_5_0_0_0_8.0e-08 
>>
>> With this basis I get -17.9 meV as binding energy. Then I tried to remove 
>> RI_AUX in front of the auxiliary basis set: 
>> BASIS_SET TZV2P-MOLOPT-PBE-GTH-q8 
>> BASIS_SET RI_85_7_6_5_5_0_0_0_8.0e-08 
>>
>> With these parameters i read in the output file: 
>> Orbital Basis Set RI_85_7_6_5_5_0_0_0_8.0e-08TZV2P-MOLOPT- 
>> and 
>> RI Auxiliary Basis Set Ar-RI-AUX-RI_85_7_6_5_5_0_0_0_8.0e-08TZV 
>>
>> It seems that the program mixes the two basis sets, but I don't know how. 
>> The result is -10.6 meV which is closer to the experimental value (which is 
>> -12.3 meV) than the result I obtained writing RI_AUX in front of the 
>> auxiliary basis set. Could anyone explain me what happens with this basis 
>> mixing and tell me if the result based in this parameters is reliable? I 
>> have attached to this message the input and output files. 
>> Thank you in advance. 
>> Kind regards, 
>>
>> Riccardo Pezzetta 
>>
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>>
>

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