[CP2K-user] [CP2K:22170] Choice of RI basis set fo RPA calculation of argon dimer

[Riccardo Pezzetta]

Thank you.

Riccardo Pezzetta

Il giorno sabato 4 aprile 2026 alle 11:12:39 UTC+2 Frederick Stein ha 
scritto:

> 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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