[CP2K:9450] Re: Hybrid functional calculation results show large difference with VASP

[Xiaoming Wang]

Hi Matt,

Actually I also did the calculation for a supercell of 21*21*21 with 320 
atoms. PBE0 without TC are also tested, please see my benchmark tests in 
previous post (attachment in reply to Ling).

Best,
Xiaoming


On Wednesday, September 20, 2017 at 10:27:48 PM UTC-4, Matt W wrote:
>
> That ADMM basis is already pretty large, so whilst it might be the 
> problem, first I'd check the cell size.
>
> Can you build a cell about 15 x 15 x 15 A or larger to allow you to extend 
> the range of the hybrid out to 6 or 7 A?
>
> You are truncating at about 5.25 A, which might not be enough to be fully 
> converged (note VASP won't be doing this as it works in K space). 
>
> Matt 
>
> On Thursday, September 21, 2017 at 8:36:29 AM UTC+8, Xiaoming Wang wrote:
>>
>> Hi Ling,
>>
>> Thanks for your comments. I have attached my benchmark results here. 
>>  Based on my tests, it seems that the ADMM basis set size is not so 
>> important for ionic crystals. One can get reasonable results even with 
>> smallest basis sets. Btw, the cutoff and rel_cutoff used are well converged 
>> values for my target property. So I think there is still room to improve 
>> the ADMM basis for Ag and In (with semicore d states in the valence). To 
>> check whether it is the problem of Ag and In ADMM basis, the simplest way 
>> is to do the PBE0 calculations without ADMM. But the calculation takes me 
>> too long time, as also pointed out by Juerg. I suspect if it is possible to 
>> do HFX without ADMM using MOLOPT basis sets.
>>
>>
>>
>>
>>
>> Best,
>> Xiaoming
>>
>> On Wednesday, September 20, 2017 at 6:20:09 AM UTC-4, S Ling wrote:
>>>
>>> Hi
>>>
>>> I am not sure whether you are using the same ADMM basis sets (see your 
>>> initial input) for these new test calculations. One thing which I can see 
>>> is that you are not using the largest available ADMM basis sets for some of 
>>> the elements, e.g. the largest available ADMM basis sets for Cl, Ag and In 
>>> are pFIT3, FIT12 and FIT13, respectively. Taking In as an example, the 
>>> FIT13 ADMM basis set of In contains more p and d functions than FIT11, 
>>> which may be important for your system. 
>>>
>>> You mentioned a few different functionals, including PBE, PBE0 and 
>>> HSE06, and you have run quite a lot of benchmark tests. It would help if 
>>> you can tabulate all the numbers you have got (including the reference), so 
>>> we can understand your problem better.
>>>
>>> In addition, I can see you're using a CUTOFF of 250 Ry. Please also 
>>> check whether your calculation is converged with respect to this parameter.
>>>
>>> Please also keep in mind that CP2K and VASP use different 
>>> pseudopotentials and basis sets. I wouldn't expect the two codes to give 
>>> the same numbers for your target properties. If you look into literatures, 
>>> you will also find people reporting different numbers for the same property 
>>> using the same method and code.
>>>
>>> SL
>>>  
>>>
>>>
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