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

[Matt W]

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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