[CP2K:9457] Re: Hybrid functional calculation results show large difference with VASP

[Xiaoming Wang]

Hi Vladimir,

Thanks for the reference.

Best,

On Thursday, September 21, 2017 at 11:13:22 AM UTC-4, Vladimir Rybkin wrote:
>
> Dear Xiaoming Wang,
>
> that's why the truncation operator for the exchange integrals is 
> introduced. Please, have a look at reference: 
> http://pubs.acs.org/doi/abs/10.1021/ct900494g
>
> Yours,
>
> Vladimir
>
> четверг, 21 сентября 2017 г., 15:57:45 UTC+2 пользователь Xiaoming Wang 
> написал:
>>
>> I'd like to add that my PBE0 calculation without ADMM basis sets has been 
>> done. I tested 10*10*10 Cs2InAgCl6, which is the system of my original 
>> post. The band gap is 2.52 and 2.50 eV for with and without ADMM. So it 
>> seems not the ADMM basis problem?  
>> I have another question that without ADMM basis sets I have SCF 
>> convergence issue if I don't use the Coulomb truncation method, both for OT 
>> and diagonalization, the SCF didn't tend to converge. Why is that? (The 
>> calculation is fine with TC.)
>>
>> Best,
>>
>> On Thursday, September 21, 2017 at 8:54:49 AM UTC-4, Xiaoming Wang wrote:
>>>
>>> Hi,
>>>
>>> I am sorry for the confusing formula. It is actually Cs2InAgCl6, in 
>>> which Ag is +1. When you are fitting the ADMM basis sets, what's the 
>>> reference system for Ag?  Is it in solid environment? Is it possible for me 
>>> to fit the ADMM basis myself based on my vasp calculations? Well, maybe it 
>>> is too difficult for me, since I am new to cp2k. Btw, do the ADMM basis 
>>> sets depend on the oxidation states of the elements involved? If that's the 
>>> case, there would be problems dealing with different systems with the same 
>>> basis sets. Moreover, the oxidation state is an arbitrary quantity 
>>> depending on the charge partition scheme. The oxidation state may be slight 
>>> different even for the systems which are assumed to be +1 for a particular 
>>> element, for example.
>>>
>>> Best,
>>>
>>> Xiaoming  
>>>
>>> On Thursday, September 21, 2017 at 6:17:45 AM UTC-4, S Ling wrote:
>>>>
>>>> Hi
>>>>
>>>> Can you confirm the chemical formula of your CsInAgCl system? I looked 
>>>> through the ICSD database, and the only related compound which I can find 
>>>> is CsAgInF6, in which Ag is in an uncommon +2 oxidation state (in your 
>>>> benchmark test, you looked at AgCl, in which Ag is in the common +1 
>>>> oxidation state). If this is the case for CsInAgCl6, there is a possibility 
>>>> that your CP2K/PBE0 and VASP/PBE0 calculations may have converged to 
>>>> slightly different SCF solutions. You can check this by comparing the 
>>>> orbital occupation numbers from your VASP/PROCAR and from the CP2K/PDOS 
>>>> analysis. Another possibility is that the ADMM basis sets are indeed not 
>>>> good enough to describe Ag2+ (I have only considered Ag+ when I was fitting 
>>>> the ADMM basis sets of Ag).
>>>>
>>>> SL
>>>>
>>>>  
>>>>
>>>> On 21 September 2017 at 03:52, Xiaoming Wang <wxi... at gmail.com> wrote:
>>>>
>>>>> Hi, Can you see it this time?
>>>>>
>>>>>
>>>>> <https://lh3.googleusercontent.com/-f1GOmo2FRic/WcMpJhTURnI/AAAAAAAAGcU/MqO1xDMjsmQIV1PsgFDq5Aq_IqaPdz-CQCLcBGAs/s1600/benchmark.PNG>
>>>>>
>>>>>
>>>>> On Wednesday, September 20, 2017 at 10:45:10 PM UTC-4, Matt W wrote:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> I only see the check for InCl3, not the main system?
>>>>>>
>>>>>> Matt
>>>>>>
>>>>>> On Thursday, September 21, 2017 at 10:36:15 AM UTC+8, Xiaoming Wang 
>>>>>> wrote:
>>>>>>>
>>>>>>> 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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>>>>
>>>>
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