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

[Vladimir Rybkin]

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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