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

S Ling lingsa... at gmail.com
Thu Sep 21 10:17:42 UTC 2017


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).


On 21 September 2017 at 03:52, Xiaoming Wang <wxia... 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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