[CP2K-user] [CP2K:12228] nonscc dftb problem

[simin pahlavi]

Dear Thomas,
Thanks so much for your reply and help.
Regards,
Simin

On Monday, September 16, 2019 at 2:32:03 PM UTC+2, tkuehne wrote:
>
> Dear Simin, 
>
> 1) What about scc dftb? do we need grids there? I mean as far as I 
> undrestoond where ever we use wave-function in cp2k we need grids as it 
> uses amixd of Gaussian s and plane-waves.
>
> also no, it doesn’t make any difference if you are using scc or not. 
>
> 3) But in most of nonscc cases like 100% of cp2k regtest I see that the 
> ewald sum is not used so the electrostatic part is calculated form the 
> direct equation and not ewald sum.
>
> All regtests in the nonscc folder are with PERIODIC NONE, i.e. isolated 
> clusters.
>
> Cheers, 
> Thomas
>
> I appreciate any help in advance,
> Simin Pahlavi
> On Monday, September 16, 2019 at 9:52:45 AM UTC+2, Xin Wu wrote:
>>
>> Hello,
>>
>> On Sunday, September 15, 2019 at 11:49:57 AM UTC+2, simin pahlavi wrote:
>>>
>>> 1) If my input is set up correctly for these type of calculation.
>>>
>>
>> No. There are several errors in the FORCE_EVAL section:
>>
>> 1. MGRID is only relevant to DFT, but not NONSCC-DFTB (please see the DFT 
>> section in the CP2K manual).
>>
>> 2. You have an open QS section, please &END QS.
>>
>> 3. In the POISSON section, you are requesting periodic boundary 
>> conditions. Please enable FORCE_EVAL%DFT%QS%DFTB%DO_EWALD also.
>>
>> 4. There may be some other errors in your input file.
>>  
>>
>>> 2) Normally what the range of cuttof in nonscc dftb should be?
>>>
>>
>> Normally there is no cutoff in DFTB.
>>  
>>
>>> 3) how should I decide on type of mixing , based on convergence speed up 
>>> only?
>>>
>>
>> You're using NONSCC-DFTB. As the name has already implied, there is no 
>> SCF iteration at all.
>>
>> The MIXING approach is only for the SCF procedure. It generates new 
>> density matrix by mixing the electron density in the current iteration with 
>> that from the preceding SCF iteration, so that the variation of electron 
>> density during the SCF procedure becomes smooth and therefore it leads 
>> accelerated convergence. The default values are robust enough for most of 
>> applications. Hence, it's better to use these default settings.
>>  
>>
>>> Thanks in advance,
>>>
>>
>> You're welcome!
>>
>>
>>
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