[CP2K-user] Slow calculating speed of HSE06

[Matt W]

Yeah. This is correct. You need the interaction to basically decay by half 
the cell length or weirdness might occur.

On Friday, April 9, 2021 at 6:32:53 PM UTC+1 n... at berkeley.edu wrote:

> Another thing I suspect is tripping up this small system is the HFX 
> implementation in CP2K. The way CP2K calculates HFX means that periodicity 
> isn't handled nicely (maybe Matt can comment on why this is?) and so the HF 
> interaction potential needs to decay before it reaches periodic images, 
> this is why most people who are doing CP2K will use a truncated PBE0 with 
> the truncation radius of 1/2 the minimum cell dimension. For HSE06, the the 
> effective interaction distance is 1 / screening = 1 / .2 = 5 Angstroms. So 
> for a primitive cell like you have, you're actually probably unphysically 
> including HF effects across the periodic boundary, which could be what's 
> making the calculation take so long. Just further reason to use cp2k for 
> larger cells.
>
> On Friday, April 9, 2021 at 6:09:07 AM UTC-7 Matt W wrote:
>
>> I hadn't seen the earlier messages in another thread. At a quick glance 
>> your input looks fine. I'd decrease EPS_DEFAULT to 10^-14 or something to 
>> be sure things were set up accurately. Make sure you restart from a GGA 
>> converged solution.
>>
>> It will, of course, get more expensive for bigger cells but in the limit 
>> of really big cells only linearly with sytem size. 
>>
>> CELL_OPT can be quite expensive with hybrids. You could just do a volume 
>> sweep with static calcs as you have a cubic cell.
>>
>> Matt
>> On Friday, April 9, 2021 at 1:31:02 PM UTC+1 ma... at gmail.com wrote:
>>
>>> Dear Matt,
>>>
>>> Yes, I know GAMMA point for such a small system doesn't make sense. I 
>>> did this calculation just for exercise because I thought small system will 
>>> save time. I thought a small system already took such a long time, the 
>>> larger system would take much longer. But based on your description, it 
>>> seems what I though is totally wrong. I would run some large supercell 
>>> systems later. Thanks!
>>> By the way, regarding the attached input file that I used, could you 
>>> please have a look when you are free and provide some suggestions that may 
>>> improve the performance (e.g., speed and stability) based on your expertise?
>>>
>>> Thanks & Regards,
>>> Hongyang
>>>
>>> 在2021年4月9日星期五 UTC+10 下午10:12:47<Matt W> 写道：
>>>
>>>> You can't run an 8 atom system without k-points, it doesn't make sense 
>>>> and you can't run hybrid functionals with k-points at the moment.
>>>>
>>>> Absolute minimum is a 64 atom system (still nowhere near converged). 
>>>> For the HSE screened exchange, I'd suggest you wil need box dimensions of 
>>>> _at least_ 1 nm on each side otherwise strange things will happen. 
>>>>
>>>> If ADMM is working well the extra cost of going to bigger systems will 
>>>> not be too big. Plane wave code will be more efficient for the smallest 
>>>> cells, but CP2K should win out for bigger defect cells.
>>>>
>>>> Matt
>>>>
>>>> On Friday, April 9, 2021 at 9:47:52 AM UTC+1 ma... at gmail.com wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> I'm a beginner of using cp2k7.1. My aim is to use HSE06 to calculate 
>>>>> the Si (8 atoms) system. However the calculating speed is extremly slow. I 
>>>>> used OT and ADMM approaches and GAMMA point with 48 cores, but this 
>>>>> CELL_OPT calculation took around 30 mins to finish. As a comparison, I used 
>>>>> VASP to run the same geometry with HSE06 and with only 1 core, the 
>>>>> calculation finished in 50 seconds... So clearly, I must did something 
>>>>> wrong in the input file resulting in a significant limitation in the 
>>>>> calculating speed but I couldn't figure out which part is wrong. Could 
>>>>> somebody please provide some help? Thanks.
>>>>>
>>>>> Regards,
>>>>> Hongyang
>>>>>
>>>>
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