[CP2K-user] [CP2K:15725] PRESSURE TOLERANCE problems when doing cell opt with strain on 2D slab

[Thomas Kühne]

Dear Dragon Don, 

is this an anisotropic system, e.g. a 2D system, with a different hardness along different directions? 

Best, 
Thomas Kühne

> Am 13.07.2021 um 00:49 schrieb Dragon Don <shin... at gmail.com>:
> 
> Dear Thomas Kühne
> 
>   I really appreciate your timely help. It's glad to know that the pressure deviation is not that far off but why, I thought 1300 bar（=13 MPa）is quite huge.
>   Indeed, I have tested another 400 optimization steps, but the pressure deviation changes slightly, just fluctuating around 1300 bar.
>   It's strange that such convergence issue only happens when the strain is loaded along the y axis (My cell is oblique hexagon as shown below). 
>   And the larger the y strain, the further the pressure deviation reaches, even up to 3000 bar for twice the y strain. 
>   In contrast, the pressure deviation can easily converge to 100 bar for x strain loading. The only difference is there are three cell parameters
>   (a,b,γ) that should be settled in y strain loading, while only b and γ need to be calculated for x strain loading. So, Thomas, what can I do to address this issue. 
>   Looking forward to your advice!
>   
>   
> 
> Dragon Don
> 
> 在2021年7月12日星期一 UTC+8 下午8:10:32<tkuehne> 写道：
> Dear Dragon Don?, 
> 
> converging the pressure up to 100 bar is a though call and -1345 bar not that far off. 
> If, however, you are not satisfied by the deviation you simply need to need optimize 
> for longer. But, be aware that the stress tensor sensitively depends on your SCF 
> convergence criterium, so a tight convergence also there is critical! 
> 
> Best, 
> Thomas Kühne
> 
> 
>> Am 11.07.2021 um 14:24 schrieb Dragon Don <sh... at gmail.com <applewebdata://D2A82C74-02D9-4D63-AFCB-921126829B23>>:
>> 
> 
>> Hi everyone！
>> 
>>   Now, I am doing a cell opt with strain by fixing the cell size, while there is a problem that the pressure tolerance can not converge. Could you please give me a hand, looking forward for your help!
>> 
>>   ps. The pics below are the part of the input and output,respectively.
>> 
> 
>>  Don<QQ截图20210711202005.png><QQ截图20210711202109.png>
>> 
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>> <QQ截图20210711202005.png><QQ截图20210711202109.png>
> 
> 
> 
> ==============================
> Thomas D. Kühne
> Dynamics of Condensed Matter
> Chair of Theoretical Chemistry
> University of Paderborn
> Warburger Str. 100
> D-33098 Paderborn
> Germany
> tho... at upb.de <applewebdata://D2A82C74-02D9-4D63-AFCB-921126829B23>
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