[CP2K-user] [CP2K:21496] Re: frequencies

[Sihem AZIZI]

thanks a lot


On Tuesday, May 20, 2025 at 10:44:22 AM UTC+1 Frederick Stein wrote:

> Dear Sihem,
> Apparently, your input file arrived after I started writing my message. I 
> suggest you to optimize the cell seperately as stress tensor calculations 
> are very costly and not too accurate as with a modulating cell sizes, 
> integration grids will also change. If you know that your cell has a fixed 
> shape with a single parameter (cubic, hexagonal cell with 2D peridocity, 
> ...), you should rather run several calculations while varying the cell 
> parameter and fitting a Burch-Murnaghan equation of states. If a single 
> SCF+force calculation still takes too much, you should switch to another 
> computer if possible or wait for a very long time. Generally, you should 
> optimize all accuracy and performance relevant parameters with this 
> SCF+force calculation.
> HTH,
> Frederick
>
> Frederick Stein schrieb am Dienstag, 20. Mai 2025 um 11:33:15 UTC+2:
>
>> Dear Sihem,
>> Without any further information (input and output file), it is hard to 
>> give any recommendations. Optimize the force calculation by making the 
>> calculation as accurate as necessary and as 
>> cheap as possible (CUTOFF, EPS_DEFAULT, EPS_SCF, play around with mixing 
>> schemes, ...).
>> Regards,
>> Frederick
>>
>> Sihem AZIZI schrieb am Dienstag, 20. Mai 2025 um 11:30:12 UTC+2:
>>
>>> Dear frederick,
>>> Thanks a lot for your response.
>>> I have another question for you. On another machine I ran an 
>>> optimization calculation for a Ru slab (3 layers) with an H2 molecule. And 
>>> the calculation has been running for a month. What should I do to make it 
>>> converge faster?
>>> Thank you again for your help.
>>> Sihem
>>>
>>> On Monday, May 19, 2025 at 9:05:04 PM UTC+1 Frederick Stein wrote:
>>>
>>>> Dear Sihem,
>>>> How much time do you need for a force calculation on the same machine 
>>>> with 8 processes? Your total runtime will be 6*<number of atoms> in your 
>>>> system as the elements of the Hessian will be determined from symmetric 
>>>> finite difference quotients of the analytical gradients. Please be aware 
>>>> that a vibrational analysis requires a very accurate setup especially with 
>>>> your required displacement. Your EPS_SCF is definitely too low for that, 
>>>> your CUTOFF and the EPS_DEFAULT in the QS section could be also improved. 
>>>> The general recommendation is a value 1.0E-7 to 1.0E-8 for EPS_SCF. You 
>>>> need analytical gradients with an accuracy of several digits as too noisy 
>>>> gradients will render the frequencies meaningless. The expected differences 
>>>> in gradients should be at least one or two orders of magnitude higher than 
>>>> the accuracy of the gradients.
>>>> Best,
>>>> Frederick
>>>>
>>>> Sihem AZIZI schrieb am Montag, 19. Mai 2025 um 20:46:26 UTC+2:
>>>>
>>>>> Dear all,
>>>>>
>>>>> I've been running a frequency calculation for over a month and it's 
>>>>> still running. I don't know what's wrong. Can someone help me?
>>>>> Best regards,
>>>>> Sihem
>>>>>
>>>>

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