[CP2K-user] [CP2K:21918] Re: Planar average potential along Z in &EXTERNAL_POTENTIAL

[Ravi Kumar]

Hi Xuan,

Thanks for the clarification.

Yes, I also noticed that. I used  VALUES [eV] -0.2 [angstrom] 1.0  in order
to match with VASP/QE results.

Thank you very much for your kind help.

Best,
Ravi


On Sat, Oct 25, 2025 at 1:36 PM xuan Garrett <xwgarrett at gmail.com> wrote:

> Hi，Ravi，
> Yes，you got it. This example is also provided in the official website from
> cp2k，that is the summer school by Prof. Matt. You can check it.
>
> Be aware that the direction of this static field is opposite to the
> traditional definition.
>
> Best regards，
> Xuan
>
> Ravi Kumar <ravikumar381709 at gmail.com>于2025年10月25日 周六11:37写道：
>
>>
>> Hi xuan Garrett,
>>
>> Thanks a lot for the suggestion,  it works well now.
>>
>> I have one more question for clarification:
>> &EXTERNAL_POTENTIAL
>>     FUNCTION (A/B)*Z
>>     VALUES [eV] 0.2 [angstrom] 1.0
>>     PARAMETERS A B
>> &END EXTERNAL_POTENTIAL
>>
>> If I understand the notation correctly, the applied potential corresponds
>> to *0.2 V/Å* in the z-direction, right?
>>
>> Best,
>> Ravi
>>
>> On Friday, October 24, 2025 at 6:30:17 PM UTC+9 xuan Garrett wrote:
>>
>>> Hi，Ravi，
>>> Yes，the problem is that the potential applied by efield is not written
>>> in V_hartree，but in &PRINT External_field cube. Then you should connect the
>>> two cubes to obtain the saw-tooth potential.
>>> Best regards
>>> Xuan
>>>
>>> Ravi Kumar <ravikum... at gmail.com>于2025年10月24日 周五17:23写道：
>>>
>>>> Hi xuan Garrett,
>>>>
>>>> I am also interested in applying a saw-tooth potential, as done in
>>>> VASP, using CP2K and obtaining results similar to yours.
>>>> Were you able to achieve the expected results with CP2K?
>>>>
>>>> Best,
>>>> Ravi
>>>>
>>>> On Monday, March 3, 2025 at 4:50:18 AM UTC+9 Quentin Pessemesse wrote:
>>>>
>>>>> I am not sure if this line is correct:
>>>>> VALUES [eV] 0.2 [angstrom] 1.0
>>>>> According to the manual, you should define units in another line with
>>>>> the keyword "UNITS eV angstrom". Maybe either or both of your values is not
>>>>> being read correctly.
>>>>> Tell me if that works :)
>>>>> Best,
>>>>> Quentin
>>>>> Le mercredi 26 février 2025 à 06:11:46 UTC+1, xuan Garrett a écrit :
>>>>>
>>>>>> Dear cp2k,
>>>>>>
>>>>>> I am trying to deal with the planar average potential under static
>>>>>> electric field, which is realized by &EXTERNAL_POTENTIAL in &DFT section,
>>>>>> and the dipole correction is switched on:
>>>>>> SURFACE_DIPOLE_CORRECTION T
>>>>>> SURF_DIP_DIR Z
>>>>>> &EXTERNAL_POTENTIAL
>>>>>>     FUNCTION (A/B)*Z
>>>>>>     VALUES [eV] 0.2 [angstrom] 1.0
>>>>>>     PARAMETERS A B
>>>>>> &END EXTERNAL_POTENTIAL
>>>>>>
>>>>>> However, by checking the hartree.cube in the field of 0.2
>>>>>> eV/Angstrom, the saw-tooth potential is not observable, while in VASP, the
>>>>>> LOCPOT displays such saw-tooth potential.
>>>>>>
>>>>>> So, if there is the problem with such condition in CP2K? How to deal
>>>>>> with this?
>>>>>> [image: image.png][image: image.png]
>>>>>>
>>>>>> Best regards,
>>>>>> Xuan
>>>>>>
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