[CP2K-user] [CP2K:21917] Re: Planar average potential along Z in &EXTERNAL_POTENTIAL

[xuan Garrett]

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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