[CP2K-user] [CP2K:14991] What are the default units of hartree potential and electric field in cp2k?
Fangyong Yan
fyya... at gmail.com
Tue Mar 23 21:23:07 UTC 2021
Hi, Kai,
We havenot gotten an answer from cp2k developers, so it is still unclear.
Dear cp2k developers, what is the unit for the electric field in the
EFIELD_CUBE
<https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/EFIELD_CUBE.html>
file?
Thanks!
Fangyong
On Tue, Mar 23, 2021 at 5:02 PM Kaixuan Chen <kaix... at gmail.com> wrote:
> Hi Fangyong,
> Thanks a lot for the answer. That is really helpfule.
> Kai
>
> 在2021年3月22日星期一 UTC-7 下午3:24:45<fy... at gmail.com> 写道：
>
>> Hi, Kai,
>>
>> The electric field near the point charge, which is the nuclei, can be
>> very large.
>>
>> I think cp2k does use Hartree/Bohr, and for the large values, such as 10
>> Hartree/Bohr = 500 V/Angstrom, this may be due to the fact that the
>> eclectic field point is very close to the nuclei.
>>
>> For the unit, you can ask cp2k developer to confirm, but I think it is
>> Hartree/Bohr, and I also think 500 V/Angstrom is correct, when it is
>> close to the nuclei.
>>
>> Fangyong
>>
>> On Mon, Mar 22, 2021 at 4:34 PM Kaixuan Chen <ka... at gmail.com> wrote:
>>
>>> Dear Fangyong,
>>> Thank you very much for the response. The units for the numbers of the
>>> cube files (both potential and electric field) is exactly what I want to
>>> know. They are not stated, neither in the cp2k manual nor in the cube
>>> files. So I try to treat the numbers in a.u. units. For example, the
>>> electric field cube file shows that at some positions, the number is 10
>>> hartree/e/bohr if the a.u. unit is the correct one. I think it is really
>>> huge for electric field, isn't it?
>>> By the way, when I mean 50000 MV/cm, I think it is equal to 50000 (10E6
>>> V)/(10E8 Angstrom) = 500 V/Angstrom.
>>> Because 1 hartree/e/bohr = 5142.20652 MV/cm, correct?
>>> Any suggestion on what is the default unit?
>>> Best,
>>> Kai
>>>
>>> 在2021年3月22日星期一 UTC-7 下午12:03:03<fy... at gmail.com> 写道：
>>>
>>>> Hi, Kai,
>>>>
>>>> I think you mean 5GV/cm = 500 V/Angstrom.
>>>>
>>>> I think you may need to do integration to obtain the electric field,
>>>> because it is a cube file, so what is the unit for the numbers
>>>> of your cube file?
>>>>
>>>> Fangyong
>>>>
>>>> On Mon, Mar 22, 2021 at 2:25 PM Fangyong Yan <fy... at gmail.com> wrote:
>>>>
>>>>> Hi, Kai,
>>>>>
>>>>> 50000 MV/cm = 50 V / (10E8) Angstrom = 5E-7 V/Angstrom, which is a
>>>>> very very small electric field.
>>>>>
>>>>> Best,
>>>>>
>>>>> Fangyong
>>>>>
>>>>> On Mon, Mar 22, 2021 at 1:07 PM Kaixuan Chen <ka... at gmail.com>
>>>>> wrote:
>>>>>
>>>>>>
>>>>>> Dear all,
>>>>>> I have generated the cube files of hartree potential (CP2K_INPUT
>>>>>> <https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT.html> /
>>>>>> FORCE_EVAL
>>>>>> <https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL.html>
>>>>>> / DFT
>>>>>> <https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT.html>
>>>>>> / PRINT
>>>>>> <https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/PRINT.html>
>>>>>> / V_HARTREE_CUBE
>>>>>> <https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/V_HARTREE_CUBE.html>)
>>>>>> and electric field (CP2K_INPUT
>>>>>> <https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT.html> /
>>>>>> FORCE_EVAL
>>>>>> <https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL.html>
>>>>>> / DFT
>>>>>> <https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT.html>
>>>>>> / PRINT
>>>>>> <https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/PRINT.html>
>>>>>> / EFIELD_CUBE
>>>>>> <https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/EFIELD_CUBE.html>)
>>>>>> from cp2k. I don't see an explicit description on the units that are used
>>>>>> in these cube files. If I take the a.u. as the default unit (hartree/e for
>>>>>> potential, and hartree/e/bohr for electric field), the value seems pretty
>>>>>> large. For example, I study the single water molecule system. The largest
>>>>>> electric field at some density grid is 10~15 hartree/e/bohr, that is,
>>>>>> ~50000 MV/cm. Please correct me if I am wrong, but the value seems
>>>>>> unreasonable to me.
>>>>>> Any suggestion will be welcome, thanks in advance.
>>>>>> Best,
>>>>>> Kai
>>>>>>
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>>>>>>
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