Confusion: cation and anion move towards the same direction under an external electric field

[Tonys_Yu]

Hello Marcella,

     Thanks for your advice. Actually, I also tried the keywords EFIELD and 
PERIODIC_EFIELD as shown below:

      &EFIELD
       ENVELOP CONSTANT
       &CONSTANT_ENV
       &END CONSTANT_ENV      
       INTENSITY  0.00194468915    #1V/A=0.0194468915a.u.       
       POLARISATION 1 0 0         
      &END EFIELD
and 
      &PERIODIC_EFIELD
       INTENSITY  0.00194468915     #1V/A=0.0194468915a.u.
       POLARISATION 1 0 0         
      &END PERIODIC_EFIELD

    but I get an error "On entry to DLASCL parameter number  4 had an 
illegal value" and the same results that cation and anion move towards the 
same direction,respectively. Both are strange results. I think some 
inappropriate keywords and values may exist. Could you have any suggestion 
of my situation?
    By the way, my cp2k package is version 2.5. I'm checking for using the 
latest version.

Tonys Yu

在 2017年7月19日星期三 UTC+8下午6:32:48，Marcella Iannuzzi写道：
>
> Hi,
>
> this external potential is not an electric field, it is just a linear 
> potential.
> Check the keywords EFIELD and PERIODIC_EFIELD.
>
> Marcella
>
> On Wednesday, July 19, 2017 at 12:20:54 PM UTC+2, Tonys_Yu wrote:
>>
>> Hello,
>>        I want to study a ionic displacement in a bulk water box with 30 
>> water molecules. External electric field is 0.1V/A, and added by 
>> EXTERNAL_POTENTIAL command as below:
>>
>>       &EXTERNAL_POTENTIAL
>>        FUNCTION (A/B)*X
>>        PARAMETERS A B
>>        VALUES [eV] 1.0 [angstrom] 10.0
>>       &END EXTERNAL_POTENTIAL
>>
>>     What makes me confused is that both water molecules and K-ion are 
>> moving along the negative direction of X. Moreover, when I changed the 
>> K-ion by a Cl-ion or reduced the electric field to a smaller value 
>> (0.001V/A), the same results was observed. It seems contrary to the fact 
>> that, with the same electric field (value and direction), K-ion and Cl-ion 
>> would move towards opposite directions. 
>>     I beg someone could shed light on my confusion. Necessary files have 
>> been attached.
>>
>> Tonys Yu
>>
>
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