EXTERNAL_POTENTIAL does not work with semi-empirical methods and SCC-DFTB

[Hang Xiao]

Hi,

I am trying to apply external electric field to semi-empirical or DFTB calculations. But it does not work. It seems the test system (a OH ion) does not feel the electric field. The input files are uploaded as attachment. Can you tell me what I'm doing wrong? 

Thank you.

Hang 

[Teodoro Laino]

simply.. they are not implemented.

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<Ion_NonP_NotWork.tar.gz>

[Xiao Hang]

Hi Teodoro,

Thank you for your quick reply. That's kind of pity that these functions are not implemented in CP2K. But I still have a question. Is it hard to implement or meaningless to do so (semi empirical methods are not suitable to deal with polarization induced by external electric field)?

Best,

Hang

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[Teodoro Laino]

it makes sense.. you can try to implement that.

[Xiao Hang]

Thank you. Maybe I will give it a try in future. 

[Matt W]

Hi,

As a short term fix you could probably get what you wanted out of the QMMM code by adding a series of charges that give you the field you want across the QM region. It will take a bit more experimenting with than just adding the external field as you hoped.

QMMM for DFTB has been recently implemented, I think. Any external potential implementation for SE or DFTB would probably be working in a similar spirit to the QMMM.

Matt

[Hang Xiao]

Thank you, Matt.

Using mm charges to generate the efield is such a good idea. I will give it a try. 

Best,

Hang 

[jts2t...@gmail.com]

Hi Matt,

 

I have been searching for this topic these days. I want to know how to use this functionality in cp2k if I need to know the response of the QM region to the external electric field. This may be the real problem if we want to simulate something happening in the physical world.

Expecting for your reply !

在 2015年2月12日星期四 UTC+8下午3:32:13，Matt W写道：