[CP2K:4719] dbcsr error when applying periodic efield

[Matt W]

Hi David,

On Friday, October 25, 2013 9:03:09 PM UTC+1, David Stelter wrote:
>
> Hi Matt,
>
> We have looked into EXTERNAL_POTENTIAL, some guidance on the section would 
> be appreciated! I've read on these forums that people have put an efield 
> value as a parameter in this section. How is this section treated? I want 
> to apply an efield, but shouldn't I be putting in a potential multiplied by 
> some distance of the periodic box?
>
>
in the DFT section

&EXTERNAL_POTENTIAL
    FUNCTION Z*(A/B)
    PARAMETERS A B
    VALUES [eV] 0.1 [angstrom] 1.0
&END

should add a field of 0.1 V/A along the Z direction of your QM cell. This 
is just a classic sawtooth potential - but as your QM region has vacuum 
around it there should be no issues.

As Flo notes for the periodic_efield, I think this will only act on the QM 
region. Adding a similar potential over the classical region would cause 
issues with periodicity. 

I haven't tried it in combination with ROKS or QMMM.

Maybe an easier solution is just to add some artificial charges into the MM 
region to generate the field? Though you'd have to take into account that 
their effect would get screened by solvent...

Matt

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