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Are there the forces on ions by ExternalElectricField?

Asked by Chao Lian

Dear Nick

In some packages I studied, e.g. quantum espresso, a system with external electric field include the field-ion interaction, besides the field-electron interaction. But I haven't yet find this kind of subroutines in SIESTA. Is it so or I miss something?

Thank you.

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Nick Papior (nickpapior) said : 		#1

Thanks for bringing this to our attention. I will check this and return to you.

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Nick Papior (nickpapior) said : 		#2

We have went through the code and asserted that the external electric field is included in the field-ion interaction. It does so via the saw-tooth potential which is added to the Hartree potential.
By comparing with other codes you may find direct calls for field-ion interactions, but that may be due to the fact that the saw-tooth potential isn't added in the Hartree potential. In such cases one is required to explicitly calculate the field-ion interaction.

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Chao Lian (charleslian) said : 		#3

Thanks, Nick, for your careful research and kind reply.

But this conclusion lead to another question : why additional electric-dipole energy term is manually added in SIESTA? Since sawtooth field is handled by changing the Hartree potential, the energy between electric field and the system has been naturally included already.

It may be not so important, you can totally ignore it if it do nothing to help :-)