Charged systems and periodic boundary conditions

[ivasan]

Dear All,

I am using abinit to study charge defects in semiconductors and I would like to know how to deal with charged systems and periodic boundary conditions (PBC). In particular, how to remove the interaction of a charged system with the replicas generated by the PBC, which are also charged.

I found that the Ewald summation is conventionally used for this purpose. Abinit provides the value of this summation as 'Ewald energy' in the report of the different components of the total free energy of the system.

Nevertheless, I found that this energy depends only on the atomic positions of the system, but not on its charge state, i.e. for a fixed atomic coordinates different charge states have the same Ewald energy. Hence it seems that this energy does not account for the charge interactions (is this right?).

Some works also refer to charge corrections as 'dipole corrections'. Nevertheless I found that dipole corrections were not implemented in abinit a year ago (http://forum.abinit.org/viewtopic.php?f=9&t=103).

I would appreciate any information about how to deal with the charge issue.

Thanks for you time.

Regards,

Iván