On Oct 10, 2008, at 3:58 AM, yumin qian wrote: > There is one problem I am not clear about DFPT in external > electronmagnetic field. How to switch on the external field since > the field will distroy the translational symmetry(periodic boundary > condition ).
please, take the time to have a glance at: S. Baroni, S. de Gironcoli, A. Dal Corso, and P. Giannozzi, Phonons and related crystal properties from density-functional perturbation theory, Rev. Mod. Phys. 73, 515 (2001). > > There a two way right now : one is add a dipole layer in vaccum > layers , this method can only be used in slab calculation > > the other is to add a periodic field and at the end make the > periodic to infinite (long wave appriximation). Vanderbilt also made > a proposal using the Berry phase approach, third, DFPT (restricted to the linear, or low-order) regime > My question is in PWSCF how the electronic field is added , through either of the first two methods. the third is implemented in PHONON > and whether the method can be used in metal system ? homogeneous electric fields in a metal? for that a computer code is not enough. One should modify Maxwell's equations! SB --- Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste http://www.sissa.it/~baroni / [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype) La morale est une logique de l'action comme la logique est une morale de la pens?e - Jean Piaget Please, if possible, don't send me MS Word or PowerPoint attachments Why? See: http://www.gnu.org/philosophy/no-word-attachments.html -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20081010/8ce30e18/attachment.htm