Dear Friends,
I have looked for the answer to my question on the internet and on research papers but have not find it.
Here is the question: the usual calculation of macroscopic electric polarization (of the electrons) uses the Berry connection of occupied bands published by Resta/Vanderbilt in 1994. that calculation did not include spin-orbit coupling(SO). I want to know how Abinit (or any other dft code) takes into account SO coupling. On a more fundamental level, is there is a modified berry connection-type formula that includes SO that i dont know about?
Any leads will be appreciated,
Best,
Abinit_champion