Paolo, Thanks for looking into this.
> > Since the exchange-correlation energy depends on the modulus of the > magnetization, the theory is invariant with respect to its sign. Of > course > this is no longer true when one introduces an external magnetic field > and one has to take care to use a consistent convention. I believe there are two related but somewhat different issues here: one, as you say, is to make sure that a consistent convention is used for the sign of the magnetization and that of the magnetic field. For example, if one does an scf calculation on a non-magnetic system and specifies in the input file that the applied magnetic field is along +z, then at the end of the calculation the induced magnetization given in the output file should also be along +z. I did this exercise and it is fine. The second issue is whether the absolute (as opposed to relative) signs of both magnetic field and magnetization are correctly reported in the output file. One way to check that is to evaluate a third quantity which flips sign upon magnetization reversal, such as the anomalous Hall conductivity. As Ralph mentioned, changing signs all over the code can be tricky, but it is probably worthwhile to clarify the sign convention in the output file. Ralph suggested writing in the output "spin polarization" instead of "magnetic moment". My preference would be to report the magnetic moment (a more "physical" quantity), and reverse the sign of the actual number. This has the additional advantage of making it easier to add the orbital magnetization contribution, when its evaluation becomes feasible. Regards, Ivo -- --------------------------------------------------- Ivo Souza Department of Physics, Univ. of California Berkeley tel. +1.510.642.3597 fax +1.510.643.8497 isouza at berkeley.edu http://smilodon.berkeley.edu/ ---------------------------------------------------
