[Pw_forum] time-reversal symmetry broken

[Timo Thonhauser]

Dear All,

I have a question concerning the breaking of time-reversal symmetry
within PWscf. For my proposes I have modified the code and included a
(periodic) vector potential into the Hamiltonian. The code gives very
good results for the quantity that I am interested in for molecules,
i.e. gamma-point calculations. However, when I try to do calculations
for periodic solids, the results worsen.

I think the code (unless you do spin-orbit coupling) assumes time-
reversal symmetry. In principle, including a vector potential breaks
time-reversal symmetry. But, in the cases of my gamma-point calculations
that did not cause any problems ( psi_(-k)=psi_(k)* for k=gamma ) and
hence, I get good results for molecules. However, maybe this is the
problem with my calculations for extended systems: including the
vector potential breaks time-reversal symmetry, and
in general psi_(-k) is not psi_(k)*, but the code is not "aware"
that the symmetry has been broken.

Thus, my question is: is there a simple way to tell the code that
time-reversal symmetry is broken without getting into spin-orbit
stuff?

Thanks,
Timo Thonhauser, MIT

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Dr. TIMO THONHAUSER
Department of Materials Science and Engineering         (617) 253 6026
MIT, 13-4084, 77 Massachusetts Avenue               thonhauser at mit.edu
Cambridge, MA 02139-4307, USA                    www.mit.edu/~thonhaus
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