Dear all, I was trying to compute macroscopic polarization in BaTiO3 (in both cubic and tetragonal phases), using Berry phase method and noticed the strange thing - in the cubic phase polarization is different along different directions:
siesta: Macroscopic polarization per unit cell (Debye): siesta: Along the lattice vectors 229.476838 267.720403 267.719074 siesta: Along cartesian directions 229.476850 267.720407 267.719158 Why is that? I was expecting that polarization should be identical, since this is a cubic phase. This result is not affected by cutoff or k-point sampling. Thanks, Sergey
