[Wien] why artificial lowering of symmetry changes the total energy?

[katrusiat]

Dear all,

I perform ferromagnetic (FM) (I make it FM by modifying the case.inst file accordingly) GGA+U calculations of the total energy of Cs2CuCl4, the compound with 4 equivalent magnetic Cu's in a unit cell. When I create an artificial unit cell of a lower symmetry with 2 inequivalent pairs of Cu's: Cu1 and Cu2, and again perform a FM GGA+U calculation, the total energy of the system is slightly different.

By lowering the symmetry I only add labels to Cu's making them inequivalent, and also the crystallographic axes are interchanged in the new unit cell. So, why after these seemingly harmless actions the total energy should change?

Thank you,
Kateryna Foyevtsova

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