BornEffectiveCharge does not support calculators with spin type Noncollinear

[korand]

Hi dear friends,

I apply noncollinear spin orbit setting to evaluate dielectric tensor of topological insulator material like Bi2Se3. However, at the end of the simulation I encounter with the following note in log file:

NL.ComputerScienceUtilities.Exceptions.NLValueError: BornEffectiveCharge currently does not support calculators with spin type Noncollinear or SpinOrbit.

Similar to the tutorial I use two calculators, where the first one is used as initial spin for second one.

Best regards,
Korand

[Anders Blom]

This is not implemented, and I am not even sure it's possible to do so. It seems the common approach is to compute the Born charges without spin-orbit included, even for spin applications, the assumption being that the Born charges themselves are not strongly sensitive to the inclusion of spin or not. Of course that assumption is hard to prove, if you cannot compute the charges with spin-orbit and check, but it is a reasonable one plus the Born charges are extremely to compute accurately anyway, the error estimates are often 10-20%, thus a few extra percent do not really matter. See e.g. https://arxiv.org/pdf/1207.2916 and https://arxiv.org/pdf/0906.3803.pdf