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## Main Question or Discussion Point

I have become fascinated by Topological Insulators (TI) and wish to learn more about them. I have successfully used a slab calculation to look at one of the prototypical TIs, Bi2Te3 using the LAPW+LO/APW+LO code Wien2K using a 4 quintuple layer slab. I can see the surface states across the gap, but I would like to go further and calculate the spin texture. While I understand the logic of finding the expectation values of Sx and Sy in a theoretical context, it is not clear to me how to calculate the field of expectation values in Wien2k. For example while the wavefunction can be save in the form of the expansion operators for the basis functions, the spinors are not there. In fact a polarization axis is specified in setting up a spin-orbit coupling calculation (case.inso), so it would appear that the spin quantization axis is specified. Does anyone have any idea how to get <Sx>, <Sy>, and or <Sz> from the code? Is it necessary to go into the guts of Wien2K and write a special module to calculate the spin expectation values (it will be a lot of work).

Cheers,

Paul

Cheers,

Paul