[Wannier] Relative phases of converged Wannier orbitals

[Nicola Marzari]

Dear Peyton, indeed, this is correct - in a supercell, you could end up 
with -1 for certain orbitals, but not for others, and doing e.g. a band 
interpolation would require fixing this by hand (for now).

				nicola



On 21/05/2019 18:38, Robert Peyton Cline wrote:
> Dear Wannier90 developers,
> 
> I have a question concerning the relative phases of the final Wannier 
> orbitals.  I've used Wannier90 for the past few years, and I feel quite 
> comfortable with the code and with how I've used it for my own research, 
> but I admit I am confused about one aspect of the final orbitals.  In 
> the Wannier90 papers, it is said that all of the final Wannier orbitals 
> are real up to a trivial global phase factor, assuming the global 
> minimum is reached.  In all of my simulations, I have verified this by 
> plotting my final MLWFs and investigating the maximum Im/Re values.  
> However, this statement does not seem to exclude the possibility that 
> the orbitals can end up with opposite signs -- e.g. some phase-like 
> prefactor, exp(-i*pi) = -1.  I am wondering if something like this might 
> happen because I am currently doing some post-processing calculations 
> where the sign of the wavefunction might matter, i.e. by influencing the 
> off-diagonal Hamiltonian matrix elements.  On the one hand, I feel like 
> the gauge transformation in the multiband formalism alleviates this 
> problem, but I am not entirely sure if that's true.  Any help on this 
> issue would be greatly appreciated.
> 
> Thank you,
> Peyton Cline
> 4th year PhD student
> Eaves Group
> CU-Boulder
> 
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-- 
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project