[gpaw-users] wannier.py : Wannier functions not orthonormal

[Ravindra Shinde]

Hi All,
  I am adding a module to GPAW which requires calculations of Wannier
functions. I am using wannier.py to store them into cube files. These
functions will be read and tested for orthonormality. However, I found that
the overlap matrix of these functions is not identity.
  Following are the input files which can reproduce the results and the
added function (to the wannier.py) which calculates the overlap matrix.

    def wannier_overlap_matrix(self, calc):
        """ This function computes the overlap between Wannier orbitals
stored on the grid """

        centers = self.get_centers()
        num_wann = np.shape(centers)[0]
        overlap = np.zeros((num_wann, num_wann))

        for i in range(num_wann):
            for j in range(i,num_wann):
                wann_i = self.get_function(calc, i, pad=False)
                wann_j = self.get_function(calc, j, pad=False)
                overlap[i][j] =
(calc.wfs.gd.dv*Bohr**3)*np.sum(wann_i*wann_j)

        overlap_matrix = np.transpose(overlap) + overlap
        overlap_matrix[np.diag_indices_from(overlap_matrix)] /= 2.0

        np.savetxt("overlap_matrix.txt", (overlap_matrix), fmt='%8.6f',
delimiter=' ', newline='\n', header='Overlap Matrix', comments='# Ravindra
::  ', encoding=None)
        return

Best regards,

*Ravindra Shinde, Ph.D.*
Department of Chemical and Environmental Engineering
University of California, Riverside
Email: ravindra.shinde at ucr.edu
Phone: +1(951) 466-8168
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