[Wannier] Wannier functions of Cmc21 phase of Hydrogen

[Vahid Askarpour]

Dear Wannier Users,

In an attempt to generate the Wannier functions of the Cmc21 phase of hydrogen 
at 100GPa (already published in PRB 62, 15505, 2000), I relaxed the structure 
(with ABINIT) using LDA psp with a cut off energy of 60Ha and a 11x11x11 k-grid 
(convergence tests were done). The unit cell parameters are:

acell (Bohr)  3.5802517040E+00  3.5802517040E+00  5.6948406845E+00

rprim    4.9609471480E-01  8.6826841123E-01  0.0000000000E+00
           -4.9609471480E-01  8.6826841123E-01  0.0000000000E+00
           0.0000000000E+00  0.0000000000E+00  1.0000000000E+00

xred (reduced coordinates)
2.5121514893E-01  2.5121514893E-01  5.7250684394E-01
8.5213973344E-02  8.5213973344E-02  4.2749315606E-01
7.4878485107E-01  7.4878485107E-01  7.2506843938E-02
9.1478602666E-01  9.1478602666E-01  9.2749315606E-01

The structure is insulating with Fermi level at 2.83eV. With 4 atoms in the 
primitive cell, two bands are fully occupied. My wannier90.win is:

num_wann 2        !(since two bands are occupied)
dis_win_max 3.5 !(only the two occupied states are in this window)
num_iter 10000
dis_num_iter 10000
dis_conv_tol 1.0E-10
iprint 1
wannier_plot =true
wannier_plot_format=xcrysden
wannier_plot_supercell=3
Begin Projections ! (Using two of the atoms as starting point)
random
f= 8.5213973344E-02,  8.5213973344E-02,  4.2749315606E-01 : l=0
f= 7.4878485107E-01,  7.4878485107E-01,  7.2506843938E-02 : l=0
End Projections

However, after 10,000 iterations, I get the following in the output:

 Cycle:  10000
  WF centre and spread    1  ( -0.118897, -0.090041,  0.151445 )    17.92856764
  WF centre and spread    2  ( -0.023007, -0.110858,  0.105187 )    19.60921540
  Sum of centres and spreads ( -0.141904, -0.200898,  0.256632 )    37.53778304
  10000     0.102E+00     4.0933874374       37.5377830446     432.59  <-- CONV
  O_D=     21.7668345 O_OD=     14.1241376 O_TOT=     37.5377830 <-- SPRD
 Delta: O_D=  0.1058381E+00 O_OD= -0.4324867E-02 O_TOT=  0.1015132E+00 <-- DLTA
 ------------------------------------------------------------------------------
 Writing checkpoint file wannier90.chk... done
 Final State
  WF centre and spread    1  ( -0.118897, -0.090041,  0.151445 )    17.92856764
  WF centre and spread    2  ( -0.023007, -0.110858,  0.105187 )    19.60921540
  Sum of centres and spreads ( -0.141904, -0.200898,  0.256632 )    37.53778304
         Spreads (Ang^2)       Omega I      =     1.646810960
 ===============       Omega D      =    21.766834519
                                         Omega OD     =    14.124137566
  Final Spread (Ang^2)       Omega Total  =    37.537783045

      Wannier Function Num:    1       Maximum Im/Re Ratio =   18.718258
      Wannier Function Num:    2       Maximum Im/Re Ratio =   51.325554


The two Wannier functions are not real and the spread is large.  Is this output 
reasonable or am I missing something? Is there a way to lower the spread and 
make the functions real?

I'd appreciate your input.

Regards,

Vahid Askarpour
Physics Department
Dalhousie University
Halifax, Nova Scotia
Canada


      
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