The ABINIT Users Mailing List ( CLOSED )

[Fabien Bruneval <fabien.bruneval@polytechnique.fr>]

Dear Bo Liu,
the k-point where you want to calculate the GW energy has to belong to 
your k-point set in the full Brillouin zone. As you can see Z point 0. 
0. 0.5 is not one the 64 k-points generated by your Monkhorst-Pack grid 
4 4 4 shifted 0.5 0.5 0.5, as written out at the end of the output file.
I advise you to use instead the 4 4 4 grid but NOT shifted: just specify

shiftk 0. 0. 0.

This will create a k-point grid a bit larger (in the irreducible BZ), 
that contains (I bet) the Gamma point, Z point and other high symmetry 
points...
Good luck

Fabien Bruneval


lbo@ustc.edu wrote:

> Dear ABINIT experts,
>
> I have difficulty in GW calculation for correction of band gap .
> I an not sure how to set the parameters in GW calculation.
> I appreciate for any help!
>
>
> I have done the band structure calculation for PbFCl. 
> The result shows the direct gap at Z point in BZ. 
> The toppest valence band is 28 and the lowest conduction band is 29.
> I would like to using GW calculation the correction of the band gap between the 
> band of 28 and 29.
> I consulted the example for the case of Si given by the program.
>
> My input files is following:
>
> #Definition of the unit cell
> acell 7.841 7.841 13.81       
> rprim 1.0  0.0  0.0   
>      0.0  1.0  0.0  
>      0.0  0.0  1.0   
>
> #Definition of the atom types
> ntypat 3         
> znucl 9 17 82         
>        
> #Definition of the atoms
> natom 6           
> typat 1 1 2 2 3 3       
> xred                 
>                     
>   0.0   0.0   0.0
>   0.5   0.5   0.0
>   0.0   0.5   0.65
>   0.5   0.0   0.35 
>   0.0   0.5   0.2 
>   0.5   0.0   0.8   
>
> #Definition of the planewave basis set
> ecut  15.0         
>
> # Definition of the SCF procedure
> nstep   30      
> toldfe 1.0d-6
> diemac  12.0      
>
> # Definition of the k-point grid
> kptopt 1         
>                  
> nkpt 6
> ngkpt  4 4 4        
> nshiftk  1        
>                  
> shiftk 0.5 0.5 0.5
>
>                  
> # Definition of parameters for the calculation of the KSS file
> nband   35         
> nbndsto -1      
> ncomsto 0         
>
> ndtset      3
>
> # Calculation of the screening (epsilon^-1 matrix)
> optdriver2  3      
> getkss2     -1       
> nband2      35      
> npwwfn2     85       
> npweps2     169     
> plasfrq2    16.7 eV  
>
> # Calculation of the Self-Energy matrix elements (GW corrections)
> optdriver3  4        
> getkss3     -2       
> geteps3     -1       
> nband3      100      
> npwwfn3     133      
> npwmat3     169      
>                    
> ngwpt3      1               
> kptgw3                      
>  0.0   0.000    0.500  # Z point      
> bdgw3       28 29            
> zcut3       0.1 eV           
>
> The log file shows an error as below
>
> identifying k-points
> number of k-points in irreducible wedge (IBZ)   6
> k-points [reciprocal lattice units]          weights
>  1    0.125000    0.125000    0.125000       0.500000
>  2    0.375000    0.125000    0.125000       1.000000
>  3    0.375000    0.375000    0.125000       0.500000
>  4    0.125000    0.125000    0.375000       0.500000
>  5    0.375000    0.125000    0.375000       1.000000
>  6    0.375000    0.375000    0.375000       0.500000
> together with the  8 symmetry operations and inversion
> have yielded   64 k-points in Brillouin Zone (BZ):
>    1 0.125 0.125 0.125  0.125-0.125 0.125 -0.125-0.125 0.125 -0.125 0.125 
> 0.125
>    5-0.125-0.125-0.125 -0.125 0.125-0.125  0.125 0.125-0.125  
> 0.125-0.125-0.125
>    9 0.375 0.125 0.125  0.375-0.125 0.125 -0.375-0.125 0.125 -0.375 0.125 
> 0.125
>   13-0.125-0.375-0.125 -0.125 0.375-0.125  0.125 0.375-0.125  
> 0.125-0.375-0.125
>   17-0.375-0.125-0.125 -0.375 0.125-0.125  0.375 0.125-0.125  
> 0.375-0.125-0.125
>   21 0.125 0.375 0.125  0.125-0.375 0.125 -0.125-0.375 0.125 -0.125 0.375 
> 0.125
>   25 0.375 0.375 0.125  0.375-0.375 0.125 -0.375-0.375 0.125 -0.375 0.375 
> 0.125
>   29-0.375-0.375-0.125 -0.375 0.375-0.125  0.375 0.375-0.125  
> 0.375-0.375-0.125
>   33 0.125 0.125 0.375  0.125-0.125 0.375 -0.125-0.125 0.375 -0.125 0.125 
> 0.375
>   37-0.125-0.125-0.375 -0.125 0.125-0.375  0.125 0.125-0.375  
> 0.125-0.125-0.375
>   41 0.375 0.125 0.375  0.375-0.125 0.375 -0.375-0.125 0.375 -0.375 0.125 
> 0.375
>   45-0.125-0.375-0.375 -0.125 0.375-0.375  0.125 0.375-0.375  
> 0.125-0.375-0.375
>   49-0.375-0.125-0.375 -0.375 0.125-0.375  0.375 0.125-0.375  
> 0.375-0.125-0.375
>   53 0.125 0.375 0.375  0.125-0.375 0.375 -0.125-0.375 0.375 -0.125 0.375 
> 0.375
>   57 0.375 0.375 0.375  0.375-0.375 0.375 -0.375-0.375 0.375 -0.375 0.375 
> 0.375
>   61-0.375-0.375-0.375 -0.375 0.375-0.375  0.375 0.375-0.375  
> 0.375-0.375-0.375
>
> timing point number   50
> -cpu time  =       1.17 seconds
> -real time =       1.17 seconds
>
> check if the k-points for sigma are in the set of BZ
> **error findk 1: k-point not in the set of kbz;
>
>
> I wonder how to change the input parameters.
> Thank you very much for any help!
>
> sincerely
> Bo Liu
> lbo@ustc.edu
>
>
>