The ABINIT Users Mailing List ( CLOSED )

[zhangting <zhangting@pku.edu.cn>]

Hello everyone:

      In the ABINIT codes, the default unit of length is bohr, and the 
default unit of energy is hartree. However, in some output files, the default 
unit is unclear. For example, we are working on CsCl system, and got some 
*_POT file, _WFK file and _DEN files. Firstly we use cut3d code to transform 
such binary files to ASCII ones, with option 8(3D data with coordinates). 
Then we are puzzled what unit these files are using?
-----------------------------------------------------------------------------------
TITLE = "  "                                                                  
                     
VARIABLES = "X"  "Y" "Z" "DENSITY"                                            
                     
ZONE I=           40  J=           40  K=           40  F=POINT               
                     
  0.0000000000000000         0.000000000000000         0.000000000000000      
   -9.409566054466262 
  0.1046133241197124         0.000000000000000         0.000000000000000      
   -9.353364668879102 
  0.2092266482394249         0.000000000000000         0.000000000000000      
   -9.007323659586323 
-----------------------------------------------------------------------------------
This is a part of *_POT file, it seems that the coordinate points are listed 
in angstrom, because the cell parameter is 7.9076 bohr(or 4.18453 A), and the 
cell is divided by 40x40x40's FFT grid, so if the unit is A, the step length 
is perfectly correct. Now comes the question: what the unit is to describe 
the potential in the last column? hartree/bohr? or eV/A ? or something else? 
Here the code may using Angstrom as its default unit, so we are not sure what 
the units are for other values. The same questions can be asked in _WFK and 
_DEN files, please see:
-----------------------------------------------------------------------------------
    0.0000000000    0.0000000000    0.0000000000 -2.3396145885047890  
0.0000000000000000 
    0.1046133274    0.0000000000    0.0000000000 -2.2735996426805310 
-0.0000000000000001
    0.2092266548    0.0000000000    0.0000000000 -2.1343791154474720 
-0.0000000000000002
    0.3138399822    0.0000000000    0.0000000000 -2.0267382740339520 
-0.0000000000000005
-----------------------------------------------------------------------------------
This is part of a _WFK file, the real part and the imaginary part of the 
wavefunction are listed, however, what is its unit? in a _DEN file, what's 
the unit?

And also,in a phonon calculation, we can obtain phonon eigen-vectors. We have 
calculated CsCl's phonon eigenvectors, the resaults are like:
------------------------------------------------------------------
     Eigendisplacements                                       
 (will be given, for each mode : in cartesian coordinates
   for each atom the real part of the displacement vector,
   then the imaginary part of the displacement vector)
  Mode number    1   Energy    0.000000E+00
 Attention : low frequency mode.
   (Could be unstable or acoustic mode)
  1  0.00000000E+00  0.00000000E+00  1.80512183E-03
     0.00000000E+00  0.00000000E+00  0.00000000E+00
  2  0.00000000E+00  0.00000000E+00  1.80510280E-03
     0.00000000E+00  0.00000000E+00  0.00000000E+00 
    .....
 Mode number    4   Energy    4.681643E-04                
  1  0.00000000E+00  0.00000000E+00 -3.49501178E-03
     0.00000000E+00  0.00000000E+00  0.00000000E+00
  2  0.00000000E+00  0.00000000E+00  9.32308863E-04       
     0.00000000E+00  0.00000000E+00  0.00000000E+00      
    .....
------------------------------------------------------------------ 
Of the phonon eigenvector,What unit is it?

We don't know which unit are to represent the potential,the wavefunction, the 
electron-density and the phonon eigenvector, how to get such imformation from 
the files, and how to use other unit as default?

    Thanks!  



　　　　　　　　zhangting
　　　　　　　　zhangting@pku.edu.cn
　　　　　　　　　　2006-05-12