[Wien] Deformation of Diamond

[Hui Wang]

Dear wien2k master:
    About questions last time, I adopted the suggestions of Kurt Lejaeghere, here are the new problems:
    (1)I changed the 8 atoms to C 1 , C 2,..........C 8, after the sgroup, it found:
=======================
Bravais lattice: Triclinic
     a             b            c
 6.70248100    6.70248100   6.70248100
     alpha         beta         gamma
 90.00000000    90.00000000   90.00000000
=========================
     and also there was nothing wrong with symetry, I used all the default setting parameters. Then to kgen:
===========================
inputfiles prepared (07:16:03)  
>   inputfiles for lapw1c/2c prepared, no inversion present     (07:16:03)  
>   kgen        (07:16:03)            1  symmetry operations without inversion
 inversion added (non-spinpolarized non-so calculation)
  NUMBER OF K-POINTS IN WHOLE CELL: (0 allows to specify 3 divisions of G)
10000
 length of reciprocal lattic vectors:   0.937   0.937   0.937  21.544  21.544  21.544
  Shift of k-mesh allowed. Do you want to shift: (0=no, 1=shift)
0
then I get 4631 kpoints in IBZ, too much compared to cubic symetry which only have 300 kpoints.
then  dstart -c I get 4698  FOURIER COEFFICIENTS CALCULATED UP TO GMIN, also too much compared to cubic symetry which only have 80 FOURIER COEFFICIENTS CALCULATED UP TO GMIN.
Here, my question are: Is there something wrong with the parameter ? I know symetry is very low, but are 4631 kpoints in IBZ and 4698 FOURIER COEFFICIENTS reasonable ? (I think this is too huge to calculate)
   
 
   (2)About the elastic constant, I konw when deform the structure will change the spacegroup, but it should depend on the size you deform. Here I just deformed 0.01 Ang in x axes, I don't think it will need a new spacegroup.
I also find S. Jalali. already answered this problem long time ago:
=================================
The elastic constants can be derived from  second derivatives of the total energy with respect to appropriate  deformations. The appropriate deformations are generalized coordinates which  can be lattice parameters or angles of the proper unit cells.
  For cubic structure, where the matrix representation of elastic tensors has  only 3 independent components, i.e.  C11, C12, C44=C66, you can use the  elast package of wien2k, http://www.wien2k.at/reg_user/textbooks/elast-UG.ps,  to calculate these constants.
  For other structure one must first find the proper deformations and plot E  versus them and then try to evaluate the second derivatives of the curves. 
  Regarding your second question, I can say that, density of states influences  not only the elastic constants, but also any other physical quantities. This is  the density of state that differs from one case to the others, and this is why  one case has different properties from the others. Density of states in the energy-space  plays an important role in materials, which can be compared to the role of  charge densities in the real (coordinate)-space.
  
  Your,
  S. Jalali.
=====================================
   Here, my questions are: the hyperlink is forbidden although I signed in with our account and password, I don't why ?  
   For cubic system, how to deform it by only 0.01 Angstron in x axes without changing the spacegroup?
 
   Any help will be appreicated:)
 
Hui 

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