[Pw_forum] Some questions about IFC from PWSCF

[john Bob]

Dear Stefano:

Thank you very much for the answers. I lernt much from those. In some
textbook the force constant matrix are
                  (   L       L' )
F                (               )
  alpha,beta (   K      K' )         L is the index of cells, K index of
different atoms.

(1) Can I rewrite the F_(alpha,beta)^(na,nb)(R) as
                   (   0       L'  )
F                (                )            while L' is L(a,b,c)
L(R)       ?
  alpha,beta (  na      nb )

(2) F_{alpha,beta} matrix is 3X3 matrix. And It acts like other two rank
tensor ( dielectric tensor, electric conductivity tensor) under symmetry
operations ?  The independent parameters can be decided by group theory ?
one for cubic system.

(3) I pick up the
" x  x   1  1
 2 1  1   x.xxxx "
lines
================
   1   1   1   1
   1   1   1   4.30811843056E-02
   2   1   1   1.49655475926E-02
   1   2   1   1
   1   1   1   0.00000000000E+00
   2   1   1   0.00000000000E+00
   1   3   1   1
   1   1   1   0.00000000000E+00
   2   1   1   0.00000000000E+00
   2   1   1   1
   1   1   1   0.00000000000E+00
   2   1   1   0.00000000000E+00
   2   2   1   1
   1   1   1   4.30811843056E-02
   2   1   1   2.68996333333E-03
   2   3   1   1
   1   1   1   0.00000000000E+00
   2   1   1   0.00000000000E+00
   3   1   1   1
   1   1   1   0.00000000000E+00
   2   1   1   0.00000000000E+00
   3   2   1   1
   1   1   1   0.00000000000E+00
   2   1   1   0.00000000000E+00
   3   3   1   1
   1   1   1   4.30811843056E-02
   2   1   1   2.68996333333E-03
==========================
why Fxx /=  Fyy = Fzz ?

I am sorry for my poor english. Also sorry for so many annoying question,
self-teaching is a hard and careful work.


Dr  Zhou Bo

Norhwest University Xi'an China
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