[Pw_forum] Can anyone help me explain what do the terms in *.fc file means?

[Zhen Huang]

Dear PW_SCFers,

If you use q2r.x command to calculate IFC's in real space and the output file is 
gra.fc. What does the output mean in the gra.fc file.

for example:

T  (what does T mean)
     13.7429076      0.0000000      0.0000000
      0.0000000     13.7429076      0.0000000
      0.0000000      0.0000000     13.7429076
    (what does this 3 by 3 matrix represent)
    1
      2.5582694      0.0000000      0.0000000
      0.0000000      2.5582694      0.0000000
      0.0000000      0.0000000      2.5582694
    2
     -2.5582694      0.0000000      0.0000000
      0.0000000     -2.5582694      0.0000000
      0.0000000      0.0000000     -2.5582694
   4   4   4 
   1   1   1   1 (what do the indexes represent? 1 for what)
   1   1   1   2.24617477868E-01 (what is this value and in what unit?)
   2   1   1  -6.30036204778E-03
   3   1   1   3.67142905560E-05
   4   1   1  -6.30036204778E-03
   1   2   1   1.16235628668E-02
   2   2   1  -5.93301773304E-04
   3   2   1  -2.47983120458E-04
   4   2   1  -6.30036204778E-03
   1   3   1   4.15237248762E-03
   2   3   1  -5.93301773304E-04
   3   3   1   3.67142905560E-05
   4   3   1  -5.93301773304E-04
   1   4   1   1.16235628668E-02
   2   4   1  -6.30036204778E-03
   3   4   1  -2.47983120458E-04
   4   4   1  -5.93301773304E-04
   1   1   2  -6.30036204778E-03
---------------
Zhen Huang
Ph.D. Student
Nanoscale Transport Research Group
School of Mechanical Engineering
Purdue University 
Tel: 765 426 9302