[Pw_forum] CNT unit cell vectors

[Mahmoud Hammouri]

Hi all,
I have problem for defining the lattice vectors of carbon nanotubes, I saw some examples for zigzag CNTs and they are using ibrav =6 with celldm(1)=31 and celldm(3)= 0.25 and in another file celldm(3)=0.1704 I'm really wonder why they did not define celldm(2)? Now, for more than one unit cell how celldm(3) would change.
In the descriptions of the pw.x input file, for Tetragonal P (st):
 celldm(3)=c/a and since c=1.42 and a=4.26 then celldm(3)=0.333 not 0.25 or 0.17 as others said!!!


Regards
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