[Pw_forum] Is there a way to fix the c of supercell and vary only a and b

[mohnish pandey]

Dear QE users,
                          I am doing supercell calculation for some systems.
But I want to change the a and b parameter for the supercell but want to fix
the c for that because the in plane lattice parameter(xy plane) should
change on relaxation process. Right now I am using 'vc-relax'  calculation
for the same. But many times its given error " Enough space not allocated to
fft grid". I am increasing the cell_factor to 1.8 which I think is very
large value and this also makes the relaxation computationally expensive.
Can anybody suggest a way to resolve it, I was thinking of the way to vary a
and b and fix the c.
Thanks a lot in advance.

-- 
Regards,
MOHNISH,
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Mohnish Pandey
Y6927262,4th Year dual degree student,
Department of Chemical Engineering,
IIT KANPUR, UP, INDIA
+919235721300
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