[Pw_forum] Re:error in q2r.out

[degironc]

I see two reasons why the number of q-point needed by ph.x could differ 
from the original one:
1) the symmetry of your crystal (the one relevant for the phonon calc.) 
is lower than the symmetry of your bravais lattice (the one generated by 
kpoints.x) ... use your q-points list as the k_points list in a scf 
calculation and see how many points pw.x generates... that
is the list you should use in the ph.x calculation. How many symmetry 
operations are found by pw.x in the opriginal scf calculation ?
Are you sure you provide enough digits in the atomic coordinates in 
order to have all expected symmetries ?
2) the test condition used to check whether two points are equivalent is 
tighter than the error due to truncation in the number of digits printed 
in the q-point list. This however would INCREASE the number of points 
not decrese its. In any case, to check this possibility you could modify 
kpoint.x so as to print a few more digits and see if this fix the problem.
let me know
stefano

wangjunjie1981_0 wrote:

> Dear stefano
> Thank you for your answer. you say the case I have noticed . As a 
> matter of fact the number of qpoints generating by kpoints.x is 64 
> .but I don't know why the number of qpoints calculating in q2r.out 
> becomes 58 .Can you tell me what the cause is . Thank you !
> my kpoints.x file is
>
> 12
> 1 0.0000000 0.0000000 0.0000000 1.00
> 2 0.2500000 0.1443376 0.0000000 6.00
> 3 0.5000000 0.2886751 0.0000000 3.00
> 4 0.2500000 0.4330127 0.0000000 6.00
> 5 0.0000000 0.0000000 0.2340828 2.00
> 6 0.2500000 0.1443376 0.2340828 12.00
> 7 0.5000000 0.2886751 0.2340828 6.00
> 8 0.2500000 0.4330127 0.2340828 12.00
> 9 0.0000000 0.0000000 0.4681655 1.00
> 10 0.2500000 0.1443376 0.4681655 6.00
> 11 0.5000000 0.2886751 0.4681655 3.00
> 12 0.2500000 04330127 0.4681655 6.00
>
>
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