[QE-users] Probable bug in additional_kpoints.f90 subroutine

[Prasenjit Ghosh]

Dear Lorenzo and others,

I think there is a bug in the above subroutine when either nqx1, nqx2 and
nqx3, or all of them are greater than 1. The example does not work with the
original version of the code because a lot of k-points with coordinates
(0,0,0 are generated as shown below:

        k(    1) = (  -0.2500000   0.2500000   0.2500000), wk =   0.5000000
        k(    2) = (   0.2500000  -0.2500000   0.7500000), wk =   1.5000000
        k(    3) = (   0.0000000   0.0000000   0.0000000), wk =   0.0000000
        k(    4) = (   0.0000000   0.0000000   0.0000000), wk =   0.0000000
        k(    5) = (   0.0000000   0.0000000   0.0000000), wk =   0.0000000
        k(    6) = (   0.0000000   0.0000000   0.0000000), wk =   0.0000000
        k(    7) = (   0.0000000   0.0000000   0.0000000), wk =   0.0000000
        k(    8) = (   0.0000000   0.0000000   0.0000000), wk =   0.0000000
        k(    9) = (   0.5000000   0.5000000   0.5000000), wk =   0.0000000

In the above list, k-points #3 to #7 are all (0, 0,0). Because of this,
when running the bands.x code, it complains and stops.

I was working with QE-6.8. The same problem I think persists also in 7.0.

In line 89 of the subroutine, the value of the counter 'iq' seems to be
wrongly initialized. With this the array elements are wrongly assigned in
xk(:,ik). The correct one should be:

iq=nkstot_old

Further the array elements of 'wk', corresponding to the additional
k-points also need to be set to zero. This can be done right after line 98
by adding the following line:
wk(iq)=0.0d0

The modified subroutine is attached.

With regards,
Prasenjit


With regards,
Prasenjit
-- 
PRASENJIT GHOSH,
IISER Pune,
Dr. Homi Bhabha Road, Pashan
Pune, Maharashtra 411008, India

Phone: +91 (20) 2590 8203
Fax: +91 (20) 2589 9790
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