[QE-users] Double x-coordinate in bands.x output

[Carl-Friedrich Schön]

Dear all,

I have calculated the band structure for Si with 8 atoms in the UC 
(conventional standard from MP) using QE6.4.

My input is:

/&control//
// calculation = 'bands'//
// prefix='Si_mp-149_conventional_standard'//
// tstress = .true.//
// tprnfor = .true.//
// pseudo_dir='/rwthfs/rz/cluster/home/cs825852/DFT/UPF_Ressources_NSCF/NC'//
// outdir='tmp'//
// disk_io='low'//
// wf_collect=.true.//
/// //
//&system//
// ibrav =0,//
// nat=8//
// ntyp=1//
// ecutwfc = 100//
// ecutrho = 400//
// occupations = 'fixed'//
// nbnd = 24//
/// //
//&electrons//
// mixing_beta = 0.2//
// conv_thr = 1.0d-10//
/// //
//ATOMIC_SPECIES//
//Si 28.086 Si.upf//
//ATOMIC_POSITIONS {crystal}//
//Si  0.25  0.75  0.25//
//Si  -0.0  -0.0  0.5//
//Si  0.25  0.25  0.75//
//Si  -0.0  0.5  0.0//
//Si  0.75  0.75  0.75//
//Si  0.5  0.0  0.0//
//Si  0.75  0.25  0.25//
//Si  0.5  0.5  0.5//
//CELL_PARAMETERS//
//10.334398  0.0  0.0//
//0.0  10.334398  0.0//
//0.0  0.0  10.334398//
//K_POINTS {crystal_b}//
//12//
//0.0  0.0  0.0  20.0//
//0.5  0.0  0.5  20.0//
//0.5  0.25  0.75  20.0//
//0.375  0.375  0.75  20.0//
//0.0  0.0  0.0  20.0//
//0.5  0.5  0.5  20.0//
//0.625  0.25  0.625  20.0//
//0.5  0.25  0.75  20.0//
//0.5  0.5  0.5  20.0//
//0.375  0.375  0.75  20.0//
//0.625  0.25  0.625  20.0//
//0.5  0.0  0.5  20.0/

My bands.x output however states:
//

/high-symmetry point:  0.0000 0.0000 0.0000   x coordinate   0.0000//
//     high-symmetry point:  0.5000 0.0000 0.5000   x coordinate   0.7071//
//     high-symmetry point:  0.5000 0.2500 0.7500   x coordinate   1.0607//
//     high-symmetry point:  0.3750 0.3750 0.7500   x coordinate   1.2374//
//     high-symmetry point:  0.0000 0.0000 0.0000   x coordinate   1.2374//
//     high-symmetry point:  0.5000 0.5000 0.5000   x coordinate   2.1035//
//     high-symmetry point:  0.6250 0.2500 0.6250   x coordinate   2.4096//
//     high-symmetry point:  0.5000 0.2500 0.7500   x coordinate   2.5864//
//     high-symmetry point:  0.5000 0.5000 0.5000   x coordinate   2.9400//
//     high-symmetry point:  0.3750 0.3750 0.7500   x coordinate   3.2462//
//     high-symmetry point:  0.6250 0.2500 0.6250   x coordinate   3.5524//
//     high-symmetry point:  0.5000 0.0000 0.5000   x coordinate   3.8585/

As you can see, the fourth and fifth KPoint have the same x coordinate, 
while they are not identical.

The .gnu output seems to state the correct energies, while the 
x-coordinate just stays identical for this range:

/    1.2198   -4.4150//
//    1.2286   -4.4160//
//    1.2374   -4.4163//
//    1.2374   -4.4466//
//    1.2374   -4.4594//
//    1.2374   -4.4544//
//    1.2374   -4.4316//
//    1.2374   -4.3909/

/..../

I had the same issue occur with Cu (mp-30).

While I have found some outputs with the same problem (?) online, it was 
the topic of the discussion.

Is this a bug, or am I missing/misunderstanding some intended behavior?

Thanks and best,

Carl-Friedrich Schön, PhD Student, RWTH Aachen
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