Dear PWSCF users, I have a question regarding real band structure calculated from PWCOND. Complex band code requires kx,ky and E as input and gives kz as output. I have noticed that the answer for kz depends whether you have unit cell vectors as (a1,a2,a3) or (a1,a2,-a3). I did a calculation for Cu(001) with 2 atoms tetragonal unit cell, with the following input file -
& control calculation='scf' pseudo_dir = '/home/manoj/espresso-4.0.1/pseudo', outdir='./', prefix='cu', / &system ibrav = 0, celldm(1)=4.7588286373854648 nat= 2, ntyp= 1, ecutwfc =150.0, occupations='smearing', smearing='gaussian', degauss=0.02, ecutrho=400 / &electrons conv_thr = 1.0e-8 mixing_beta=0.7 / ATOMIC_SPECIES Cu 63.55 Cu.pz-d-rrkjus.UPF ATOMIC_POSITIONS Cu 0.0 0.0 0.0 Cu 0.5 0.5 0.707106781 K_POINTS (automatic) 8 8 8 1 1 1 CELL_PARAMETERS 1.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 1.414213562 &inputcond outdir='./' prefixl='cu' band_file ='bands.cu' ikind=0 energy0=2.d0 denergy=-0.5 ewind=104.d0 epsproj=1.d-6 / 1 0.0 0.0 1.0 24 This gives me reasonable answer and it matches up with existing results. Now when I changed a3 to -a3, so that the unit cell now has become (a1,a2,-a3), the answer does not match up with the previous one. Just to give you one concrete example- at Fermi energy for kx,ky (0,0) for unit cell (a1,a2,a3) we get kz=-0.1571 while for (a1,a2,-a3) we get kz=0.07323. I understand that for two different set of unit cell vectors we should not in general expect k_z to match, but this is a very special example, as it is just mirror symmetry about xy plane. so shouldn't kz in one set have value -kz in other? Thanks for your attention. Regards, Manoj Srivastava Department of Physics University of Florida Gainesville, FL