[Pw_forum] The symmetry of bands

[程迎春]

Dear pwscf users,
        I calculated band structure of  AlN considering spin-orbital
interaction.  Some published reports showed that considering spin-orbital
interaction the top of valence band is split into the Gamma7, Gamma9 and
Gamma7 states by crystal field and spin-orbital coupling (Appl. Phys. Lett.
83, 5163).  However, my calculated band structure is different from the
published one.  The following is the input files:
scf.in
&control
                    title = 2h_aln,
                      prefix = '2h_band',
                 calculation = 'scf' ,
                restart_mode = 'from_scratch' ,
                  wf_collect = .false. ,
                      outdir = './' ,
                      wfcdir = './' ,
                  pseudo_dir = './' ,
                     tstress = .true. ,
                     tprnfor = .true. ,
                   wf_collect = .true. ,
 /
 &SYSTEM
                       ibrav = 4,
                   celldm(1) = 5.904838149212,
                   celldm(3) = 1.603024550651,
                         nat = 4,
                        ntyp = 2,
                     ecutwfc = 80,
                       nosym = .false. ,
                     lspinorb = .true.,
                     noncolin= .true.,
                   starting_magnetization=0.00,
 /
 &ELECTRONS
            electron_maxstep = 100,
                    conv_thr = 1.D-12,
 /
ATOMIC_SPECIES
    N   14.00700  N.rel-pbe-rrkjus.UPF
   Al   26.98200  Al.rel-pbe-rrkj.UPF
ATOMIC_POSITIONS (crystal)
N        0.333333333   0.666666667   0.379371803
N        0.666666667   0.333333333   0.879371803
Al       0.333333333   0.666666667  -0.002269507
Al       0.666666667   0.333333333   0.497730493
K_POINTS automatic
  4 4 4   1 1 1
band.in
&control
                      title = 2h_aln,
                      prefix = '2h_band',
                 calculation = 'bands' ,
                restart_mode = 'from_scratch' ,
                  wf_collect = .false. ,
                      outdir = './' ,
                      wfcdir = './' ,
                  pseudo_dir = './' ,
 /
 &SYSTEM
                       ibrav = 4,
                   celldm(1) = 5.904838149212,
                   celldm(3) = 1.603024550651,
                         nat = 4,
                        ntyp = 2,
                     ecutwfc = 80,
                     occupations='fixed',
                     nbnd=30,
                         lspinorb = .true.,
                     noncolin= .true.,
                   starting_magnetization=0.00,
 /
 &ELECTRONS
            electron_maxstep = 100,
                    conv_thr = 1.D-12,
 /
ATOMIC_SPECIES
    N   14.00700  N.rel-pbe-rrkjus.UPF
   Al   26.98200  Al.rel-pbe-rrkj.UPF
ATOMIC_POSITIONS (crystal)
N        0.333333333   0.666666667   0.379371803
N        0.666666667   0.333333333   0.879371803
Al       0.333333333   0.666666667  -0.002269507
Al       0.666666667   0.333333333   0.497730493
K_POINTS
         1
  0.000000  0.000000  0.000000  1.00

bands.in for bands.x to get band symmetry information

&inputpp
prefix='2h_band'
outdir='./'
filband='spin.dat'
lsigma(3)=.true.
lsym=.true.
/
The calculated results of the band structure at Gamma point is as following:
spin.dat:
 &plot nbnd=  30, nks=   1 /
            0.000000  0.000000  0.000000
  -8.070  -8.070  -5.968  -5.968   1.092   1.092   6.154   6.154   6.169
6.169
   6.803   6.803   6.816   6.816   7.015   7.015  11.136  11.136  13.603
13.603
  17.513  17.513  18.094  18.094  18.118  18.118  19.967  19.967  20.042
20.042

spin.dat.rap:
 &plot_rap nbnd_rap=  30, nks_rap=   1 /
            0.000000  0.000000  0.000000    T
       1       2       5       6       5       6       5       6
3       4
       1       2       3       4       1       2       1       2
5       6
       5       6       1       2       3       4       1       2
5       6

My questions are:
1. Why the calculated top of valence bands (15th, and 16th ) do not split as
reported work (Appl. Phys. Lett.83,5163)?
2. In the spin.dat.rap file, what does the symbol "T" stand for?  And what
does the "1       2       5       6       5       6       5  ..." mean?

Thank you in advance!

-- 
Y. C. Cheng
Department of Physics
Nanjing University
Nanjing 210093
P. R. China
Tel: 86-25-83592907
Email: yccheng.nju at gmail.com
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