[Pw_forum] Silicon DOS issue

[Xufeng Wang]

Dear community,

I am unable to obtain the square root energy dependency of the bulk Silicon
conduction band DOS, despite using a fine k grid (100x100x100).

I expect the DOS near conduction band edge (below the second conduction
band of silicon) has a square root dependence with energy. I plotted out
the (DOS)^2 vs energy I obtained here: http://imgur.com/a/Wu07z

As you can see, (DOS)^2 vs. energy is not linear, meaning DOS is not having
a square root dependence with energy. Is this an known problem or am I
doing something wrong? Here is the nscf calculation input deck:

-------

 &control

    prefix='silicon',

    pseudo_dir='../pseudo/'

    outdir = './results',

    tstress=.false.,

    tprnfor=.false.,

    calculation = 'nscf',

    verbosity='high',

 /

 &system

    ibrav=  2, celldm(1) =10.2623466921, nat=  2, ntyp= 1,

    ecutwfc = 30.0, ecutrho=300.0, input_dft='PBE', nbnd = 8,

 /

 &electrons

    diagonalization = 'david',

    conv_thr = 1d-08,

    mixing_mode = 'plain',

    mixing_beta = 0.7,

 /

ATOMIC_SPECIES

 Si  28.086  Si.pbe-n-rrkjus_psl.0.1.UPF

ATOMIC_POSITIONS

 Si 0.00 0.00 0.00

 Si 0.25 0.25 0.25

K_POINTS automatic

 100 100 100 0 0 0
-------

Thanks!

Xufeng
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