[Pw_forum] nonzero dos at Fermi level

[Stefano de Gironcoli]

the gaussian smearing contribution is non-zero hence your system is not 
an insulator but has a non-zero DOS at the Fermi energy.
are you sure that the structure is ok?
I dont know why it is so and why the integrated  dos around EF does not 
equal nelec... how is your input for the dos ? are you using the same 
number of points and the same smearing width ?

stefanno



Nguyen Doan Sau wrote:
> Hi there, 
> I have a problem related to DOS at fermi level. Let me start with my scf file first
> -------------
>  &system
>     ibrav=0, celldm(1)=0 , nat=22, ntyp=4,
>       ecutwfc =37.0, occupations='smearing', smearing='gauss', degauss=0.01, nelec=156
>     nspin= 1,
>  /
>  &electrons
>   electron_maxstep= 300
>     mixing_mode = 'plain'
>     mixing_beta = 0.2
>     conv_thr =  1.0d-6
>     diagonalization= 'david'
>  /
> --------------
> My pseudopotentials are norm conversing, which are generated by  ld1.x and their transferability is OK.
> here is the output
> ----------
> the Fermi energy is     3.4391 ev
>
> !    total energy              =   -1213.21835062 Ry
>      Harris-Foulkes estimate   =   -1213.21835085 Ry
>      estimated scf accuracy    <       0.00000034 Ry
>
>      The total energy is the sum of the following terms:
>
>      one-electron contribution =    -711.80653324 Ry
>      hartree contribution      =     352.57845405 Ry
>      xc contribution           =    -222.78424774 Ry
>      ewald contribution        =    -631.18916691 Ry
>      smearing contrib. (-TS)   =      -0.01685678 Ry
>
>      convergence has been achieved in  32 iterations
> ----------------------
> and Dos
> 3.000  0.2551E+02  0.1178E+03
>   3.100  0.2931E+02  0.1207E+03
>   3.200  0.3391E+02  0.1241E+03
>   3.300  0.3375E+02  0.1275E+03
>   3.400  0.2724E+02  0.1302E+03
>   3.500  0.2299E+02  0.1325E+03
>   3.600  0.2335E+02  0.1348E+03
>   3.700  0.2043E+02  0.1369E+03
>   3.800  0.1297E+02  0.1381E+03
>   3.900  0.9369E+01  0.1391E+03
>   4.000  0.8969E+01  0.1400E+03
>
> --------------
> My question are concerned to:
> + DOS is still not zero at fermi level E=3.4391
> + Integrated DOS is not equal number of electron (156) , even I try DeltaE=0.001
> -------------
> I have thought about the question
> +First, My compound is insulator, an oxide with optical bandgap of 4 eV. But in scf input, I use occupations='smearing'. Shoud I change it to occupations='fixed' and increase nbnd>156/2 and delete smearing variable.
> ------------
> Is there anyone had this problem before and please help me to fix that.
>
> Sau Nguyen
> U of Houston
>
>
>
>
>   
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