问：我计算的DOS图只有价带底上，即能量最低的几个能级有图形，费米能级附近及以上都没有，怎么回事？

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Sunforever

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Apr 1, 2009, 11:51:26 PM4/1/09

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问：我计算的DOS图只有价带底上，即能量最低的几个能级有图形，费米能级附近及以上都没有，怎么回事？
       输入文件节选如下：

&control

calculation='nscf'

restart_mode='from_scratch',

pseudo_dir ='/home/sunforever/espresso-4.0.4/pseudo',

outdir='./'

prefix='C'

/

&system

ibrav=4, a=6.49854, c=5.20544, nat=16, ntyp=3,

nspin = 2,

starting_magnetization(1)=0.7,

starting_magnetization(2)=0.5,

starting_magnetization(3)=0.3,

ecutwfc = 24.0, nbnd=8,

occupations='tetrahedra' ,

/

&electrons

diagonalization='david'

conv_thr = 1.0e-6

/

&IONS

ion_dynamics='bfgs',

pot_extrapolation = "second_order",

wfc_extrapolation = "second_order",

/

ATOMIC_SPECIES

C 12.011 C.pbe-van_ak.UPF

O 15.9994 O.pbe-van_ak.UPF

Zn 65.38 Zn.pbe-van.UPF

ATOMIC_POSITIONS (crystal)

O 0.165790870 0.331581739 0.384488756

.........................

其中，occupations='tetrahedra' ,这一项这样填会报错

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

     from tweights : error #         1

     bad Fermi energy

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

     stopping ...

这个参数不填会得到如下图形（见附件）
只有-20～-1eV左右的能级有图形后面的就是0了
请问这是为什么？

C.jpg

Sunforever

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Apr 1, 2009, 11:54:45 PM4/1/09

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问题在于nbnd＝8这个参数
默认情况下PWscf会自动计算价带和价带以上20％的能带的态密度
设定为8以后能带数太少
软件就由低往高算完为止
于是只有最低的几个能级有数据
删掉nbnd或把值设大一点应该就好了

感谢缪老师和姚洁的指点！

On 4月2日, 上午11时51分, Sunforever <cscguoch...@gmail.com> wrote:
> 问：我计算的DOS图只有价带底上，即能量最低的几个能级有图形，费米能级附近及以上都没有，怎么回事？
> 输入文件节选如下：
>
> &control
>
> calculation='nscf'
>
> restart_mode='from_scratch',
>
> pseudo_dir ='/home/sunforever/espresso-4.0.4/pseudo',
>
> outdir='./'
>
> prefix='C'
>
> /
>
> &system
>
> ibrav=4, a=6.49854, c=5.20544, nat=16, ntyp=3,
>
> nspin = 2,
>
> starting_magnetization(1)=0.7,
>
> starting_magnetization(2)=0.5,
>
> starting_magnetization(3)=0.3,
>
> ecutwfc = 24.0, nbnd=8,
>

> *occupations='tetrahedra' ,*

>
> /
>
> &electrons
>
> diagonalization='david'
>
> conv_thr = 1.0e-6
>
> /
>
> &IONS
>
> ion_dynamics='bfgs',
>
> pot_extrapolation = "second_order",
>
> wfc_extrapolation = "second_order",
>
> /
>
> ATOMIC_SPECIES
>
> C 12.011 C.pbe-van_ak.UPF
>
> O 15.9994 O.pbe-van_ak.UPF
>
> Zn 65.38 Zn.pbe-van.UPF
>
> ATOMIC_POSITIONS (crystal)
>
> O 0.165790870 0.331581739 0.384488756
>
> .........................
>
> 其中，occupations='tetrahedra' ,这一项这样填会报错
>
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
> from tweights : error # 1
>
> bad Fermi energy
>
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>

> stopping ...*

>
> 这个参数不填会得到如下图形（见附件）
> 只有-20～-1eV左右的能级有图形后面的就是0了
> 请问这是为什么？
>