> http://www.democritos.it/pipermail/pw_forum/2008-August/009764.html
>
> http://www.democritos.it/pipermail/pw_forum/2008-August/009771.html
>
>>By definition: the Fermi energy is an energy which separates the valence
>>(occupied) electrons from the >>conductivity (unoccupied) electrons.
>>In our DFT calculations there is no "real" Fermi energy (E_F), only the one
>>for which \int_{E_min}^{E_F)N(E)dE = >>N is fulfilled (N(E) is the DOS, N is
>>total number of valence electrons).
?Because the DOS in the bandgap is 0, we can put the Fermi level everywhere in
the bandgap. Thus, following this?definition (?\int_{E_min}^{E_F)N(E)dE = N),
we can have many (or infinite number of solution for Fermi level). But when
using the code, there is only one value. I check DOS results.?I see the Fermi
level laying near the conduction band and It can be layed near the valance
band. I wonder what is the critical of choosing Fermi level in Pwscf algorithm?
By?the way,?Fermi level is? equal to?the chemical potential?at?0K. So, It is a
very important physical meaning and?it must be a specific value at 0K?in metal,
semiconductor and insulator.?Does choosing any value of Fermi level?in the
bandgap lose?its physical meaning??
I?post the input file of my calculation. It?shows?Fermi level moving around?in
the bandgap.
Model 1: C8O
&CONTROL
????? calculation = 'nscf',
????? prefix='C8O_LDA',
????? restart_mode = 'restart',
????? pseudo_dir ='./',
????? outdir='./'
????? tstress = .true. ,
????? tprnfor = .true. ,
????? nstep =? 100? ,
????? etot_conv_thr = 1.0E-4 ,
????? forc_conv_thr = 1.0D-3 ,
????? dt = 20 ,
/
&SYSTEM
????? ibrav= 4,? celldm(1) = 9.4518, celldm(3)=2, nat = 9, ntyp = 2, nspin=2,
????? ecutwfc =20, ecutrho = 210, occupations='tetrahedra',
????? starting_magnetization(1) = 0.0,
????? starting_magnetization(2) = 0.3,
????? starting_magnetization(3) = 0.5???
/
&ELECTRONS
??? startingwfc = 'atomic'
??? mixing_mode = 'plain'
??? mixing_beta = 0.6
??? conv_thr = 1.0e-6
??? electron_maxstep= 150
/
&IONS
??? upscale = 15
/
&CELL
?? cell_dynamics = 'bfgs' ,
?? press = 0.00 ,
?? wmass =? 0.00150000? ,
/
ATOMIC_SPECIES
?C? 12.011? C.pz-rrkjus.UPF
?O? 15.9994 O.pz-rrkjus.UPF
ATOMIC_POSITIONS {angstrom}
C??????? 4.132585975?? 4.832995059?? 0.302530806
C??????? 5.456020552?? 5.597038625?? 0.302477533
O??????? 4.794489489?? 5.215547072?? 1.572012872
C??????? 1.698357183?? 4.846620591?? 0.084098745
C??????? 2.888975237?? 5.584067069?? 0.084077187
C??????? 2.927154758?? 2.718125473?? 0.084310286
C??????? 4.161227149?? 3.380362792?? 0.084418771
C??????? 0.411042607?? 2.684363968?? 0.116522861
C??????? 1.676147051?? 3.414879352?? 0.116550940
K_POINTS {automatic}
9 9 1 0 0 0
Model 2: C8O2?
&CONTROL
????? calculation = 'nscf',
????? prefix='C8O2_LDA',
????? restart_mode = 'restart',
????? pseudo_dir ='./',
????? outdir='./'
????? tstress = .true. ,
????? tprnfor = .true. ,
????? nstep =? 100? ,
????? etot_conv_thr = 1.0E-4 ,
????? forc_conv_thr = 1.0D-3 ,
????? dt = 20 ,
/
&SYSTEM
????? ibrav= 4,? celldm(1) = 9.4518, celldm(3)=2, nat = 10, ntyp = 2, nspin=2,
????? ecutwfc =35, ecutrho = 210, occupations='tetrahedra',
????? starting_magnetization(1) = 0.0,
????? starting_magnetization(2) = 0.3,
????? starting_magnetization(3) = 0.5???
/
&ELECTRONS
??? startingwfc = 'atomic'
??? mixing_mode = 'plain'
??? mixing_beta = 0.6
??? conv_thr = 1.0e-6
??? electron_maxstep= 150
/
&IONS
??? upscale = 15
/
&CELL
?? cell_dynamics = 'bfgs' ,
?? press = 0.00 ,
?? wmass =? 0.00150000? ,
/
ATOMIC_SPECIES
?C? 12.011? C.pz-rrkjus.UPF
?O? 15.9994 O.pz-rrkjus.UPF
ATOMIC_POSITIONS {angstrom}
C??????? 0.896514978?? 5.847447161?? 0.369684249
C??????? 2.166323242?? 5.100308876?? 0.369426937
C??????? 3.396879855?? 5.847835514?? 0.029522644
C??????? 4.666783051?? 5.100388577?? 0.029864650
C??????? 2.169717969?? 3.638682147?? 0.193058463
C??????? 3.393684393?? 2.977581062?? 0.193531103
C??????? 4.670322202?? 3.639102512?? 0.208350961
C??????? 5.894369614?? 2.977777255?? 0.207910567
O??????? 1.532383787?? 5.473020020?? 1.633770223
O??????? 4.031020909?? 5.472856877? -1.234119799
K_POINTS {automatic}
9 9 1 0 0 0
-----------------------------------------------
Loc Duong Dinh
Ms-Ph.D Student
Sungkyunkwan Advanced Institute of Nanotechnology,
Sungkyunkwan University,
Suwon, 440-746, Korea
Email: mambom1902 at yahoo.com
