[Pw_forum] CaCuO2 and LDA+U

[Chao Cao]

So, no one has any idea?


Chao Cao wrote:
> Dear PWSCF users and developers:
>
> I have been trying to use PWSCF's implementation of LDA+U to calculate 
> the electronic structure of CaCuO2 lately. In VASP, once I turn on U, it 
> gives AFM ground state and reasonable gap separation at E_F. However, 
> the procedure seems to be much harder for PWSCF. While it gets AFM gs 
> correctly, I can never get a band gap. I searched the forum, and I 
> realized that the initial occupation number might be important, but the 
> several combinations I tried seem to give me the same result. So, is 
> there any hint or suggestions, especially how to choose initial 
> occupation numbers? Thanks in advance.
>
>
> Best,
>
> Chao Cao
>
>
> And, here's my input file:
>
> &control
>   calculation = 'scf'
>   restart_mode = 'from_scratch'
>   prefix = 'CaCuO2'
>   disk_io = 'low'
>   outdir = './'
> /
> &system
>   ibrav = 0, celldm(1) = 1.88972688, ntyp = 4, nat = 16
>   nbnd=80, ecutwfc = 32, ecutrho = 400
>   nspin = 2, starting_magnetization(2)=0.5, starting_magnetization(3)=-0.5
>   lda_plus_u = .true., Hubbard_U(2) = 6.5, Hubbard_U(3) = 6.5
>   occupations = 'smearing', smearing = 'mp', degauss = 0.007
> /
> &electrons
>   mixing_beta = 0.2
>   conv_thr = 1.0d-9
> /
> ATOMIC_SPECIES
> Ca   1.0  Ca.pbe-nsp-van.UPF
> Cuu  1.0  Cu.pbe-n-van.UPF
> Cud  1.0  Cu.pbe-n-van.UPF
> O    1.0   O.pbe-van.UPF
> ATOMIC_POSITIONS crystal
> Ca   0.25  0.75  0.25
> Ca   0.75  0.25  0.25
> Ca   0.25  0.75  0.75
> Ca   0.75  0.25  0.75
> Cuu  0.25  0.25  0.00
> Cuu  0.75  0.75  0.50
> Cud  0.75  0.75  0.00
> Cud  0.25  0.25  0.50
> O    0.00  0.00  0.00
> O    0.50  0.00  0.00
> O    0.00  0.50  0.00
> O    0.50  0.50  0.00
> O    0.00  0.00  0.50
> O    0.50  0.00  0.50
> O    0.00  0.50  0.50
> O    0.50  0.50  0.50
> K_POINTS automatic
>   8,8,4,1,1,1
> CELL_PARAMETERS cubic
>    3.878393250   3.878393249   0.000000000
>   -3.878393249   3.878393250   0.000000000
>    0.000000000   0.000000000   6.409031058
>
>
>
>
>   


-- 
Chao Cao

Quantum Theory Project and Department of Physics
University of Florida, Gainesville, FL 32611
U.S.A.