[Pw_forum] CaCuO2 and LDA+U

[Axel Kohlmeyer]

On Mon, 24 Mar 2008, Chao Cao wrote:

CC> So, no one has any idea?

i'd expect that most people, who would feel qualified
to answer, are currently in easter holidays.

there are countries where those are taken much more
seriously than the US (and include easter monday)...

axel.

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

-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
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