If you set occupancies to "fixed", the code assumes that the system is
an insulator and computes the HOMO as the highest N-th Kohn-Sham state,
the LUMO as the lowest (N+1)-th KS state (N=half the number of
electrons). If the system does not want to be an insulator, the "HOMO"
might turn out to have higher energy than the "LUMO".
Paolo
On 09/03/2024 03:38, wangzongyi via users wrote:
Dear all
I am trying to calculate metallic oxide(CoO). However, I have some
puzzle in writing vcrelax.in file.
As the experience shows that CoO is insulator, my vcrelax.in file is
showed in the following lines, I calculate it as insulator
* &control*
* calculation='vc-relax'*
* restart_mode='from_scratch',*
* prefix='CoO'*
* pseudo_dir = '../../files/pseudo'*
* outdir='./tmp'*
* verbosity='high'*
* etot_conv_thr = 1.0D-4*
* forc_conv_thr = 1.0D-3*
* /*
* &system*
* ibrav = 0,*
* celldm(1) = 8.00,*
* nat = 4,*
* ntyp = 3,*
* ecutwfc = 50.0*
* ecutrho = 400.0*
* nspin = 2*
* tot_magnetization=0.00*
* occupations = 'fixed',*
* nbnd = 28*
* /*
* &electrons*
* conv_thr = 1.d-10*
* startingwfc ='file'*
* startingpot ='file'*
* /*
* &ions*
* ion_dynamics = 'bfgs'*
* /*
* &cell*
* cell_dynamics = 'bfgs'*
* /*
*ATOMIC_SPECIES*
* Co1 58.933194 co_pbesol_v1.2.uspp.F.UPF*
* Co2 58.933194 co_pbesol_v1.2.uspp.F.UPF*
* O 15.999 O.pbesol-n-kjpaw_psl.0.1.UPF*
*ATOMIC_POSITIONS {crystal}*
*Co1 0.00000000 0.00000000 0.00000000*
*Co2 0.50000000 0.50000000 0.50000000*
*O 0.25000000 0.25000000 0.25000000*
*O 0.75000000 0.75000000 0.75000000*
*CELL_PARAMETERS {alat}*
* 0.570726115 0.570726115 1.031099100*
* 0.570726115 1.031099100 0.570726115*
* 1.031099100 0.570726115 0.570726115*
*K_POINTS {automatic}*
* 6 6 6 0 0 0*
*HUBBARD {ortho-atomic}*
*U Co1-3d 6.7553*
*U Co2-3d 6.7553*
however, the outfile shows that
*highest occupied, lowest unoccupied level (ev): 14.3247 13.7975*
I am puzzled, what happened, why is homo higher than lumo? is my
calculation correect? Or should I regard the system as matel when
calculate varelax?
Thank you very much
--
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine Italy, +39-0432-558216
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