[Pw_forum] dexx negative with gaupbe

[Aswathi Mohan]

Hi QE Users,
I was running hybrid calculations for the system mentioned below, using QE
6.0. I did calculations with gaupbe and as soon as the value of dexx came
down to 8th decimal place, it ended up with the error ''dexx is negative!
Check that exxdiv_treatment is appropriate for the system". Is there any
way to fix this??


Input file :

    &control
    calculation = 'scf'
    restart_mode='from_scratch',
    prefix='titanium',
    pseudo_dir = '/home/aswathi/pseudo',
    outdir='./tmp'
 /
 &system
    ibrav=4, celldm(1) =5.787830241, celldm(3) =5.87699818, nat=  3, ntyp=
3, nspin= 2,
    ecutwfc =55, ecutrho =480, occupations=
'smearing',starting_magnetization(1)= 1.0, starting_magnetization(2)= -1.0,
smearing= 'mv',
    degauss= 0.007,exxdiv_treatment='none', input_dft='gaupbe',
nqx1=1,nqx2=1,nqx3=1,x_gamma_extrapolation=.false.
 /
 &electrons
    electron_maxstep = 150
    diagonalization='david'
    mixing_mode = 'local-TF'
    mixing_beta = 0.2
    conv_thr =  1.0d-8

 /
 &ions
 /
ATOMIC_SPECIES
 Ti1 47.867 Ti.pbe-spn-rrkjus_psl.1.0.0.UPF
 Ti2 47.867 Ti.pbe-spn-rrkjus_psl.1.0.0.UPF
  C  12.01  C.pbe-rrkjus.UPF
ATOMIC_POSITIONS {angstrom}
Ti1      1.531455936   0.881865175   7.959046872
Ti2     -0.002007986   1.767215320   5.683028107
C       -0.000448669  -0.000776058   6.820915393

K_POINTS {automatic}
11 11 1 0 0 0

Regards,
Aswathi Mohan T
Ph. D.
IISER PUNE
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