El 06-08-2019 09:28, MARIA CATERINA CEVALLOS BRENES escribió:
> Dear QE community:
>
> I am having several errors when trying to get the relaxed structure of
> polyacetylene. I am supposed to get 1.36 and 1.43 as the dimer bond lengths
> (for C=C and C-C respectively).
>
> I am using vc-relax method, just allowing z lattice parameter (along the
> chain) to change.
>
> Here is my input file:
>
> &control
>
> calculation = 'vc-relax',
>
> prefix = 'pa',
>
> verbosity = 'low',
>
> pseudo_dir = '/home/ccevallos/pslibrary.1.0.0/pbe/PSEUDOPOTENTIALS',
>
> outdir = './tmp',
>
> wf_collect=.true.
>
> /
>
> &SYSTEM
>
> ibrav = 0,
>
> nat=4,
>
> ntyp=2,
>
> ecutwfc=200.00,
>
> occupations = 'fixed',
>
> input_DFT='PBE',
>
> nbnd= 12,
>
> /
>
> &ELECTRONS
>
> /
>
> &ions
>
> /
>
> &cell
>
> cell_dofree='z'
>
> /
>
> ATOMIC_SPECIES
>
> C 12.011 C.pbe-n-rrkjus_psl.1.0.0.UPF
>
> H 1.00784 H.pbe-rrkjus_psl.1.0.0.UPF
>
> CELL_PARAMETERS {angstrom}
>
> 5.000000000000000 0.000000000000000 0.000000000000000
>
> 0.000000000000000 5.000000000000000 0.000000000000000
>
> 0.000000000000000 0.000000000000000 2.4
>
> ATOMIC_POSITIONS {angstrom}
>
> C 2.8 0 0
>
> C 2.1 0 1.16
>
> H 3.89 0 0
>
> H 3.19 0 1.16
>
> K_POINTS automatic
>
> 2 2 25 1 1 1
>
> However I am getting the following error:
>
> Error in routine cdiaghg (30):
>
> S matrix not positive definite
>
> What am I doing wrong? I also tried using a larger supercell, with 4 Carbon
> atoms, and it gives the same error, but you can see the bond length getting
> closer to 1.39 for al C-C bond lengths. In the latter case, why am I not
> observing the Peierls distortion?
>
> Thank you very much in advance!
>
> Best regards,
>
> Caterina Cevallos.
>
> QCLab. University of Costa Rica
>
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso [1])
> users mailing list [email protected]
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There are two errors with the input file:
Last atomic position should be:
H 1.01 0 1.16
and nbnd=10
However, I'm still not getting the dimerization expected.
Links:
------
[1] http://www.max-centre.eu/quantum-espresso
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