[Pw_forum] large error in RuO2 lattice parameter

[Duy Le]

On Thu, Aug 4, 2011 at 12:36 AM, mohnish pandey <mohnish.iitk at gmail.com> wrote:
> Dear QE users,
> 2.7438
> I want to study RuO2 surfaces. I did calculation of ruthenium metal and
> found the lattice constant right(experimental = 2.70 and 1.584, I got 2.7438
> and 1.582) But after doing calculation of bulk ruthenium oxide I am getting
> very different lattice parameter as compared to the experimental value.
> Experimental value is 4.494 and 3.107 and I am getting the value of 4.6421
> and 3.1888.
> Can anybody please tell from where the discrepancy is coming?
It comes from the difference between theory and experiment.
If you check literature of similar calculation (S. Hong et al, surf.
sci. 2010), you will see that your numbers are really good.

--------------------------------------------------
Duy Le
PhD Candidate
Department of Physics
University of Central Florida.

"Men don't need hand to do things"
> Thanks a lot in advance
>
> input file
>
> &control
>     calculation = 'vc-relax',
>     restart_mode='restart',
>     nstep=100
>     outdir='/home/mohnish/Desktop/Ruo2-bulk',
>     pseudo_dir='/home/mohnish/Desktop/Ruo2-bulk',
>     prefix='Ruo2',
>     tstress = .true.,
>     tprnfor = .true.,
>   /
>   &system
>     ibrav=  6, a = 4.6379, c = 3.1844,nat=  6, ntyp= 2,
>     ecutwfc =
> 40,ecutrho=400,occupations='smearing',degauss=0.01,smearing='gaussian'
>   /
>   &electrons
>    diagonalization='david'
>    mixing_mode = 'plain'
>    mixing_beta = 0.7
>    conv_thr = 1.0d-8
>    startingpot = 'file'
>    startingwfc = 'file'
>  /
> &IONS
>  ion_dynamics='bfgs'
> /
> &CELL
>  cell_dynamics = 'bfgs'
> /
> ATOMIC_SPECIES
>   Ru 101.07 Ru.pbe-n-van.UPF
>   O  15.099 O.pbe-rrkjus.UPF
>  ATOMIC_POSITIONS (crystal)
> Ru  0.00000000  0.00000000  0.00000000
> Ru  0.50000000  0.50000000  0.50000000
> O   0.30600000  0.30600000  0.00000000
> O   0.69400000  0.69400000  0.00000000
> O   0.19400000  0.80600000  0.50000000
> O   0.80600000  0.19400000  0.50000000
>  K_POINTS (automatic)
>  10 10 12 0 0 0
>
>
> Section of output file,
>
> bfgs converged in   8 scf cycles and   4 bfgs steps
>      (criteria: energy < 0.10E-03, force < 0.10E-02, cell < 0.50E+00)
>
>      End of BFGS Geometry Optimization
>
>      Final enthalpy =    -227.8256404205 Ry
> Begin final coordinates
>      new unit-cell volume =    463.72196 a.u.^3 (    68.71650 Ang^3 )
>
> CELL_PARAMETERS (alat=  8.76436083)
>    1.000910330   0.000000000   0.000000000
>    0.000000000   1.000910330   0.000000000
>    0.000000000   0.000000000   0.687553615
>
> ATOMIC_POSITIONS (crystal)
> Ru       0.000000000   0.000000000   0.000000000
> Ru       0.500000000   0.500000000   0.500000000
> O        0.306258404   0.306258404   0.000000000
> O        0.693741596   0.693741596   0.000000000
> O        0.193741596   0.806258404   0.500000000
> O        0.806258404   0.193741596   0.500000000
> End final coordinates
>
> --
> Regards,
> MOHNISH,
> -----------------------------------------------------------------
> Mohnish Pandey
> Senior Project Associate,
> Department of Chemical Engineering,
> IIT KANPUR, UP, INDIA
> -----------------------------------------------------------------
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
>