Dear QE users,<br>2.7438 <br>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?<br>
<br>Thanks a lot in advance<br><br><b>input file</b><br><br>&control<br> calculation = 'vc-relax',<br> restart_mode='restart',<br> nstep=100<br> outdir='/home/mohnish/Desktop/Ruo2-bulk',<br>
pseudo_dir='/home/mohnish/Desktop/Ruo2-bulk',<br> prefix='Ruo2',<br> tstress = .true.,<br> tprnfor = .true.,<br> /<br> &system <br> ibrav= 6, a = 4.6379, c = 3.1844,nat= 6, ntyp= 2,<br>
ecutwfc = 40,ecutrho=400,occupations='smearing',degauss=0.01,smearing='gaussian'<br> /<br> &electrons<br> diagonalization='david'<br> mixing_mode = 'plain'<br> mixing_beta = 0.7<br>
conv_thr = 1.0d-8<br> startingpot = 'file'<br> startingwfc = 'file'<br> /<br>&IONS<br> ion_dynamics='bfgs'<br>/<br>&CELL<br> cell_dynamics = 'bfgs'<br>/<br>ATOMIC_SPECIES<br>
Ru 101.07 Ru.pbe-n-van.UPF<br> O 15.099 O.pbe-rrkjus.UPF<br> ATOMIC_POSITIONS (crystal)<br>Ru 0.00000000 0.00000000 0.00000000<br>Ru 0.50000000 0.50000000 0.50000000<br>O 0.30600000 0.30600000 0.00000000<br>
O 0.69400000 0.69400000 0.00000000<br>O 0.19400000 0.80600000 0.50000000<br>O 0.80600000 0.19400000 0.50000000<br> K_POINTS (automatic)<br> 10 10 12 0 0 0<br clear="all"><br><br><b>Section of output file,</b><br>
<br>bfgs converged in 8 scf cycles and 4 bfgs steps<br> (criteria: energy < 0.10E-03, force < 0.10E-02, cell < 0.50E+00)<br><br> End of BFGS Geometry Optimization<br><br> Final enthalpy = -227.8256404205 Ry<br>
Begin final coordinates<br> new unit-cell volume = 463.72196 a.u.^3 ( 68.71650 Ang^3 )<br><br>CELL_PARAMETERS (alat= 8.76436083)<br> 1.000910330 0.000000000 0.000000000<br> 0.000000000 1.000910330 0.000000000<br>
0.000000000 0.000000000 0.687553615<br><br>ATOMIC_POSITIONS (crystal)<br>Ru 0.000000000 0.000000000 0.000000000<br>Ru 0.500000000 0.500000000 0.500000000<br>O 0.306258404 0.306258404 0.000000000<br>
O 0.693741596 0.693741596 0.000000000<br>O 0.193741596 0.806258404 0.500000000<br>O 0.806258404 0.193741596 0.500000000<br>End final coordinates<br><br>-- <br>Regards,<br>MOHNISH,<br>-----------------------------------------------------------------<br>
Mohnish Pandey<br>Senior Project Associate,<br>Department of Chemical Engineering,<br>IIT KANPUR, UP, INDIA<br>-----------------------------------------------------------------<br>