Hi, Vega: A recent result (Jpn. J. Appl. Phys. 39 (2000) L847) showed that different pseudopotential leaded to different conclusions.
Best, Wei On Thu, Aug 28, 2008 at 4:28 AM, vega <vegalew at hotmail.com> wrote: > Dear all, > > It is known that the rutile is more stable than anatase in thermodynamics. > Surprisingly, when I did the vc-relax calculation by QE, I found > the calculated energy of anatase lower than rutile. Both vc-relax > calculation for rutile and anatase onverged in 6 scf cycles and 3 bfgs > steps, giving the final enthalpy = -362.7585836890 Ry for rutile and > -725.5447425835 Ry for antase. So the average energy of [TiO2] unit > is -181.3792918445 Ry for rutile and -181.386185645875 Ry for anatase. It > looks like anatase is more stable than rutile. Do you think it was quite > strange? > > To make the calculation both for anatase and rutile comparable, I used the > same ecutwfc=40 Ry and ecutwfc=400 Ry, and a quite dense k-point mesh for > both case, 4x4x7 for rutile and 5x5x2 for anatase. > > for better understanding in my calculation, please read the input file > below, > for anatase case, > &CONTROL > title = 'Anatase lattice' , > calculation = 'vc-relax' , > restart_mode = 'from_scratch' , > outdir = > '/home/hjfeng/vega/TiO2/Anatase/lattice/vctest/tmp/' , > wfcdir = '/tmp/' , > pseudo_dir = '/home/hjfeng/vega/espresso-4.0/pseudo/' , > prefix = 'Anatase lattice' , > disk_io = 'none' , > nstep = 1000 , > / > &SYSTEM > ibrav = 6, > celldm(1) = 7.1356, > celldm(3) = 2.5122, > nat = 12, > ntyp = 2, > ecutwfc = 40 , > ecutrho = 400 , > / > &ELECTRONS > > / > &IONS > ion_dynamics = 'bfgs' , > / > &CELL > cell_dynamics = 'bfgs' , > / > ATOMIC_SPECIES > Ti 47.86700 Ti.pw91-sp-van_ak.UPF > O 15.99940 O.pw91-van_ak.UPF > ATOMIC_POSITIONS crystal > Ti 0.000000000 0.000000000 0.000000000 > Ti 0.500000000 0.500000000 0.500000000 > Ti 0.000000000 0.500000000 0.250000000 > Ti 0.500000000 0.000000000 0.750000000 > O 0.000000000 0.500000000 0.042000000 > O 0.000000000 0.000000000 0.208000000 > O 0.500000000 0.500000000 0.292000000 > O 0.000000000 0.500000000 0.458000000 > O 0.500000000 0.000000000 0.542000000 > O 0.500000000 0.500000000 0.708000000 > O 0.000000000 0.000000000 0.792000000 > O 0.500000000 1.000000000 0.958000000 > K_POINTS automatic > 5 5 2 1 1 1 > > for rutile case, > > &CONTROL > title = Rutile_lattice , > calculation = 'vc-relax' , > restart_mode = 'from_scratch' , > outdir = > '/home/vega32/TiO2/rutile/lattice/vcrelax/tmp' , > wfcdir = '/tmp/' , > pseudo_dir = '/home/vega32/espresso-4.0.1/pseudo/' , > prefix = 'Anatase lattice' , > disk_io = 'none' , > nstep = 1000 , > / > &SYSTEM > ibrav = 6, > celldm(1) = 8.6814, > celldm(3) = 0.6441, > nat = 6, > ntyp = 2, > ecutwfc = 40 , > ecutrho = 400 , > / > &ELECTRONS > > / > &IONS > ion_dynamics = 'bfgs' , > / > &CELL > cell_dynamics = 'bfgs' , > / > ATOMIC_SPECIES > O 15.99940 O.pw91-van_ak.UPF > Ti 47.90000 Ti.pw91-sp-van_ak.UPF > ATOMIC_POSITIONS crystal > O 0.304800000 0.304800000 0.000000000 > O 0.695200000 0.695200000 0.000000000 > O 0.195200000 0.804800000 0.500000000 > O 0.804800000 0.195200000 0.500000000 > Ti 0.500000000 0.500000000 0.500000000 > Ti 0.000000000 0.000000000 0.000000000 > K_POINTS automatic > 4 4 7 1 1 1 > > vega > > ============================================================== > Vega Lew ( weijia liu) > PH.D Candidate in Chemical Engineering > State Key Laboratory of Materials-oriented Chemical Engineering > College of Chemistry and Chemical Engineering > Nanjing University of Technology, 210009, Nanjing, Jiangsu, China > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20080829/5a31d55d/attachment.htm
