[Pw_forum] something strange in rutile and anatase calculation

[vega]

>A recent result (Jpn. J. Appl. Phys. 39 (2000) L847) showed that different pseudopotential leaded to different conclusions. 
thank you for your information.
I have no subscription for this japanese journal. Please sent it to vegalew at gmail.com if you like me to read it.
I am rather curious to know about it.

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


From: willy kohn 
Sent: Saturday, August 30, 2008 2:02 AM
To: PWSCF Forum 
Subject: Re: [Pw_forum] something strange in rutile and anatase calculation


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






--------------------------------------------------------------------------------


_______________________________________________
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://lists.quantum-espresso.org/pipermail/users/attachments/20080830/69f0da72/attachment.html>