[Pw_forum] Anatase lattice parameters testing results

[vega lew]

Dear all,
There is someting wrong with last mail, so I send it again.
Now I have tested Anatase lattice parameters using new BFGS file of PWscf. The new BFGS filesseem to be perfect. The data in following table is calculated by PWscf except for the first two lines.The first line is the experimental data at 15K of J. Am. Chem. SOC. 1987, 109, 3639-3646.The second line is the average value calculated by CASTEP. But the value is not stable, it'swould be changed a bit of different run.From the third line to the bottom is the data calculated by PWscf. The value is quite stable.The value remain the same when calculate by same number of CPUs and pools. There would be  only a little different for different number of CPUs and pools, less than 0.01% in energy. 
K-point  mesh      Pseudopotentials  Cutoff  / Ry       Anatase  lattice parameters                    time        
                                                                      a=b              c         Energy  / Ry         CPU      Wall        
experiment*                        x                           3.78216      9.50465            x                     x         x     
CASTEP                        400 eV                         3.7987       9.6934       -730.11745                     
gamma  (1X1X1)            30,240                         3.39021      11.77804    -725.08174      4m18.70s      18m 9.12s        
2X2X1                          30，240                       3.8683         9.0275      -725.48834      8m 4.25s       32m33.56s   
4X4X2                          25,200                         3.7500        9.3829      -725.41398      9m58.82s      17m46.87s
                                   30,240                         3.7899       9.6203       -725.49520      3m41.55s      7m50.32s   
                                   40,320                         3.7850       9.5716       -725.54336      8m54.73s      34m  1.43s     
                                   50,400                         3.7926      9.6366       -725.59434       10m14.46s      41m  3.22s    
7X7X3                           30,240                         3.7919      9.6058        -725.49443      31m59.60s      46m37.77s        
10X10X4                       30,240                          3.7916      9.6067        -725.49451      31m32.94s      44m  4.11s   
The input file as follows,  &CONTROL                       title = 'Anatase lattice' ,                 calculation = 'vc-relax' ,                restart_mode = 'from_scratch' ,                      outdir = '/home/vega/espresso-4.0/tmp/' ,                      wfcdir = '/tmp/' ,                  pseudo_dir = '/home/vega/espresso-4.0/pseudo/' ,                      prefix = 'Anatase lattice default' ,                     disk_io = 'none' ,               etot_conv_thr = 0.0005 ,               forc_conv_thr = 0.0011668141375 ,                       nstep = 1000 , / &SYSTEM                       ibrav = 6,                   celldm(1) = 7.1356,                   celldm(3) = 2.5122,                         nat = 12,                        ntyp = 2,                     ecutwfc = 30 ,                     ecutrho = 240 , / &ELECTRONS                    conv_thr = 7.3D-8 , / &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.UPFATOMIC_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    0.958000000K_POINTS automatic2 2 1  1 1 1 But it is especially strange that the total energy was -730.11745 Ry, rather different than the PWscf's results. Also PWscf's results seems to be a litter lager than experimental data. Is it because the pseudopotential Ti.pw91-sp-van_ak.UPF underbinding for TiO2?  Vega LewPH.D Candidate in Chemical EngineeringState Key Laboratory of Materials-oriented Chemical EngineeringCollege of Chemistry and Chemical EngineeringNanjing University of Technology, 210009, Nanjing, Jiangsu, ChinaVega LewPH.D Candidate in Chemical EngineeringState Key Laboratory of Materials-oriented Chemical EngineeringCollege of Chemistry and Chemical EngineeringNanjing University of Technology, 210009, Nanjing, Jiangsu, China
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