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<DIV><FONT face=Arial size=2>Thanks for the help from Nicola and
Charles.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>vega</FONT></DIV>
<DIV style="FONT: 10pt Tahoma">
<DIV><FONT face=Arial></FONT><FONT face=Arial></FONT><BR></DIV>
<DIV style="BACKGROUND: #f5f5f5">
<DIV style="font-color: black"><B>From:</B> <A title=vegalew@hotmail.com
href="mailto:vegalew@hotmail.com">vega</A> </DIV>
<DIV><B>Sent:</B> Thursday, August 28, 2008 4:28 PM</DIV>
<DIV><B>To:</B> <A title=pw_forum@pwscf.org
href="mailto:pw_forum@pwscf.org">PWSCF</A> </DIV>
<DIV><B>Subject:</B> [Pw_forum] something strange in rutile and anatase
calculation</DIV></DIV></DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>Dear all,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>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?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>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.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>for better understanding in my calculation, please
read the input file below,</FONT></DIV>
<DIV><FONT face=Arial size=2>for anatase case,</FONT></DIV>
<DIV><FONT face=Arial
size=2>&CONTROL<BR>
title = 'Anatase lattice'
,<BR>
calculation = 'vc-relax'
,<BR>
restart_mode = 'from_scratch'
,<BR>
outdir = '/home/hjfeng/vega/TiO2/Anatase/lattice/vctest/tmp/'
,<BR>
wfcdir = '/tmp/'
,<BR>
pseudo_dir = '/home/hjfeng/vega/espresso-4.0/pseudo/'
,<BR>
prefix = 'Anatase lattice'
,<BR>
disk_io = 'none'
,<BR>
nstep = 1000
,<BR> /<BR> &SYSTEM<BR>
ibrav =
6,<BR>
celldm(1) =
7.1356,<BR>
celldm(3) =
2.5122,<BR>
nat =
12,<BR>
ntyp =
2,<BR>
ecutwfc = 40
,<BR>
ecutrho = 400 ,<BR> /<BR> &ELECTRONS</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial
size=2> /<BR> &IONS<BR>
ion_dynamics = 'bfgs'
,<BR> /<BR> &CELL<BR>
cell_dynamics = 'bfgs' ,<BR> /<BR>ATOMIC_SPECIES<BR>
Ti 47.86700 Ti.pw91-sp-van_ak.UPF <BR>
O 15.99940 O.pw91-van_ak.UPF <BR>ATOMIC_POSITIONS crystal
<BR> Ti 0.000000000
0.000000000 0.000000000 <BR>
Ti 0.500000000
0.500000000 0.500000000 <BR>
Ti 0.000000000
0.500000000 0.250000000 <BR>
Ti 0.500000000
0.000000000 0.750000000
<BR> O
0.000000000 0.500000000
0.042000000 <BR>
O 0.000000000
0.000000000 0.208000000
<BR> O
0.500000000 0.500000000
0.292000000 <BR>
O 0.000000000
0.500000000 0.458000000
<BR> O
0.500000000 0.000000000
0.542000000 <BR>
O 0.500000000
0.500000000 0.708000000
<BR> O
0.000000000 0.000000000
0.792000000 <BR>
O 0.500000000
1.000000000 0.958000000 <BR>K_POINTS
automatic <BR> 5 5 2 1 1 1 </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>for rutile case,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV> &CONTROL<BR>
title = Rutile_lattice
,<BR>
calculation = 'vc-relax'
,<BR>
restart_mode = 'from_scratch'
,<BR>
outdir = '/home/vega32/TiO2/rutile/lattice/vcrelax/tmp'
,<BR>
wfcdir = '/tmp/'
,<BR>
pseudo_dir = '/home/vega32/espresso-4.0.1/pseudo/'
,<BR>
prefix = 'Anatase lattice'
,<BR>
disk_io = 'none'
,<BR>
nstep = 1000
,<BR> /<BR> &SYSTEM<BR>
ibrav =
6,<BR>
celldm(1) =
8.6814,<BR>
celldm(3) =
0.6441,<BR>
nat =
6,<BR>
ntyp =
2,<BR>
ecutwfc = 40
,<BR>
ecutrho = 400 ,<BR> /<BR> &ELECTRONS</DIV>
<DIV> </DIV>
<DIV> /<BR> &IONS<BR>
ion_dynamics = 'bfgs'
,<BR> /<BR> &CELL<BR>
cell_dynamics = 'bfgs' ,<BR> /<BR>ATOMIC_SPECIES<BR>
O 15.99940 O.pw91-van_ak.UPF<BR> Ti
47.90000 Ti.pw91-sp-van_ak.UPF<BR>ATOMIC_POSITIONS
crystal <BR> O
0.304800000 0.304800000
0.000000000 <BR>
O 0.695200000
0.695200000 0.000000000
<BR> O
0.195200000 0.804800000
0.500000000 <BR>
O 0.804800000
0.195200000 0.500000000 <BR>
Ti 0.500000000
0.500000000 0.500000000 <BR>
Ti 0.000000000
0.000000000 0.000000000 <BR>K_POINTS
automatic <BR> 4 4 7 1 1 1 </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>vega</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial
size=2>==============================================================<BR>Vega
Lew ( weijia liu)<BR>PH.D Candidate in Chemical Engineering<BR>State Key
Laboratory of Materials-oriented Chemical Engineering<BR>College of Chemistry
and Chemical Engineering<BR>Nanjing University of Technology, 210009, Nanjing,
Jiangsu, China</FONT></DIV>
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