Dear all,
Thank to all your help, I could run a Q-E calculation on my cluster more
correctly. Now I can learn to do some
simple calculations.
My first job is to calculate the Anatase-TiO2 lattice cell parameter using Q-E
and compare it with literature.
I have tested the BFGS for vc-relax, but the cell parameters changed so much
that an error was occured with
the information 'non orthogonal operation'. Then I used a symmetry-conserving
algorithm as the QE manual
said. The input file as following,
&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 = 0.000000735 ,
forc_conv_thr = 0.0011668141375 ,
nstep = 1000 ,
/
&SYSTEM
ibrav = 6,
celldm(1) = 7.135605333,
celldm(3) = 2.5121822033898305084745762711864,
nat = 12,
ntyp = 2,
ecutwfc = 25 ,
ecutrho = 200 ,
/
&ELECTRONS
conv_thr = 7.3D-8 ,
/
&IONS
ion_dynamics = 'damp' ,
/
&CELL
cell_dynamics = 'damp-w' ,
/
ATOMIC_SPECIES
Ti 47.86700 Ti.pw91-sp-van_ak.UPF
O 15.99940 O.pw91-van_ak.UPF
ATOMIC_POSITIONS angstrom
Ti 0.000000000 0.000000000 0.000000000
Ti 1.888000000 1.888000000 4.743000000
Ti 0.000000000 1.888000000 2.372000000
Ti 1.888000000 0.000000000 7.115000000
O 0.000000000 0.000000000 1.973000000
O 1.888000000 1.888000000 6.716000000
O 0.000000000 1.888000000 4.345000000
O 1.888000000 0.000000000 9.088000000
O 1.888000000 0.000000000 5.141000000
O 0.000000000 1.888000000 0.398000000
O 1.888000000 1.888000000 2.770000000
O 0.000000000 0.000000000 7.513000000
K_POINTS automatic
7 7 3 1 1 1
The calculation can be done nearly 600 fs. The last few lines of results file
is shown at the bottom.
But the cell parameters for Anatase lattice seems to be not perfectly match the
results in literature.
In the literature, Journal of Physical Chemistry B, 2006, 110, 7464, the author
used a conjugate-gradient
or quasi-Newton scheme as implemented in VASP to optimaize the geometries. And
the cell parameters
are a = b = 3.803 A c = 9.603 A c/a = 2.525. But my Q-E result, a= 3.7546166A
b= 3.75461729A c= 9.3911A
seems to be much smaller than his. I tried times times again, even, the
starting geometry is from the
exprimental data for Journal of the American Society, 1987,109, 3639, which
was also cited by him, the
result was still that small.
I also have tested it in CASTEP, using BFGS and same precision. The CASTEP
results were a = b =3.798668A
c = 9.693431A c/a = 2.5518, which seemed to be more close to the literature
results. The starting geometry
was also from Journal of the American Society, 1987,109, 3639.
I think maybe some parameter in my Q-E input file was wrong. Could you please
point it to me?
thank you for reading. I am waiting for your responding.
Vega Lew
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
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