[Pw_forum] R: Re: WZ and ZB ZnO
giacsport at libero.it
giacsport at libero.it
Wed Feb 29 07:56:40 CET 2012
Dear Monish, thanks a lot for the prompt and exhaustive reply. I was wondering that I took an experimental geometry for both WZ and ZB, thus I was thinking that performing a simple "scf" calculation should have reproduce the experimental trend.
Thanks a lot!With best regards,Giacomo
----Messaggio originale----
Da: mohnish.iitk at gmail.com
Data: 29/02/2012 4.37
A: "giacsport at libero.it"<giacsport at libero.it>
Ogg: Re: [Pw_forum] WZ and ZB ZnO
Dear Giacomo,
Are you sure that you optimized the structure with "calculation" = "vc-relax" flag? I mean after the optimization the forces and stress should be below the threshold value. And I use PBE ultrasoft pseudopotential and it worked pretty well for me. Below are the inputs attached : By the way the "nspin" flag that you are using needs finite starting magnetization for atleast one species otherwise it wont do the spin polarized calculation. Feel free to ask any further doubt you have.
Wurtzite:
&control
calculation = 'vc-relax',
restart_mode='restart',
nstep=300
outdir='/home/rajpala/Desktop/zno-wur',
pseudo_dir='/home/rajpala/Desktop/zno-wur'
prefix='zno',
tstress = .true.,
tprnfor = .true.,
/
&system
ibrav= 4, a = 3.25, c = 5.25,nat= 4, ntyp= 2,
ecutwfc = 35,ecutrho=280,occupations='smearing',degauss=0.01,smearing='gaussian'
/
&electrons
diagonalization='david'
mixing_mode = 'plain'
mixing_beta = 0.7
conv_thr = 1.0d-8
/
&IONS
ion_dynamics='bfgs'
trust_radius_min=1.D-7
/
&CELL
cell_dynamics='bfgs'
/
ATOMIC_SPECIES
Zn 65.390 Zn.pbe-van.UPF
O 15.099 O.pbe-rrkjus.UPF
ATOMIC_POSITIONS (crystal)
Zn 0.000000000000 0.0000000000 0.00000000000
Zn 0.333333333333 0.6666666667 0.50000000000
O 0.000000000000 0.0000000000 0.34500000000
O 0.333333333333 0.6666666667 0.84500000000
K_POINTS (automatic)
8 8 6 0 0 0
Final enthalpy = -317.1024506964 Ry = -158.551225348 Ry/formula unit.
Zincblende :
&control
calculation = 'vc-relax'
prefix='zno'
tstress = .true.
tprnfor = .true.
outdir="/home/rajpala/Desktop/zno-zincblend-bulk"
pseudo_dir="/home/rajpala/Desktop/zno-zincblend-bulk"
/
&system
ibrav= 2, a =4.60,nat= 2, ntyp= 2,ecutwfc = 40,ecutrho =320, occupations='smearing',degauss=0.01,smearing='gaussian'
/
&electrons
diagonalization='david'
mixing_mode = 'plain'
mixing_beta = 0.7
conv_thr = 1.0d-8
/
&IONS
ion_dynamics='bfgs'
/
&CELL
cell_dynamics='bfgs'
/
ATOMIC_SPECIES
Zn 65.390 Zn.pbe-van.UPF
O 15.099 O.pbe-rrkjus.UPF
ATOMIC_POSITIONS (crystal)
Zn 0.00 0.00 0.00
O 0.25 0.25 0.25
K_POINTS (automatic)
6 6 6 0 0 0
Final enthalpy = -158.5504170143 Ry/formula unit
On Wed, Feb 29, 2012 at 8:31 AM, giacsport at libero.it <giacsport at libero.it> wrote:
Dear all, regardless the pseudopotentials I use for my optimization and the kpoint sampling, I always obtain that ZB phase of ZnO is (slightly) more stable than WZ.
Since I would like to make HSE calculations on such systems I would like to have an already well-ordered (in terms of energy, of course) structures at PBE level. (In my case WZ and ZB look almost degenerate, but always with ZB slightly more stable than WZ)
Can anyone help me to refine parameters that allow me to obtain E WZ < E ZB. Here you find the two inputs.
Wurtzite ZnO&CONTROL
calculation = "scf"
pseudo_dir = './'
outdir='./',
restart_mode="from_scratch",
prefix='ZnO_WZ',
tprnfor = .true.,
tstress = .true.,
wf_collect=.true.,
/
&SYSTEM
ibrav= 4, celldm(1) =6.13821, celldm(3)=1.6023951, nat= 4, ntyp= 2,
ecutwfc =90.0, nbnd = 80, nspin=2, tot_magnetization=0,
/
&ELECTRONS
diagonalization='david'
mixing_mode = 'plain'
mixing_beta = 0.7
conv_thr = 1.0d-8
/
ATOMIC_SPECIES
Zn 65.38 Zn-GGA-pbe.fhi.UPF
O 15.9994 O-GGA-pbe.fhi.UPF
ATOMIC_POSITIONS (crystal)
Zn 0.33333 0.66667 0.00000
Zn 0.66667 0.33333 0.50000
O 0.33333 0.66667 0.38210
O 0.66667 0.33333 0.88210
K_POINTS (automatic)
12 12 9 0 0 0
total energy = -285.55060915 Ry/2 = -142.7753045750
Zincblende ZnO&control
calculation = 'scf'
restart_mode='from_scratch',
prefix='ZnO_ZB',
tprnfor = .true.,
tstress = .true.,
wf_collect=.true.,
pseudo_dir='./',
outdir='./',
/
&system
ibrav= 1, celldm(1) =8.730534067
nat= 8, ntyp= 2,
ecutwfc =90., nbnd = 100, nspin=2, tot_magnetization=0
/
&electrons
diagonalization='david'
mixing_mode = 'plain'
mixing_beta = 0.7
conv_thr = 1.0d-8
/
ATOMIC_SPECIES
Zn 65.38 Zn-GGA-pbe.fhi.UPF
O 15.9994 O-GGA-pbe.fhi.UPF
ATOMIC_POSITIONS (crystal)
Zn 0.00000 0.00000 0.00000
Zn 0.00000 0.50000 0.50000
Zn 0.50000 0.00000 0.50000
Zn 0.50000 0.50000 0.00000
O 0.25000 0.25000 0.25000
O 0.25000 0.75000 0.75000
O 0.75000 0.75000 0.25000
O 0.75000 0.25000 0.75000
K_POINTS automatic
8 8 8 0 0 0
total energy = -571.10793352 Ry/4 = -142.776983375
Thanks in advance for your help!
Very best,Giacomo
--
***************************************
Giacomo Giorgi, Ph.D.
Yamashita & Ushiyama Laboratory,
Department of Chemical System Engineering,
Faculty of Engineering,
The University of Tokyo.
tel&fax: +81-3-5841-7286
email: giacomo at tcl.t.u-tokyo.ac.jp
HP: http://www.tcl.t.u-tokyo.ac.jp/
***************************************
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Regards,
MOHNISH,
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Mohnish PandeyBTech-Mtech, IIT Kanpur
Senior Project Associate,
Department of Chemical Engineering,
IIT KANPUR, UP, INDIA
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