[Pw_forum] The resulte of optimizing the ZnO lattice constant use vc-relax
Eyvaz Isaev
eyvaz_isaev at yahoo.com
Tue Aug 19 16:20:39 CEST 2008
Dear user,
Please keep in mind that results of your calcultions might be different of experiment and other calculations due to many reasons. The main question is how much.
As concerns your results, they seem to be good, "a" parameter is just 1.1% elongated (3.287Ang against 3.25Ang), and c/a=1.627761723/1.011331020 = 1.6095 in quite good agreement with experimental.
> useful advice will be appreciated
And we will appreciate if you provide your affiliation.
Bests,
Eyvaz.
-------------------------------------------------------------------
Prof. Eyvaz Isaev,
Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia,
Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden
Condensed Matter Theory Group, Uppsala University, Sweden
Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com
--- On Tue, 8/19/08, wangqj1 <wangqj1 at 126.com> wrote:
> From: wangqj1 <wangqj1 at 126.com>
> Subject: [Pw_forum] The resulte of optimizing the ZnO lattice constant use vc-relax
> To: "pw_forum" <pw_forum at pwscf.org>
> Date: Tuesday, August 19, 2008, 5:30 PM
> Dear pwscf users
> I run vc-relax to optimize the lattice constant of
> ZnO unit cell,my input file and out file as follows:
>
> &CONTROL
> title = ZnOVC ,
> calculation = 'vc-relax' ,
> restart_mode = 'from_scratch' ,
> pseudo_dir =
> '/root/espresso-3.2.3/pseudo/' ,
> prefix = ZnO ,
> etot_conv_thr = 1.D-5 ,
> nstep = 100 ,
> tstress = .true. ,
> tprnfor = .true. ,
> dt = 100 ,
> tefield = .false. ,
> /
> &SYSTEM
> ibrav = 4,
> celldm(1) = 6.14161,
> celldm(3) = 1.6022,
> nat = 4,
> ntyp = 2,
> ecutwfc = 40 ,
> ecutrho = 300 ,
> nosym = .true. ,
> nbnd = 25,
> occupations = 'smearing' ,
> degauss = 0.002 ,
> smearing = 'methfessel-paxton'
> ,
> lda_plus_u = .false. ,
> /
> &ELECTRONS
> conv_thr = 1.D-8 ,
> startingpot = 'atomic' ,
> startingwfc = 'atomic' ,
> mixing_mode = 'plain' ,
> mixing_beta = 0.6 ,
> diagonalization = 'david' ,
> diago_full_acc = .true. ,
> /
> &IONS
> ion_dynamics = 'damp' ,
> /
> &CELL
> cell_dynamics = 'damp-w' ,
> /
> ATOMIC_SPECIES
> Zn 65.00000 Zn.pz-van_ak.UPF
> O 16.00000 O.pz-rrkjus.UPF
> ATOMIC_POSITIONS crystal
> Zn 0.333333333 0.666666667 0.000000000 1
> 1 1
> O 0.333333333 0.666666667 0.381700000 1
> 1 1
> Zn 0.666666667 0.333333333 0.500000000 1
> 1 1
> O 0.666666667 0.333333300 0.881700000 1
> 1 1
> K_POINTS automatic
> 4 4 4 0 0 0
>
> --------------------------------------------------------------------------------
> Program PWSCF v.3.2.2 starts ...
> Today is 18Aug2008 at 23: 7:36
> Ultrasoft (Vanderbilt) Pseudopotentials
> Current dimensions of program pwscf are:
> ntypx = 10 npk = 40000 lmax = 3
> nchix = 6 ndmx = 2000 nbrx = 14 nqfx = 8
> Title:
> ZnOVC
>
>
> bravais-lattice index = 4
> lattice parameter (a_0) = 6.1416 a.u.
> unit-cell volume = 321.4357 (a.u.)^3
> number of atoms/cell = 4
> number of atomic types = 2
> kinetic-energy cutoff = 40.0000 Ry
> charge density cutoff = 300.0000 Ry
> convergence threshold = 1.0E-08
> beta = 0.6000
> number of iterations used = 8 plain
> mixing
> Exchange-correlation = SLA PW PBE PBE (1434)
> nstep = 100
> celldm(1)= 6.141610 celldm(2)= 0.000000
> celldm(3)= 1.602200
> celldm(4)= 0.000000 celldm(5)= 0.000000
> celldm(6)= 0.000000
> crystal axes: (cart. coord. in units of a_0)
> a(1) = ( 1.000000 0.000000 0.000000 )
> a(2) = ( -0.500000 0.866025 0.000000 )
> a(3) = ( 0.000000 0.000000 1.602200 )
> reciprocal axes: (cart. coord. in units 2 pi/a_0)
> b(1) = ( 1.000000 0.577350 0.000000 )
> b(2) = ( 0.000000 1.154701 0.000000 )
> b(3) = ( 0.000000 0.000000 0.624142 )
>
> .......
> .......
> outfile:
>
> Final estimate of lattice vectors (input alat units)
> 1.011331020 0.000000000 0.000000000
> -0.505665507 0.875838356 0.000000001
> 0.000000000 -0.000000002 1.627761723
> final unit-cell volume = 334.0064 (a.u.)^3
> input alat = 6.1416 (a.u.)
> CELL_PARAMETERS (alat)
> 1.011331020 0.000000000 0.000000000
> -0.505665507 0.875838356 0.000000001
> 0.000000000 -0.000000002 1.627761723
> ATOMIC_POSITIONS (crystal)
> Zn 0.333333347 0.666666677 0.000438189
> O 0.333333356 0.666666677 0.380132292
> Zn 0.666666690 0.333333345 0.500438960
> O 0.666666695 0.333333331 0.880132483
>
> from the outfile I can see the c/a=1.627761723 and from the
> final unit-cell volume =334.0064 (a.u.)^3,I can compute the
> a=6.189678(Bohr)=3.2754(A)。From the value of caculating
> ,we can see that the c/a and a are both bigger than the
> experiment , I don't konw whether the result is right or
> wrong .
>
> Anybody who know about the question and give me the useful
> advice will be appreciated .
>
> Sincerely
>
>
>
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