[Wannier] Polarization of isolated H20 (dipole moment)
Pedro Augusto F. P. Moreira
pmoreira at ifi.unicamp.br
Mon Jul 2 20:42:01 CEST 2012
Dear all,
I have not calculated correctly yet the spontaneous polarization of a
water molecule as I mentioned in my last e-mail. Here, I gonna detail my
calculation steps and put my inputs and main output and hope that
someone could give any advice.
As I said, I did two simulation: (1) as Cantele suggested: my h2o.scf
input had tefield=.true. (it can be seen below); (2) And using th
Wannier funciton centres which I calculated with following sequence of
commands:
1) pw.x < h2o.scf >scf.out
2) pw.x < h2o.nscf >nscf.out
3) wannier90.x -pp h2o
4) pw2wannier90.x < h2o.pw2wan > pw2wan.out
5) wannier90.x h2o
My inputs and main outputs are bellow. The polarization, using WFs, were
calculated by the vectorial sum of ion positions times their atomic
number less twice the WF centre sum.
I repeated all calculations, using a "relax" command instead of "scf"
command in step 1. The positions used on the following inputs (h2o.nscf,
h2o.win and WF polarization calculations) were the relaxed atomic positions.
The polarizations, which I found, are:
Methods | Polarizations (Debye)
(1) tefield | 1.8179
(2) WFs | 1.8966
using 'relax' command:
(3) tefield | 1.7828
(4) WFs | 1.8544
Anyone knows why the polarization values are so discrepant. I note
that the discrepancies are greater if the atoms are dislocated to the
center of the cubic cell.
With best regards,
Pedro Moreira
##h2o.scf########################################
&control
calculation='scf', ! it was substituted for 'nscf' and
'relax' in calculations with these names
restart_mode='from_scratch',
pseudo_dir='/home/pedro/Documentos/espresso-5.0/pseudo',
outdir='/home/pedro/Documentos/espresso-5.0/exec1',
prefix='h2o',
tprnfor = .true.,
nstep = 500,
forc_conv_thr = 1.9e-4,
tefield=.true.
dipfield=.true.
/
&system
ibrav = 0,
nat = 3, ntyp = 2,
ecutwfc = 70.0, ecutrho = 700.0,
edir=3
eamp=0.D0
eopreg=0.1
emaxpos=0.5
/
&electrons
electron_maxstep = 500,
/
&ions
/
ATOMIC_SPECIES
H 1.00790 H.blyp-van_ak.UPF
O 15.9994 O.blyp-van_ak.UPF
ATOMIC_POSITIONS angstrom
O 0.0 0.0 0.0
H 0.77 0.0 0.62
H -0.77 0.0 0.62
CELL_PARAMETERS angstrom
10.6 0.00 0.00
0.00 10.6 0.00
0.00 0.00 10.6
K_POINTS {gamma}
##############################################
##scf.out#######################################
iteration # 6 ecut= 70.00 Ry beta=0.70
Davidson diagonalization with overlap
ethr = 4.01E-07, avg # of iterations = 2.0
negative rho (up, down): 0.293E-02 0.000E+00
Adding external electric field
Computed dipole along edir(3) :
Dipole 0.7152 Ry au, 1.8179 Debye
Dipole field 0.0011 Ry au
Potential amp. -0.0403 Ry
Total length 18.0280 bohr
total cpu time spent up to now is 134.0 secs
End of self-consistent calculation
k = 0.0000 0.0000 0.0000 ( 39751 PWs) bands (ev):
-24.8436 -12.5614 -9.1444 -7.1431
! total energy = -34.42311963 Ry
Harris-Foulkes estimate = -34.42315705 Ry
estimated scf accuracy < 0.00000072 Ry
##############################################
##h2o.win######################################
num_wann = 4
num_iter = 100
begin atoms_cart
O 0.0 0.0 0.0
H 0.77 0.0 0.62
H -0.77 0.0 0.62
end atoms_cart
begin projections
random
end projections
begin unit_cell_cart
10.6 0.00 0.00
0.00 10.6 0.00
0.00 0.00 10.6
end unit_cell_cart
mp_grid : 1 1 1
gamma_only : true
begin kpoints
0.0 0.0 0.0
end kpoints
##############################################
##h2o.pw2wan##################################
&inputpp
outdir = './'
prefix = 'h2o'
seedname = 'h2o'
spin_component = 'none'
write_mmn = .true.
write_amn = .true.
write_unk = .false.
/
##############################################
##h2o.wout_scf##################################
Writing checkpoint file h2o.chk... done
Final State
WF centre and spread 1 ( -0.000000, -0.257416, -0.127263 )
0.53681556
WF centre and spread 2 ( -0.399319, 0.000000, 0.338531 )
0.49244402
WF centre and spread 3 ( 0.399320, -0.000000, 0.338532 )
0.49244441
WF centre and spread 4 ( 0.000000, 0.257415, -0.127263 )
0.53681748
Sum of centres and spreads ( 0.000001, -0.000001, 0.422537 )
2.05852147
Spreads (Ang^2) Omega I = 1.816167784
================ Omega D = 0.000000000
Omega OD = 0.242353686
Final Spread (Ang^2) Omega Total = 2.058521470
------------------------------------------------------------------------------
Time for wannierise 0.012 (sec)
Writing checkpoint file h2o.chk... done
##############################################
##relax.out####################################
Computed dipole along edir(3) :
Dipole 0.7014 Ry au, 1.7828 Debye
Dipole field 0.0011 Ry au
Potential amp. -0.0395 Ry
Total length 18.0280 bohr
total cpu time spent up to now is 688.6 secs
End of self-consistent calculation
k = 0.0000 0.0000 0.0000 ( 39751 PWs) bands (ev):
-24.9139 -12.7725 -9.0391 -7.1487
! total energy = -34.42371576 Ry
Harris-Foulkes estimate = -34.42371607 Ry
estimated scf accuracy < 4.4E-10 Ry
The total energy is the sum of the following terms:
one-electron contribution = -64.27367874 Ry
hartree contribution = 33.58470996 Ry
xc contribution = -8.36936347 Ry
ewald contribution = 4.63384732 Ry
electric field correction = 0.00076917 Ry
convergence has been achieved in 4 iterations
Forces acting on atoms (Ry/au):
atom 1 type 2 force = -0.00001778 0.00000017 0.00004093
atom 2 type 1 force = -0.00002047 -0.00000010 -0.00001330
atom 3 type 1 force = 0.00003825 -0.00000007 -0.00002763
Total force = 0.000069 Total SCF correction = 0.000038
SCF correction compared to forces is large: reduce conv_thr to get
better values
bfgs converged in 6 scf cycles and 5 bfgs steps
(criteria: energy < 0.10E-03, force < 0.19E-03)
End of BFGS Geometry Optimization
Final energy = -34.4237157619 Ry
Begin final coordinates
ATOMIC_POSITIONS (angstrom)
O 0.000004575 -0.000000364 0.015670447
H 0.774640336 0.000000070 0.612163521
H -0.774644910 0.000000294 0.612166031
End final coordinates
#################################################
##h2o.wout_relax###################################
Writing checkpoint file h2o.chk... done
Final State
WF centre and spread 1 ( 0.000004, -0.255729, -0.113705 )
0.53766112
WF centre and spread 2 ( -0.400232, 0.000000, 0.346762 )
0.48541250
WF centre and spread 3 ( 0.400236, -0.000000, 0.346762 )
0.48540610
WF centre and spread 4 ( 0.000005, 0.255727, -0.113705 )
0.53766277
Sum of centres and spreads ( 0.000013, -0.000002, 0.466114 )
2.04614249
Spreads (Ang^2) Omega I = 1.801532201
================ Omega D = 0.000000000
Omega OD = 0.244610290
Final Spread (Ang^2) Omega Total = 2.046142491
------------------------------------------------------------------------------
##################################################
Em 29-06-2012 18:06, Pedro Augusto F. P. Moreira escreveu:
> Dear all.
>
> I am trying to calculate the spontaneous electric polarization of a
> single water molecule as a test.
> I am using Quantum Espresso (pw.x and wannier90). I did by two
> methods: (1) using tefield=.true. as suggested by Cantele
> (http://www.democritos.it/pipermail/pw_forum/2009-March/011936.html) and
> (2) by Wannier function centres (WF).
> I run a set of simulations with different initial atomic positions.
> The first simulation, I used the positions mentioned by Cantele and
> found P = 1.82 D and P =1.84 D by method (1). By WF, P= 1.90 D and 1.92
> D. The first values are calculated with BLYP functional and the second
> ones with PBE functional.
> After that, I moved initially all atoms by a vector (1.0 0.0 0.0)
> angstrom, relaxed the molecule and did again the calculations above. I
> found for Cantele way: P = 1.78 D and 1.80 D. By WF, P = 6.33 D and 6.37 D.
> My questions are:
>
> (a) I expected to find values closer to 1.87 D in all calculations,
> but all they are diverging from this value by, at least, 2 %. Should I
> really expect it ?
> (b) Anyone knows what can be happening in WF calculations when I moved
> the atoms? I know that if the atoms were moved beyond the unit cell, a
> constant factor would be summed to polarization. But, I think that is
> not my case because the dislocation vector was 1.0 A , while my cubic
> cell has 10.6 A edges.
>
> With best regards,
>
> Pedro
>
--
Pedro Moreira
IFGW - Unicamp - Brazil
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