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About the dipole moment in SrTiO3
Date: 2022/02/23 15:39
Name: Gurung

Hello OpenMx users,
I am new to the OpenMx. I tried to do some calculations randomly. I used the calculations for the SrTiO3. The system is centrosymmetric But I find the calculations shows large dipole moment.

What am I doing wrong? Part of the input file is as follows

Species.Number 3
<Definition.of.Atomic.Species
O O6.0-s2p2d1 O_PBE19
Sr Sr10.0-s3p2d2 Sr_PBE19
Ti Ti7.0-s3p2d1 Ti_PBE19
Definition.of.Atomic.Species>


Atoms.Number 5
Atoms.SpeciesAndCoordinates.Unit FRAC #
<Atoms.SpeciesAndCoordinates
1 O 0.5 0.5 0.0 3.0 3.0 0 0 0 0 0 off
2 O 0.5 0.0 0.5 3.0 3.0 0 0 0 0 0 off
3 O 0.0 0.5 0.5 3.0 3.0 0 0 0 0 0 off
4 Sr 0.0 0.0 0.0 5.0 5.0 0 0 0 0 0 off
5 Ti 0.5 0.5 0.5 6.0 6.0 0 0 0 0 0 off
Atoms.SpeciesAndCoordinates>
Atoms.UnitVectors.Unit Ang # Ang|AU
<Atoms.UnitVectors
3.943 0.0 0.0
0.0 3.943 0.0
0.0 0.0 3.943
Atoms.UnitVectors>


scf.XcType GGA-PBE # LDA|LSDA-CA|LSDA-PW|GGA-PBE
scf.SpinOrbit.Coupling OFF
scf.SpinPolarization NC # On|Off|NC
scf.ElectronicTemperature 300.0 # default=300 (K)
scf.energycutoff 210.0 # default=150 (Ry)
scf.EigenvalueSolver Band # DC|GDC|Cluster|Band
scf.Kgrid 16 16 16 # means n1 x n2 x n3
#scf.Generation.Kpoint regular # regular|MP
scf.Mixing.Type rmm-diis # Simple|Rmm-Diis|Gr-Pulay|Kerker|Rmm-Diisk
#----------following mixing can be changed during the running by making a new file in the current directory with sytem.name as mgn_SCF_keywords------
scf.maxIter 400 #default=40
scf.Min.Mixing.Weight 0.001 # default=0.001
scf.Max.Mixing.Weight 0.700 # default=0.40
scf.Init.Mixing.Weight 0.1 # default=0.30
scf.Mixing.History 30 # default=5 use large values
#scf.Kerker.factor 2 #automatically detected by the code; default=1.0
scf.Mixing.StartPulay 5 # default=6 increase large value if not converged
scf.Mixing.EveryPulay 1
scf.criterion 1.0e-10 # default=1.0e-6 (Hartree)
scf.Electric.Field 0.0 0.0 0.0 #default=0.0 0.0 0.0 GV/m
#------------------------------------------------------
scf.lapack.dste dstevx # dstevx|dstedc|dstegr,default=dstevx
#scf.Ngrid 32 32 32 # n1, n2 and n3 for a- b- and c- axes


# restart using *.rst
scf.restart off
HS.fileout off #on|off, default=off

MD.Type nomd # Nomd|Opt|NVE|NVT_VS|NVT_NH
# Constraint_Opt|DIIS| EF|BFGS|RF\|EF
MD.EvsLC.step 0.4
MD.maxIter 1 # default=1
MD.TimeStep 0.01 # default=0.5 (fs)
MD.Opt.criterion 1.0e-4 # default=1.0e-4 (Hartree/bohr)
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Re: About the dipole moment in SrTiO3 ( No.1 )
Date: 2022/02/23 18:35
Name: Naoya Yamaguchi

Hi,

You can't evaluate the dipole moment or electric polarization of "solids" from the out file or standard output. Instead, you need to use the `polB`; see a manual page of http://www.openmx-square.org/openmx_man3.9/node118.html .
The theoretical background is explained in a technical note of https://t-ozaki.issp.u-tokyo.ac.jp/ISS18/slides-1st/ISS2018_Ishii.pdf , for example.

Regards,
Naoya Yamaguchi
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Re: About the dipole moment in SrTiO3 ( No.2 )
Date: 2022/02/24 01:10
Name: Gurung

Hello Naoya,
Thank you. So, the dipole moment reported in the out file is irrelevant.

Best regards
Gautam
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