The different phase expression in abinit and MS

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The different phase expression in abinit and MS

Postby jlwindy » Sun Jan 27, 2019 9:50 am

Dear all
I am studying the physical properties of the monoclinic PZT material with abinit.I build a module.It shows the monoclinic and CM space group in MS and VESTA.
cif.file
data_3D\Atomistic
_audit_creation_date 2019-01-26
_audit_creation_method 'Materials Studio'
_symmetry_space_group_name_H-M 'CM'
_symmetry_Int_Tables_number 8
_symmetry_cell_setting monoclinic
loop_
_symmetry_equiv_pos_as_xyz
x,y,z
x,-y,z
x+1/2,y+1/2,z
x+1/2,-y+1/2,z
_cell_length_a 5.7760
_cell_length_b 5.7500
_cell_length_c 4.0890
_cell_angle_alpha 90.0000
_cell_angle_beta 90.5000
_cell_angle_gamma 90.0000
loop_
_atom_site_label
_atom_site_type_symbol
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_U_iso_or_equiv
_atom_site_adp_type
_atom_site_occupancy
O1 O 0.31000 0.23000 0.42000 0.00000 Uiso 1.00
Pb2 Pb 0.50000 0.50000 0.00000 0.00000 Uiso 1.00
Ti3 Ti 0.50000 -0.00000 0.50000 0.00000 Uiso 1.00
O4 O 0.50000 -0.00000 1.00000 0.00000 Uiso 1.00


VASP.file
3D\Atomistic
1.0
5.7760000229 0.0000000000 0.0000000000
0.0000000000 5.7500000000 0.0000000000
-0.0356828056 0.0000000000 4.0888445285
O Pb Ti
6 2 2
Direct
0.310000002 0.230000004 0.419999987
0.310000002 0.769999981 0.419999987
0.810000002 0.730000019 0.419999987
0.810000002 0.269999981 0.419999987
0.500000000 0.000000000 0.000000000
0.000000000 0.500000000 0.000000000
0.500000000 0.500000000 0.000000000
0.000000000 0.000000000 0.000000000
0.500000000 0.000000000 0.500000000
0.000000000 0.500000000 0.500000000


input.file
ndtset 2 # There are 2 datasets in this calculation

# Set 1 : Internal coordinate optimization

ionmov1 2 # Use BFGS algorithm for structural optimization
ntime1 60 # Maximum number of optimization steps
tolmxf1 1.0e-6 # Optimization is converged when maximum force
# (Hartree/Bohr) is less than this maximum


# Set 2 : Lattice parameter relaxation (including re-optimization of
# internal coordinates)

dilatmx2 1.15 # Maximum scaling allowed for lattice parameters
getxred2 -1 # Start with relaxed coordinates from dataset 1
getwfk2 -1 # Start with wave functions from dataset 1
ionmov2 2 # Use BFGS algorithm
ntime2 120 # Maximum number of optimization steps
optcell2 2 # Fully optimize unit cell geometry, keeping symmetry
tolmxf2 1.0e-6 # Convergence limit for forces as above
strfact2 100 # Test convergence of stresses (Hartree/bohr^3) by
# multiplying by this factor and applying force
# convergence test

#Common input data

#Starting approximation for the unit cell
acell 10.915 10.866 7.723 #this is a guess, with the c/a
#ratio based on ideal tetrahedral
#bond angles

angdeg 90.0 90.5 90.0
#Definition of the atom types and atoms
npsp 4
znucl 82 8 40 22
ntypat 3
ntypalch 1


mixalch 0.52 0.48
natom 10

typat 1 1 2 2 2 2 2 2 3 3

#Starting approximation for atomic positions in REDUCED coordinates
#based on ideal tetrahedral bond angles
xred 0.310000002 0.230000004 0.419999987
0.310000002 0.769999981 0.419999987
0.810000002 0.730000019 0.419999987
0.810000002 0.269999981 0.419999987
0.500000000 0.000000000 0.000000000
0.000000000 0.500000000 0.000000000
0.500000000 0.500000000 0.000000000
0.000000000 0.000000000 0.000000000
0.500000000 0.000000000 0.500000000
0.000000000 0.500000000 0.500000000

#Gives the number of bands, explicitely (do not take the default)
# For an insulator (if described correctly as an
# insulator by DFT), conduction bands should not
# be included in response-function calculations

#Definition of the plane wave basis set
ecut 30 # Maximum kinetic energy cutoff (Hartree)
ecutsm 0.5 # Smoothing energy needed for lattice paramete
# optimization. This will be retained for
# consistency throughout.
pawecutdg 36
#Definition of the k-point grid
ngkpt 4 4 4 # 4x4x4 Monkhorst-Pack grid
nshiftk 1 # Use one copy of grid only (default)
shiftk 0.0 0.0 0.0 # This choice of origin for the k point grid
# preserves the hexagonal symmetry of the grid,
# which would be broken by the default choice.

#Definition of the self-consistency procedure
diemac 4.0 # Model dielectric preconditioner
nstep 300 # Maxiumum number of SCF iterations
tolvrs 1.0d-18 # Strict tolerance on (squared) residual of the
# SCF potential needed for accurate forces and
# stresses in the structural optimization, and
# accurate wave functions in the RF calculations
# enforce calculation of forces at each SCF step
optforces 1

a part of out.file
DATASET 1 : space group P1 (# 1); Bravais aP (primitive triclinic)

I don't understand the reason that the space group is P1 triclinic in abinit.In MS and VESTE,the space group is CM monoclinic.

Looking forward to your reply.
jlwindy
jlwindy
 
Posts: 13
Joined: Tue Jan 08, 2019 5:11 pm

Re: The different phase expression in abinit and MS

Postby ebousquet » Sun Jan 27, 2019 11:54 am

Dear jlwindy,
OK, these CM/PM are from the cif file, not from abinit.
A first reason I see is that in your cif file you have the first atom at 0.31000 while in the input of abinit you have 0.310000002. The little 2 t the end could break the symmetry (the same applies for y and z directions). Either you are consistent between the two or you can keep the same input but reducing the tolsym of Abinit to 5-6 or so.
Best wishes,
Eric
ebousquet
 
Posts: 216
Joined: Tue Apr 19, 2011 11:13 am
Location: University of Liege, Belgium

Re: The different phase expression in abinit and MS

Postby jlwindy » Sun Jan 27, 2019 12:21 pm

dear eric
I charge the inputfile as you said.In log.flie, DATASET 1 : space group Pm (# 6); Bravais mP (primitive monocl.)
It's an important improvement.Thank you very much.Can you tell me the difference between Pm space group and Cm space group.
Looking forword to your reply.
Best wishes.
jlwindy
jlwindy
 
Posts: 13
Joined: Tue Jan 08, 2019 5:11 pm


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