Quesiton about check sysmetry break

Zhang Xiaole · Post by **Zhang Xiaole** » Mon Jun 18, 2012 9:29 am

Dear users,
Recently, i want to calculate the crystal GaSe, which has 194 space group number (P 63/m m c), When i prepare the input file like this

Code: Select all

   natom 8
   ntypat 2
   znucl 31 34
   typat 1 1 1 1 2 2 2 2
   xred  0.333333  0.666667  0.177000
           0.333333  0.666667  0.323000
           0.666667  0.333333  0.823000
           0.666667  0.333333  0.677000
           0.333333  0.666667  0.600000
           0.333333  0.666667  0.900000
           0.666667  0.333333  0.400000
           0.6d6667  0.333333  0.100000

the corresponding output file will give a comment that

Code: Select all

symbrav : COMMENT -
  The Bravais lattice determined only from the primitive
  vectors, bravais(1)=  6, is more symmetric
  than the real one, iholohedry=  3, obtained by taking into
  account the atomic positions. Start deforming the primitive vector set

and give the space group number 63 (Cmcm).
when i check the reasons for the results, i find the varible 'tolsym' is setted to 1.0D-8 defoutly, so i change my input file like this

Code: Select all

   natom 8
   ntypat 2
   znucl 31 34
   typat 1 1 1 1 2 2 2 2
   xred  0.333333333  0.666666667  0.177000
         0.333333333  0.666666667  0.323000
         0.666666667  0.333333333  0.823000
         0.666666667  0.333333333  0.677000
         0.333333333  0.666666667  0.600000
         0.333333333  0.666666667  0.900000
         0.666666667  0.333333333  0.400000
         0.666666667  0.333333333  0.100000

Then the Abinit will regonize the right spgoup number, but the code stop with complain

Code: Select all

forrtl: severe (66): output statement overflows record, unit -5, file Internal Formatted Write

i think maybe there are something wrong with the symmetry, so i set the varible 'chksymbreak=0', then everything goes fine.
But, i have one question about the varible 'cheksymbreak'. the discriptiong of this varible said that, when use it in the DFPT and GW calculations, this will lead to a bad results. But i wonder how can i analyse the phonon mode if the system have a wrong spgroup number?
Please guide me how overcome this situation?
Thanks in advanced.

Cheers！
Sheleon

kengel · Post by **kengel** » Wed Jun 20, 2012 5:03 pm

Dear Sheleon,

Have you tried using the geometry builder with symmetry?

To do this, I would use these input parameters:
acell
angdeg 90 90 120
spgroup 194
brvltt -1
natom
natrd 2
typat
znucl
xred
1/3 2/3 -0.1
1/3 2/3 0.177 !Kristallografiya (1956) 1, p537-p541

where acell has the dimensions of the conventional unit cell. The "brvltt -1" tells abinit to build a primitive unit cell based on the space group information.

Hope this helps,
Kale

Zhang Xiaole · Post by **Zhang Xiaole** » Thu Jun 21, 2012 2:13 pm

kengel wrote:Dear Sheleon,

Have you tried using the geometry builder with symmetry?

To do this, I would use these input parameters:
acell
angdeg 90 90 120
spgroup 194
brvltt -1
natom
natrd 2
typat
znucl
xred
1/3 2/3 -0.1
1/3 2/3 0.177 !Kristallografiya (1956) 1, p537-p541

where acell has the dimensions of the conventional unit cell. The "brvltt -1" tells abinit to build a primitive unit cell based on the space group information.

Hope this helps,
Kale

Dear,Kale
Very appreciate for your reply, the method you mentioned i have tried before, when i set the parameter 'natom=8' , the code would complain that according to the symmetry , there are 'N' atom in the cell not the number 8.
Any suggestion?
Cheers!
Sheleon

kengel · Post by **kengel** » Thu Jun 21, 2012 5:10 pm

Dear Sheleon,

You're very welcome. When you get the error message about 'N' atoms, is 'N' a number or the letter N?

I tried a dummy calculation (same geometry but wrong elements and some arbitrary parameters) just now with spgroup 194, and it seemed to work with natom = 8. It can be confusing because natom is the number of atoms in the primitive cell, not the conventional cell. But in this case, I don't know why natom = 8 doesn't work for you. Are there any other error messages?

Please let me know if you figure out the problem. I've attached my input, in case that helps.

Regards,
Kale

Code: Select all

acell 3.750 3.750 15.995
angdeg 90 90 120
brvltt -1
spgroup 194
natom 8
natrd 2
ntypat 2
typat 1 2
znucl 20 50
xred 1/3 2/3 0.1736
     1/3 2/3 0.6015
nband 50
ecut 50
toldfe 0.000001 eV
nshiftk 1
shiftk 0.0 0.0 0.0
ngkpt 4 4 4
occopt 3
tsmear 0.01
nstep 15
!tolsym 0.00000001

Zhang Xiaole · Post by **Zhang Xiaole** » Mon Jun 25, 2012 6:57 am

Dear kengel
i am sry that give you the wrong messege about 'error' when using symmetry builder, the error is not about Natom, is about maybe some output array was overflowed. the error messeage is like 'forrtl: severe(66): output statement overflows record, unit -5, file Internal Formatted Write'
i think this is not someting wrong in input, but someting wrong with the compiling of the code.

Cheers!

Sheleon

Zhang Xiaole · Post by **Zhang Xiaole** » Wed Jun 27, 2012 8:15 am

Dear kengel
I have finally fixed my problem of using symmtry builder. Then reason is i make a mistake for the input parameter 'shiftk'. Since the system i am calculating is hexagonal, i should use the 'shiftk 0.0 0.0 0.5' instead of 'shiftk 0.5 0.5 0.5' which i used previously.
Thank you for your kind suggestions
They are very useful for me to understand the calculation deeply.

Cheers!

Sheleon

kengel · Post by **kengel** » Wed Jun 27, 2012 3:41 pm

Dear Sheleon,

Thank you for letting me know what the problem was. I'm glad that you figured it out!
-Kale

ABINIT Discussion Forums

Quesiton about check sysmetry break

Quesiton about check sysmetry break

Re: Quesiton about check sysmetry break

Re: Quesiton about check sysmetry break

Re: Quesiton about check sysmetry break

Re: Quesiton about check sysmetry break

Re: Quesiton about check sysmetry break

Re: Quesiton about check sysmetry break