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**Questions and Answers / Symmetry detection problem: only the time reversal symemtry applies**

« **on:**June 10, 2021, 19:19 »

Dear ATK experts,

As a new user, I have a basic question concerning the symmetry operations for the nb of irreducible k-points.

I just runned the test example of Si bulk with

Can u explain why?

Thanks,

Dongzhe

PS: If I specify explicitly in MPgrid the symmetries by hand, I can reduce the k but this is rather impractical.

----------------------------

# Set up lattice

lattice = FaceCenteredCubic(5.4306*Angstrom)

# Define elements

elements = [Silicon, Silicon]

# Define coordinates

fractional_coordinates = [[ 0. , 0. , 0. ],

[ 0.25, 0.25, 0.25]]

k_point_sampling = MonkhorstPackGrid(

na=9,

nb=9,

nc=9,

)

------------------------

As a new user, I have a basic question concerning the symmetry operations for the nb of irreducible k-points.

I just runned the test example of Si bulk with

**9x9x9**k-points (see the basic parameters below), however, the code only detects the time-reversal symmetry, thus**Number of irreducible k-points: 365**...Can u explain why?

Thanks,

Dongzhe

PS: If I specify explicitly in MPgrid the symmetries by hand, I can reduce the k but this is rather impractical.

----------------------------

# Set up lattice

lattice = FaceCenteredCubic(5.4306*Angstrom)

# Define elements

elements = [Silicon, Silicon]

# Define coordinates

fractional_coordinates = [[ 0. , 0. , 0. ],

[ 0.25, 0.25, 0.25]]

k_point_sampling = MonkhorstPackGrid(

na=9,

nb=9,

nc=9,

)

------------------------