[CP2K-user] [CP2K:20126] Symmetry recognization of primitive cells in CELL_OPT

[Lushan Wang]

Symmetry was not retained during cell-varied geometry optimization of an 
iodine single crystal (Space Group #64 - Cmce, 8 atoms in unit cell) with 
primitive cell (4 atoms). No matter we set "KEEP_SPACE_GROUP" and 
"KEEP_SYMMETRY" to be T or F, with or without set "SYMMETRY" to be 
"ORTHORHOMBIC" or even "MONOCLINIC_GAMMA_AB Monoclinic (a = b ≠ c, α = β = 
90°, γ ≠ 90°)" (as it is in 
https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/SUBSYS/CELL/CELL_REF.html) 
in $CELL, the symmetry was not maintained and became monoclinic or 
triclinic where it can't recognize the structure as a primitive cell of 
C-centered orthorhombic lattice any more.

My question: In cp2k, must we not use primitive cell for cell-varied 
structural optimization or am I too naive to set correct parameters to 
retain symmetry?

I've searched Google and conversations in cp2k group and didn't find 
relevant contents. Any help would be appreciated. Thanks!

PS: Original Cell information:
      &CELL
            A [angstrom]     3.7632537052    -2.2808521645     0.0000000000
            B [angstrom]     3.7632537052     2.2808521645     0.0000000000
            C [angstrom]     0.0000000000     0.0000000000     9.7061460000
         PERIODIC XYZ
 SYMMETRY MONOCLINIC_GAMMA_AB
      &END CELL
      &COORD
            I     0.0000000000     0.7474991182     1.1868772390
            I     0.0000000000     3.8142052109     8.5192687610
            I    -0.0000000000     1.5333530464     6.0399502390
            I     0.0000000000     3.0283512827     3.6661957610
      &END COORD

Methods:
Functional: PBE + DFT-D3(BJ)
Basis sets: DZVP-MOLOPT-SR-GTH
K-points: 8,8,3
CUTOFF and rel-CUTOFF: 400,50
EPS_SCF: 1E-6
EPS_DEFAULT: 1E-12

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